Did Neolithic switch to agriculture drive selection for lighter skin colour in Europeans?

Study finds evidence of strong positive selection for skin, eye and hair pigmentation over last 5,000 years.

Why do people living in the tropics have dark skin whereas those living in higher latitudes have lighter skin? The traditional explanation is that is an evolutionary balancing trick between protection from skin cancer on one hand and the synthesis of Vitamin D by skin cells on the other. Dark skin results from higher levels of the pigment melanin: for those living nearer the equator, higher melanin levels provides a better protection from the sun’s more intense UV radiation; conversely, for those living at latitudes where UV radiation is weaker, the protection is not required and high melanin levels would block the production of Vitamin D.

However, things may not be quite so straightforward. A study carried out in 2012 at the University of Porto in Portugal considered alleles (variants) of four genes known to be associated with pigmentation, using samples taken from present-day Portuguese and sub-Saharan Africans. The evolutionary history of the four genes was estimated using a statistical model (Monte Carlo) to simulate the effects of genetic drift, natural selection and mutation. It was found that three of the alleles linked to lighter pigmentation did not start to sweep through European populations until around 11,000 to 19,000 years ago – at least 40,000 years after modern humans left Africa (Beleza, et al., 2012).

Two recently-published studies have investigated ancient DNA extracted from prehistoric human remains in Europe. The first study, published in the journal Nature, considered the pigment genes of DNA obtained from human remains found at the Mesolithic cave site of La Braña-Arintero, near León, Spain. The remains were identified as those of a male hunter-gatherer, who lived 7,000 years ago. He was found to have been dark-skinned and blue-eyed. Although present-day Spaniards are darker-skinned than northern Europeans, they are far paler than Africans (Olalde, et al., 2014). The result again suggests that paler skin colour was a fairly late development.

The second study, published in the journal PNAS, considered the pigment genes TYR, HERC2 and SLC45A2. TYR produces the enzyme tyrosinase, which is used as a catalyst in the production of melanin. HERC2 is responsible for determining eye colour; and SLC45A2 is involved in the distribution and processing of tyrosinase and other pigment-producing enzymes. The various alleles of these genes are responsible for different colours of skin, hair and eyes. Researchers extracted ancient DNA from 63 Chalcolithic (6500 to 5000 years old) and Bronze Age (5000 to 4000 years old) individuals from Ukrainian sites on the Pontic-Caspian steppe. 43 individuals yielded DNA from which the pigment genes could be sequenced, and these were compared with those of present-day Ukrainians.

The researchers found that the pigmentation of the prehistoric population differed from that of the present-day Ukrainians. The latter have 8.5 times as many alleles of TYR related to light skin colour as did their prehistoric forbears. Alleles of HERC2 related to blue eye colour were also far more common in the present-day population. However, none of these lighter pigmentation alleles are present in African populations. Thus it seems that the shift to lighter pigmentation was underway in the Chalcolithic and Bronze Ages, but it was at that stage incomplete – despite the immense passage of time since modern humans had left Africa. Computer simulations showed that these effects could not be explained by genetic drift alone, and that natural selection must have been a factor (Wilde, et al., 2014).

The team speculated that selection for lighter skin colour was related to the change in diet following the arrival of agriculture. The diet of hunter-gatherers was more likely than that of the farmers to include items rich in Vitamin D, such as fish and liver. To make up the difference, individuals needed to be able to synthesise it more efficiently – hence a lighter skin colour. At the same time, the trend to lighter hair and eye colour may have been the result of sexual selection: the initially-unusual colouring might have been more attractive to the opposite sex (the researchers noted that this phenomenon has been documented in guppies).

References:

1.  Beleza, S. et al., The timing of pigmentation lightening in Europeans. Molecular Biology and Evolution 30 (1), 24-35 (2012).

2.  Olalde, I. et al., Derived immune and ancestral pigmentation alleles in a 7,000-year-old Mesolithic European. Nature 507, 225-228 (2014).

3.  Wilde, S. et al., Direct evidence for positive selection of skin, hair, and eye pigmentation in Europeans during the last 5,000 y. PNAS (Early Edition) (2014).

Deep Impact?

Why an asteroid impact is unlikely to have caused the Late Quaternary mass extinction.

The Pleistocene world was dominated by large mammals, flightless birds and reptiles. These included mammoths, mastodons, giant ground sloths, camels, sabre-tooth cats, giant beavers, and giant deer with antlers spanning 3 m (10 ft.). In Australia, there lived the hippopotamus-sized Diprotodon optatum that weighed in at 2.8 tonnes, and was the largest marsupial of all time. These animals are collectively known as the megafauna, a term applied to animals with an adult weight of 45 kg (100 lb.) or more. Between 50,000 and 10,000 years ago, many of these great beasts vanished in one of the largest extinction events since the demise of the dinosaurs. Australia and the Americas were hardest hit, but no habitable continent remained unscathed. Overall, about 180 large mammal species and over 100 entire genera perished (Barnosky, et al., 2004; Lyons, et al., 2004; Koch & Barnosky, 2006; Barnosky, 2008). Usually referred to as the Late Quaternary extinction event, it was recognised by early geologists towards the end of the eighteenth century.

The cause of this mass extinction has long been debated and there remains a lack of consensus to this day. Climate change and human activity were put forward as possible causes as far back as the early nineteenth century, and both are hotly championed to this day. One of the more controversial theories, first proposed in 2007, is that around 12,900 years ago, Earth suffered multiple airbursts and surface impacts from fragments of a comet or asteroid that had previously broken up in space. In North America, the bombardment caused devastating shock-waves and continent-wide forest fires that brought about the extinction of the megafauna. While the overall effects were far less severe than those of the impact now believed to have killed off the dinosaurs, they were still sufficient to trigger a global ‘impact winter’. This in turn precipitated Younger Dryas climatic downturn.

Evidence for the supposed impact was claimed in the form of a 12,900-year-old carbon-rich layer or ‘black mat’. The layer has been identified at around fifty Clovis sites in North America. It is said to contain material consistent with an impact, including magnetic mineral grains, soot, carbon spherules and so-called nanodiamonds. The latter are minute diamonds formed when carbon particles are subjected to intense heat and pressure by an explosion (Firestone, et al., 2007; Haynes, 2008; Kennett, et al., 2009). More recently, evidence for impacts has also been claimed from Younger Dryas boundary sites in Mexico, Belgium, the Netherlands, Germany and Syria (Israde-Alcántara, et al., 2012; Bunch, et al., 2012). Anomalous levels of platinum, said to be due to the impact of a large iron meteorite, have also been reported from Greenland ice core samples dating to the Younger Dryas boundary (Petaev, et al., 2013).

In theory this is all sounds highly feasible, but in practice the timing is a little suspicious. Other factors were in play at the time, and it is not necessary to invoke an extraterrestrial impact to explain the onset of the Younger Dryas. Named for the arctic-alpine flowering plant Dryas octopetala that flourished in the northern tundra at that time, the Younger Dryas marks the final stage of the Pleistocene. It lasted from 12,900 until 11,600 years ago and both its onset and termination were fairly abrupt (Taylor, et al., 1997; Severinghaus, et al., 1998). During the preceding Bølling-Allerød warm period, the North American ice sheets retreated. The resulting meltwater formed a vast glacial lake known as Lake Agassiz, larger than all the modern Great Lakes put together. Beginning 13,000 years ago, Lake Agassiz released a series of freshwater discharges into the Arctic Ocean, through what is now the drainage basin of the Mackenzie River (Murton, et al., 2010). The conventional view is that the great volume of freshwater disrupted the Gulf Stream, halting the flow of warm seawater from the tropics to higher latitudes. The result was to plunge the Northern Hemisphere back into glacial conditions. Effects in the Southern Hemisphere are less certain, though evidence of cooling has been found there also (Moreno, et al., 2001).

That an extraterrestrial impact should occur at more or less the same time as the freshwater discharge strikes me as being a rather implausible coincidence. It should also be noted that other studies have failed to find evidence for the nanodiamonds (Daulton, et al., 2010), and that there is no evidence for the continent-wide conflagration supposedly triggered by the impact. Evidence for burning is better attributed to climate change-generated increases in natural wildfires (Marlon, et al., 2009). Similarly, the magnetic grains can be accounted for by a constant influx of micrometeorites from space (Surovell, et al., 2009). The ‘black mats’ do not occur throughout the whole of North America, but rather are located predominantly in the west. They may be algal mats or ancient soils associated with regional increases in moisture (Gill, et al., 2012). The source of platinum anomaly may be extraterrestrial, but this remains unproven and more evidence is needed. All in all, I am sceptical about the impact theory, although it certainly cannot be ruled out.

References:

1. Barnosky, A., Koch, P., Feranec, R., Wing, S. & Shabel, A., Assessing the Causes of Late Pleistocene Extinctions on the Continents. Science 306, 70-75 (2004).

2. Lyons, K., Smith, F. & Brown, J., Of mice, mastodons and men: human-mediated extinctions on four continents. Evolutionary Ecology Research 6, 339–358 (2004).

3. Koch, P. & Barnosky, A., Late Quaternary Extinctions: State of the Debate. The Annual Review of Ecology, Evolution, and Systematics 37, 215–250 (2006).

4. Barnosky, A., Megafauna biomass tradeoff as a driver of Quaternary and future extinctions. PNAS 105 (Suppl. 1), 11543–11548 (2008).

5. Firestone, R. et al., Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling. PNAS 104 (41), 16016–16021 (2007).

6. Haynes, V., Younger Dryas ‘‘black mats’’ and the Rancholabrean termination in North America. PNAS 105 (18), 6520–6525 (2008).

7. Kennett, D. et al., Nanodiamonds in the Younger Dryas Boundary Sediment Layer. Science 323, 94 (2009).

8. Israde-Alcántara, I. et al., Evidence from central Mexico supporting the Younger Dryas extraterrestrial impact hypothesis. PNAS 109 (13), E738-E747 (2012).

9. Bunch, T. et al., Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago. PNAS 109 (28), E1903-E1912 (2012).

10. Petaev, M., Huang, S., Jacobsen, S. & Zindler, A., Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas. PNAS 110 (32), 12917-12920 (2013).

11. Taylor, K. et al., The Holocene–Younger Dryas Transition Recorded at Summit, Greenland. Science 278, 825-827 (1997).

12. Severinghaus, J., Sowers, T., Brook, E., Alley, R. & Bender, M., Timing of abrupt climate change at the end of the Younger Dryas interval from thermally fractionated gases in polar ice. Nature 391, 141-146 (1998).

13. Murton, J., Bateman, M., Dallimore, S., Teller, J. & Yang, Z., Identification of Younger Dryas outburst flood path from Lake Agassiz to the Arctic Ocean. Nature 464, 740-743 (2010).

14. Moreno, P., Jacobson, G., Lowell, T. & Denton, G., Interhemispheric climate links revealed by a late-glacial cooling episode in southern Chile. Nature 409 , 804-808 (2001).

15. Daulton, T., Pinter, N. & Scott, A., No evidence of nanodiamonds in Younger–Dryas sediments to support an impact event. PNAS 107 (37), 16043-16047 (2010).

16. Marlon, J. et al., Wildfire responses to abrupt climate change in North America. PNAS 106 (8), 2519–2524 (2009).

17. Surovell, T. et al., An independent evaluation of the Younger Dryas extraterrestrial impact hypothesis. PNAS 106 (43), 18155-18158 (2009).

18. Gill, J. et al., Paleoecological changes at Lake Cuitzeo were not consistent with an extraterrestrial impact. PNAS 109 (34), E2243 (2012).

Return from Beringia

Linguistic study suggests Ice Age groups migrated back to Central Asia from Bering land bridge.

The New World was the last habitable part of the globe to be settled by humans. Today, Alaska is separated from eastern Siberia by the Bering Strait, which is 55 km (18 miles) wide, but this has not always been the case. Throughout the period from 25,000 years ago until as late as 10,000 years ago, sea levels were so low that the strait and parts of the adjoining Chukchi and Bering Seas became dry land. The result was a landmass stretching from the Verkhoyansk Range in eastern Siberia to the Mackenzie River in northwestern Canada (Hoffecker, et al., 1993). Known as Beringia, this so-called ‘land bridge’ was 1,600 km (1,000 miles) from north to south and linked Asia to North America. The region remained dry and cold, but free of ice. It is thought to have been an open landscape covered with grasses and herbaceous tundra and steppe vegetation (Guthrie, 2001; Zazula, et al., 2006). It is via the Beringia land bridge that humans are long believed to have first reached the New World, but the number of migrations and their timing have been hotly debated for many decades.

Much of our understanding of these migrations has come from archaeological and genetic data. The genetic results suggest that the New World was populated in three migrations: a major migration associated with the First Americans or Paleoindians; a second migration associated with Na-Dene language speakers distributed mainly in northwestern Canada, Alaska and along the Pacific Coast; and a third migration associated with Eskimo-Aleut language speakers, who are restricted to the Aleutian Islands and the Arctic (Reich, et al., 2012).

A third approach to understanding prehistoric migrations is comparative linguistics. In 1986, the American linguist Joseph Greenberg (1986) used this method in an attempt to identify the number of migrations into the New World. It has long been known that languages evolve over time, and that there are language ‘families’ or groups of languages that share common origins. Greenberg began by assuming each group of migrants spoke their own language and that over time a language family arose from each founding language. In earlier work going back to the 1960s, Greenberg claimed that there were three language families: Amerind, Na-Dene and Aleut-Eskimo. His conclusion – now vindicated by genetics – is that there were three migrations.

Up until now, however, linguists have been unable to link the three language groups to those in Asia. It has long been suspected that there is a linguistic connection between the Na-Dene languages and the Yeniseian languages of Siberia, but it remains unproven. A new study has investigated the possible relationship, using phylogenetic methods to build up a linguistic family tree. In the last decade, computational phylogenetic tools developed primarily to study relationships in evolutionary biology have been adapted for use in the field of historical linguistics. These new techniques have been used to study prehistoric migrations and language classifications as far back as the latter part of the last Ice Age.

The researchers applied the technique to 40 languages spoken across North America and Asia. The resulting family tree was used to test various migration hypotheses. The results suggested that there was an early dispersal of Na-Dene populations along the North American coast and a Yeniseian migration back into Siberia. This was followed by a dispersal of Na-Dene languages into the North American interior. The study does not contradict the widely-accepted scenario that the New World was settled from Beringia, but complicates it with the insight that some groups in Beringia migrated back in the opposite direction (Sicoli & Holton, 2914).

References:

1. Hoffecker, J., Powers, R. & Goebel, T., The Colonization of Beringia and the Peopling of the New World. Science 259, 46-53 (1993).

2. Guthrie, D., Origin and causes of the mammoth steppe: a story of cloud cover, woolly mammal tooth pits, buckles, and inside-out Beringia. Quaternary Science Reviews 20, 549-574 (2001).

3. Zazula, G. et al., Vegetation buried under Dawson tephra (25,300 14C years BP) and locally diverse late Pleistocene paleoenvironments of Goldbottom Creek, Yukon, Canada. Palaeogeography, Palaeoclimatology, Palaeoecology 242, 253–286 (2006).

4. Reich, D. et al., Reconstructing Native American population history. Nature 488, 370–374 (2012).

5. Greenberg, J., Turner, C. & Zegura, S., The Settlement of the Americas: A Comparison of the Linguistic, Dental, and Genetic Evidence. Current Anthropology 27 (5), 477-497 (1986).

6. Sicoli, M. & Holton, G., Linguistic Phylogenies Support Back-Migration from Beringia to Asia. PLoS One 9 (3), e91722 (2914).

Chauvet cave paintings may be far more recent than generally believed

French archaeologists claim that prehistoric artwork thought to be 36,000 years old is actually 10,000 years younger.

Chauvet Cave is located near the village of Vallon-Pont-d’Arc, Ardèche in southern France. The cave was discovered in 1994 by a team of cavers led by Jean-Marie Chauvet, for whom the site was named. It was the most important cave painting find since the discovery of Lascaux by a group of teenagers during World War II. Unlike the 18,000-year-old Lascaux cave paintings, which became a major tourist attraction after the war and deteriorated badly as a result, Chauvet was rapidly taken over by the French government and a strict conservation program was put in hand.

The artwork comprises 425 panels, depicting rhinoceroses, lions, bears, mammoths, horses, bison, ibex, reindeer, red deer, aurochs, muskoxen, panthers, and the earliest-known representation of an owl turning its head through 180 degrees. Hand prints, red dots and a partial image of a woman associated with a bison have also been discovered.

Radiocarbon dates indicating that the paintings are around 36,000 years old are widely accepted. This would date them to the late Aurignacian period, and make them twice as old as Lascaux. Put another way, the radiocarbon dates suggest that Lascaux is separated from Chauvet by the same interval of time that separates it from the first landing on the Moon. However, archaeologists Jean Combier and Guy Jouve have cast doubt on the great antiquity of the Chauvet paintings.

They argue that on stylistic grounds, the Chauvet artwork cannot be associated with the Aurignacian period. Instead, they claim, the artwork shows affinities to that of the more recent Gravettian and Solutrean periods. Therefore the oldest paintings at Chauvet cannot be more than 26,000 years old. The later ones might even be contemporary with Lascaux.

That Chauvet dates to the Solutrean period was the initial impression of Jean Clottes, one of France’s most eminent prehistorians. Clottes made his assessment in 1995, before any radiocarbon dates were available. His dating of the artwork on purely stylistic grounds was subsequently dismissed as ‘foolhardy’ – but could it be that relying purely on radiocarbon dates is equally unwise?

When first introduced in the 1950s, radiocarbon dating revolutionised archaeology and Willard Libby, the American chemist who pioneered the technique, was awarded the Nobel Prize in Chemistry in 1960. However, radiocarbon dating is not infallible. For example, it is very easy for a sample to become contaminated with more recent organic material that will slew results.

In the case of Chauvet, radiocarbon dates were obtained from wood charcoal used as black pigment. However, Combier and Jouve suggest fossil carbon was used as well as charcoal. This was available at Vagnas, a village not far from Vallon-Pont-d’Arc, where there was a quarry yielding lignite and bitumen. A pigment comprising a mixture of fresh charcoal and fossil carbon would present as being significantly older than one containing fresh charcoal alone.

Combier and Jouve note that such a mixture would also have a different isotopic signature to that of pure wood charcoal, i.e. the proportions of the stable carbon isotopes carbon-12 and carbon-13 would differ between the two. It would thus be possible to show whether or not the Chauvet dates were suspect. Such an anomaly has been detected at another cave site, Candamo Cave in Spain, although in this case the ‘old’ carbon leeched into the pigment from the limestone walls of the cave through the action of bacteria.

Accordingly, Combier and Jouve suggest that fresh radiocarbon dates should be obtained for Chauvet, and they believe that it extremely important that more than one laboratory carries out the work.

References:

1. Clottes, J., Cave Art (Phaidon, New York, 2008).
2. Combier, J. & Jouve, G., Chauvet cave’s art is not Aurignacian: a new examination of the archaeological evidence and dating procedures. Quartär 59, 131-152 (2012).
3. Combier, J. & Jouve, G., Nouvelles recherches sur l’identité culturelle et stylistique de la grotte Chauvet et sur sa datation par la méthode du 14C. L'Anthropologie ( (in press) doi:10.1016/j.anthro.2013.12.001) (2014).
4. Mellars, P., A new radiocarbon revolution and the dispersal of modern humans in Eurasia. Nature 493, 931-935 (2006).

Study provides insight into diet of early Pacific colonists

Lapita people relied on foraging as well as agriculture; men enjoyed a more varied diet than women.

Between 1400 and 800 BC, Polynesian colonists associated with the Lapita culture spread out into the Pacific from Island Southeast Asia, eventually settling the islands of central and eastern Melanesia and western Polynesia. The word ‘Lapita’ is a Western mispronunciation of Xapeta’a, the native Kanak name for the site in New Caledonia that gave its name to the culture. The Lapita culture is noted for its distinctive pottery, which was typically red-slipped, and decorated with small-toothed (‘dentate’) bone or shell chisels.

By around 1300 to 1200 BC, Early Lapita communities were established over a wide area of the Bismarck Archipelago. The dispersed communities formed a network of societies that maintained regular contact with one another, and were probably related by kinship and marriage. The clearest evidence for these long-distance interactions is the trade in obsidian from New Britain and the Admiralty Islands, and parallel changes in pottery styles over the region up until around 1000 BC. After that time, inter-island contacts seem to have dropped off markedly. In the meantime, by around 1200 to 1100 BC, Lapita people had moved beyond the Bismarck Archipelago and settled parts of Remote Oceania. In just 600 years, the Lapita people spread through Melanesia to the Central Pacific, reaching Vanuatu by 1000 BC, Fiji and Tonga by 900 BC, and Samoa by 700 BC. It was here that the migration paused after covering some 5,500 km (3,400 miles), one of the fastest movements of a prehistoric colonising population on record.

The Lapita colonists brought with them domesticated pigs, chickens and dogs, and crops including yams, taro, breadfruit, coconut, sago and bananas. However, the extent to which they relied upon this ‘agricultural package’ for sustenance remains uncertain, and in particular there are questions about how settlers sustained themselves during the initial stages of colonisation of each island.

A powerful technique for understanding the diets of prehistoric peoples is stable isotope analysis. The ratios in which isotopes of certain elements occur in human remains are dependent on what individuals ate while they were alive. Investigations have focussed on stable (i.e. non-radioactive) isotopes of carbon and nitrogen and, more recently, sulphur.

In the case of the Lapita people such investigations have been hampered by a scarcity of human remains, despite around 250 sites being known throughout the western Pacific. However, a cemetery at the site of Teouma, on Efate Island, Vanuatu has yielded 68 burials – the largest number of human remains from the Lapita period ever found. The cemetery dates to the earliest known settlement of Central Vanuatu, around 1000 BC. As such, it can provide information about the settlers’ diet during the initial stages of Lapita colonisation.

The researchers obtained isotopic ratios for bone collagen from 51 adult Lapita people. They then obtained a comprehensive isotopic dietary baseline made up of both modern plants and animals, and prehistoric animal remains from the site. By comparing the two sets of results, they found that the settlers’ diet included reef fish, marine turtles, and fruit bats in addition to domesticated pigs and chickens. Rather than rely solely on their ‘transported landscape’ of domesticated crops and animals, the settlers were practicing a mixed subsistence that included significant quantities of native wildlife, as well as domestic animals.

Dietary differences were found between men and women. The men enjoyed a more varied diet, which included greater access to pigs, chicken and tortoises. Such foods are considered to be of high status in present-day Pacific island societies, and the difference may reflect a higher status for men in Lapita society.

The results are consistent with the view that a newly-established colony would not be able to produce enough food to support itself, and would have to rely to an extent on foraging. This is also supported by an analysis of the remains of domestic pigs and chickens, which suggested that they were reared as free range animals. Such a system of husbandry would reduce demand for the limited amount of plant food that was available.

Reference:

1. Kinaston, R. et al., Lapita Diet in Remote Oceania: New Stable Isotope Evidence from the 3000-Year-Old Teouma Site, Efate Island, Vanuatu. PLoS One 9 (3), e90376 (2014).

Were multiple early human species living in Georgia, 1.85 million years ago?

New skull with ‘enigmatic’ jawbone and differing tool technologies suggests that two different hominin groups are represented by Dmanisi remains.

The former Soviet republic of Georgia is located at the crossroads of Europe and Asia. Lying on the eastern shores of the Black Sea, it was the destination of Jason and the Argonauts in their quest for the Golden Fleece, but long before this it was a stopping point for the earliest-known hominin migration out of Africa. In 1984, stone tools were discovered at the small medieval town of Dmanisi in the southeast of the country, 93 km (58 miles) southwest of the capital, Tbilisi. Archaeologists broke through the foundations of a medieval building into an ancient river deposit, where simple stone tools resembling those made by the earliest humans were found with the bones of extinct mammals. 

During the 1990s, the remains of early humans were recovered, including two partial skulls and a lower jawbone. The fossils were dated by palaeomagnetic, potassium-argon and argon-argon methods, giving an age for the remains of 1.77 million years old (Gabunia, et al., 2000). Subsequent dating of the stone tools indicated that the site was first occupied 1.85 million years ago, and that repeated occupations continued over a period of 80,000 years. There was evidently a long-term human presence in the Caucasus at around or even before the time of the earliest evidence for Homo erectus in Africa (Ferring, et al., 2011).

There have been a number of subsequent discoveries of human remains at the site. These include the skull, lower jawbone and partial skeleton of an adolescent (Vekua, et al., 2002; Lordkipanidze, et al., 2007); the skulls and lower jawbones of two adults (Lordkipanidze, et al., 2006; Lordkipanidze, et al., 2013); and postcranial bones from three other individuals, all adults (Lordkipanidze, et al., 2007). One of the skulls belonged to an elderly male who had lost all but one of his teeth some years prior to his death. He could not have survived unaided and must have been cared for by his companions throughout those last years of his life (Lordkipanidze, et al., 2005; Lordkipanidze, et al., 2006). The other skull, the fifth to be discovered at the site and hence known as Skull 5, is characterised by a large face and thick browridges. Skull 5 is complete and undeformed; it is the only known fully-preserved adult hominin skull from the early Pleistocene (Lordkipanidze, et al., 2013).

From the various remains, body size metrics have been estimated for the Dmanisi hominins. They were 1.45 to 1.66 m (4 ft. 9 in. to 5 ft. 5 in.) tall and weighed 40.0 to 50.0 kg (88 to 110 lb.). The cranial capacities of the five skulls range from 546 to 730 cc, about half that of a modern human. The encephalization quotient (a measure of brain size in relation to body size) lies in the range from 2.4 to 3.13; a figure that is at the lower end of the estimates for African Homo erectus, and is more comparable to that of Homo habilis or Australopithecus (Lordkipanidze, et al., 2007; Lordkipanidze, et al., 2013).

The Dmanisi hominins display a mosaic of primitive and derived (more modern) features. Their limb proportions were similar to those of a modern human. The lower limbs and feet were essentially modern, although the feet turned slightly inwards. On the other hand, the forearm lacked what is known as humeral torsion. In modern humans, the elbow joint is typically rotated relative to the shoulder joint, so that the forearm naturally hangs with the palms facing inwards; but the Dmanisi forearm lacked this rotation, so their palms were oriented more forwards. The inward-turning feet, lack of humeral torsion, small body size and small brain size may be seen as primitive traits, sharing more in common with Homo habilis than with Homo erectus (Lieberman, 2007; Lordkipanidze, et al., 2007). 

Initially assigned to African Homo erectus (Vekua, et al., 2002), the Dmanisi hominins were later put forward as a new human species, Homo georgicus (Gabunia, et al., 2002); though this proposal has since been retracted (Lordkipanidze, et al., 2013), and it has been suggested that early African Homo erectus was not only quite widespread, but also unusually variable in both body and brain size, and also less modern than sometimes supposed (Lieberman, 2007).

Two more radical (and diametrically-opposed) possibilities have recently been put forward. The first is that the various species often proposed for early African Homo (Homo habilis, Homo rudolfensis, Homo ergaster and Homo erectus) were all actually variants of the same species, and that early Homo was a single lineage which evolved over time without differentiating into multiple species. This conclusion is based on a claim that shape variation between the five Dmanisi skulls is roughly the same as that seen among the various early Homo skulls from East Africa, even though the former represents a single species and the latter are generally thought to represent several (Lordkipanidze, et al., 2013).

The second proposal (Bermúdez de Castro, et al., 2014) is that Skull 5 represents a different group of early hominins to that of the other Dmanisi remains. The lower jawbone is larger than those of others, and is said to represent a ‘large and somewhat enigmatic individual’. Its shape differs, and the differences cannot be accounted for in terms of body size or sex. It possesses a mosaic of primitive and derived features that are absent from other Dmanisi specimens. Furthermore, patterns of dental wear suggest a higher intake of fibrous and abrasive foods. It has accordingly been suggested that the jawbone is adapted to a different ecological niche to the other Dmanisi hominins, and that it represents a different species.

Although tools document a long-term human presence at Dmanisi, all the actual human remains were found in the same geological layer. This makes the ‘two species’ scenario problematic, as it implies that both species lived at about the same time. However, the stratigraphy of Dmanisi is complex, and it is possible that the fossil remains were re-deposited in the same geological layer after initially occupying sediments of different ages. It has also been claimed that the tools found at Dmanisi are consistent with the existence of two different populations.

More evidence is needed to determine just where the Dmanisi hominins fit into the broader human evolutionary picture, but it is becoming clear that the first hominin dispersal out of Africa was a far more complex process than was at one time supposed.

References:

1. Gabunia, L. et al., Earliest Pleistocene Hominid Cranial Remains from Dmanisi,Republic of Georgia: Taxonomy, Geological Setting, and Age. Science 228, 1019-1025 (2000).

2. Ferring, R. et al., Earliest human occupations at Dmanisi (Georgian Caucasus) dated to 1.85–1.78 Ma. PNAS 108 (26), 10432-10436 (2011).

3. Vekua, A. et al., A New Skull of Early Homo from Dmanisi, Georgia. Science 297, 85-89 (2002).

4. Lordkipanidze, D. et al., Postcranial evidence from early Homo from Dmanisi, Georgia. Nature 449, 305-310 (2007).

5. Lordkipanidze, D. et al., A Fourth Hominin Skull From Dmanisi, Georgia. The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology 288A, 1146–1157 (2006).

6. Lordkipanidze, D. et al., A Complete Skull from Dmanisi, Georgia, and the Evolutionary Biology of Early Homo. Science 342, 326-331 (2013).

7. Lordkipanidze, D. et al., The earliest toothless hominin skull. Nature 434, 717-718 (2005).

8. Lieberman, D., Homing in on early Homo. Nature 449, 291-292 (2007).

9. Gabunia, L., de Lumley, M.-A., Vekua, A., Lordkipanidze, D. & de Lumley, H., Découverte d'un nouvel hominidé à Dmanissi (Transcaucasie, Géorgie). C.R. Palévol. 1, 243–253 (2002).

10. Bermúdez de Castro, J., Martinón-Torres, M., Sier, M. & Martín-Francés, L., On the Variability of the Dmanisi Mandibles. PLoS One 9 (2), e88212 (2014).

Human footprints up to one million years old discovered at Happisburgh, Norfolk

Human footprints up to one million years old discovered at Happisburgh, Norfolk

Footprints left by small group of adults and children are oldest discovered outside Africa

Human footprints dating to between one million and 780,000 years old have been reported on the beach of the coastal village of Happisburgh, Norfolk (pronounced ‘Hazeborough’), and are the earliest-known direct evidence for the presence of humans in northern Europe. The footprints briefly emerged at low tide in May 2013, having being exposed by rough seas.

Within a fortnight, they had vanished again – but not before a team led by Nick Ashton from the British Museum had obtained plaster casts and 3d images. A total of 152 footprints were recorded, of which twelve yielded complete outlines suitable for analysis. It is thought that these twelve footprints represented five individuals ranging in height from 0.93 to 1.73 m (3 ft. 0 in. to 5 ft. 8 in.), suggesting the presence of both adults and children. It has been suggested that the Happisburgh hominins are related to Homo antecessor (‘Pioneer man’), a human species known from Sierra de Atapuerca in northern Spain during the period between 1.2 million and 800,000 years ago (Ashton, et al., 2014).

Early humans from this period are broadly categorised as Homo erectus. In Europe, Homo erectus was later replaced by the larger-brained Homo heidelbergensis, which might have been the forerunner of the Neanderthals in Europe and modern humans in Africa.

The Happisburgh footprints are the earliest direct evidence for humans in Britain, but tools used by these first Britons have been coming to light since 2005, when 700,000-year-old flint artefacts were reported from Pakefield in Suffolk (Parfitt, et al., 2005). In 2010 even earlier flint artefacts were reported from Happisburgh, estimated to be at least 780,000 years old, and probably older (Parfitt, et al., 2010). Previously, the earliest uncontested evidence for humans in northern Europe dated to no earlier than around 500,000 years ago (Parfitt, et al., 2005).

Analysis of animal remains suggests the Happisburgh people occupied the edges of forests at what was then an estuary of the River Thames, and lived towards the end of a warm interglacial period. It is not certain when the interglacial occurred, but there were warm periods from 866,000 to 814,000 years ago, and from 970,000 to 936,000 years ago (Parfitt, et al., 2010).

Britain was at this time connected to the mainland and lying on the southern edge of the forests of northwestern Europe. The climate was similar to that of today and while comfortable by British standards, it would have been chilly for those used to a Mediterranean or African climates. It remains unclear whether expansion into northern latitudes with lower winter temperatures required human physical adaptation, seasonal migration or developments in technology such as hunting, clothing, the use of shelters and the control of fire (Parfitt, et al., 2005; Parfitt, et al., 2010; Roberts & Grun, 2010).

References:
1. Ashton, N. et al., Hominin Footprints from Early Pleistocene Deposits at Happisburgh, UK. PLoS One 9 (2) (2014).
2. Parfitt, S. et al., The earliest record of human activity in northern Europe. Nature 438, 1008-1012 (2005).
3. Parfitt, S. et al., Early Pleistocene human occupation at the edge of the boreal zone in northwest Europe. Nature 466, 229-233 (2010).
4. Roberts, A. & Grun, R., Early human northerners. Nature 466, 189 (2010).

Reassessment of 1950s fossil find provides early evidence for hominins in Central Africa

2.0 to 2.6-million-year-old tooth is from australopithecine or early human.

A reassessment of a fossil tooth from an old archaeological collection suggests that early hominins had extended their range to the western branch of Africa’s Great Rift Valley by no later than two million years ago. Since the late 1950s, large numbers of early hominin fossils have been found in the eastern branch of the Great Rift Valley, which is often described as the Cradle of Humanity. However, up until now, none have been found in the western branch.

Ishango 11 is an archaeological site in the Democratic Republic of Congo; it is located alongside the Semliki River, in the western branch of the Great Rift Valley. In the 1950s, the site was excavated by the Belgian geologist Jean de Heinzelin, who recovered numerous fossil human and animal remains, together with stone and bone artefacts. The assemblage dates mainly to the early part of the African Late Stone Age, from 25,000 to 19,000 years ago. It is housed in the Department of Anthropology and Prehistory at the Royal Belgian Institute of Science, Brussels.

However, the finds also included an upper left first molar that did not appear to be from such a recent period. Known as #Ish25, doubts were cast on its affinities to modern humans as long ago as 1958. A recent study has shown that #Ish25 probably originated from an earlier geological layer than the other fossils and artefacts. Animal remains associated with this layer suggest that it dates to between 2.6 and 2.0 million years ago. These dates make #Ish25 the earliest fossil hominin find from the western branch of the Great Rift Valley (though not the earliest from Central Africa, as much earlier hominins are known from Chad).

Various statistical analyses of the shape and size of #Ish25 suggest closer affinities to hominins from the Late Pliocene/Early Pleistocene than those from the Middle Pleistocene to Recent epochs. The exact hominin species to which the tooth belongs cannot be determined with certainty; Australopithecus africanus, Paranthropus robustus and early Homo are all possibilities.

The western Great Rift Valley underwent episodes of climate change 3.0, 2.6 and 1.8 million years ago; these led to the partial replacement of Congo flora and fauna with those typical of the East Africa; the latter are adapted to more open grassland conditions. The #Ish25 findings suggest that these conditions led to a dispersal of hominins into the region from either East Africa or South Africa.

The study also demonstrates how valuable knowledge can often be gained by applying modern techniques to old anthropological collections.

 Reference:

1. Crevecoeur, I. et al., First Early Hominin from Central Africa (Ishango, Democratic Republic of Congo). PLoS One 9 (1), e84652 (2014).

Çatalhöyük mural might depict volcanic eruption, 6600 BC

A Neolithic-era mural may depict a prehistoric eruption of Mt Hasan in Anatolia, Turkey

Çatalhöyük is a large Neolithic settlement located on the Konya Plain in Central Anatolia. Occupied from 7400 to 6000 BC, the site was 13.5 ha (33 acres) in extent, with a population thought to have ranged from 3,000 to 8,000 – about the size of a typical English market town.

The site first came to the attention of British archaeologist James Mellaart in 1952, but he was unable to investigate further until 1958. Even then his work at another site did not permit him to commence excavations until 1961. Mellaart worked at the site until 1965, and discovered spectacular painted walls, burials and figurines. He believed that Çatalhöyük had been a cult centre of a great mother goddess, a forerunner of the Anatolian earth mother goddess Cybele, who was prominent in Classical times. Despite the global attention attracted by Mellaart’s findings, no further excavations were carried out until 1993. In that year, a team lead by his former student Ian Hodder commenced a program of excavation, site conservation, and research that will continue for many years to come.

Çatalhöyük completely lacked public buildings and despite its size, there were no streets or approaches at ground level. Instead, the rectangular houses directly abutted one another honeycomb style, and were accessed via a trapdoor in the roof. The only way of getting about was to walk over the flat roofs of neighbouring houses. Ladders were used to get in and out of the houses, and the settlement itself.

Çatalhöyük society was probably fairly egalitarian: there was no chieftain or headman, and decisions were made by a group of elders. The size of the settlement would have necessitated community decisions about drainage, water supply, waste disposal and so on. A degree of collective organisation must also have been involved in such matters as hunting and allocation of land for farming and herding.

The interior walls of the houses were richly decorated with paintings and moulded reliefs, mainly of wild animals including leopards, bulls, deer, goats and vultures. Reliefs of leopards frequently feature a pair of animals standing head to head. Some paintings depict human figures, including one apparently wearing a leopard skin; others depict hunting scenes. In many houses, the skulls and horns of bulls and other animals were plastered and set into the walls or placed on pillars. In 1962, Mellaart discovered a mural which he subsequently described as the world’s oldest map. Approximately 3 metres (9 ft. 10 in) wide, the mural was painted on the northern and eastern walls of a room described as Shrine 14. It was later removed from the excavation site and is currently on display at the Museum of Anatolian Civilisations in Ankara. It dates to between 6790 and 6430 BC.



The lower register of the mural contains around 80 square patterns tightly arranged like cells in a honeycomb, which has been interpreted as a bird’s eye view of the settlement. The upper register depicts an object that its discoverers identified as a portrayal of a twin-peaked mountain. It closely resembles the now-dormant volcano Mt Hasan, located 130 km (80 miles) northeast of Çatalhöyük. The ‘map’ interpretation of the mural proposes that eruptions of Mt Hasan might have been of significance to the inhabitants of Çatalhöyük because they collected obsidian from its vicinity (although not from the volcano itself). Another possibility is that they witnessed a violent eruption and that the volcano subsequently became associated with a religious cult.

A problem for this view has been a lack of any independent evidence that Mt Hasan was active during the period that Çatalhöyük was occupied. An alternative interpretation of the mural is that it is a representation of a leopard skin. The leopard appears to have been important to the inhabitants of Çatalhöyük, and as noted above, is a prominent motif in their artwork.

In 2013, a team of geologists led by Axel Schmitt from UCLA collected and dated samples from the summit and flanks of Mt Hasan using (U-Th)/He zircon geochronology, a radiometric dating technique widely used for dating volcanic material. They established that the volcano erupted at some time between 7600 and 6320 BC – corresponding fairly closely to the time that Çatalhöyük was occupied, and strengthening the case that this is what the mural depicts.

The team also concluded that Mt Hasan is not extinct, and that future eruptions are possible.

 References:

1. Hodder, I., Çatalhöyük the Leopard's Tale (Thames & Hudson, London, 2006).

2. Schmitt, A. et al., Identifying the Volcanic Eruption Depicted in a Neolithic Painting at Çatalhöyük, Central Anatolia, Turkey. PLoS One 9 (1), e84711 (2014).

Study suggests Neanderthals could speak like modern humans

Kebara 2 hyoid bone suggests similar linguistic abilities.

Whether or not Neanderthals could speak like modern humans has been the subject of a long-running debate. For a long time, it was believed that they did not. Based on the analysis of Neanderthal specimen from La Chapelle-aux-Saints, France, it was claimed that the Neanderthal larynx was positioned high in the throat, like a chimpanzee (or a modern human baby), making it impossible for Neanderthals to produce the modern range of vocalisations (d’Errico, et al., 2003).

However, the hyoid bone of Kebara 2, a fossil Neanderthal from Mt. Carmel in Israel, has provided new evidence. The hyoid is a small U-shaped bone that lies between the root of the tongue and the larynx, anchoring the muscles required for speech. The Kebara 2 hyoid is within the modern range in form. Furthermore, by analysis of patterns of muscle attachment, researchers were able to show that the placement of the larynx was similar to that of a modern human, low in the throat (Arensburg, et al., 1989; Arensburg, et al., 1990).

3d modelling work has supported these conclusions. Data from a number of Neanderthal skulls was used to reconstruct the vocal tract. The estimated hyoid position fell within the modern range and acoustic analysis shows that Neanderthals were able to make the quantal vowel sounds (/a/, /i/ and /u/) that are present in all modern human languages. The Neanderthal /i/ and /u/ sounds are within the modern range; /a/ falls just outside (Barney, et al., 2012).

The latest study follows on from this work and used X-ray microtomography to map the internal structure of the Kebara 2 hyoid. It was found that this, too, was within the modern range. Mechanical modelling showed that the micro-biomechanical performance of the hyoid under the loadings it would experience when in use was very similar to that of modern humans. Thus the Kebara 2 hyoid doesn’t just resemble a modern hyoid both externally and internally, it was used in a very similar way (D’Anastasio, et al., 2013).
These results show that from a biomechanical point of view, Neanderthals were fully capable of modern speech. It leaves unresolved the issue as to whether or not they possessed the cognitive abilities, but there is a mounting body of evidence to suggest that their subsistence strategies and other behaviours were far more advanced than previously believed.

References:

1. d’Errico, F. et al., Archaeological Evidence for the Emergence of Language, Symbolism, and Music — An Alternative Multidisciplinary Perspective. Journal of World Prehistory 17 (1), 1-70 (2003).

2. Arensburg, B., Tillier, A., Vandermeersch, B., Duday, H. & Rak, Y., A middle Palaeolithic human hyoid bone. Nature 338, 758–760 (1989).

3. Arensburg, B., Schepartz, L., Tillier, A., Vandermeersch, B. & Rak, Y., A reappraisal of the anatomical basis for speech in Middle Palaeolithic hominids. American Journal of Physical Anthropology 83 (2), 137-146 (1990).

4. Barney, A., Martelli, S., Serrurier, A. & Steele, J., Articulatory capacity of Neanderthals, a very recent and human-like fossil hominin. Philosophical Transactions of the Royal Society B 367, 88–102 (2012).

5. D’Anastasio, R. et al., Micro-Biomechanics of the Kebara 2 Hyoid and Its Implications for Speech in Neanderthals. PLoS One 8 (12) (2013).

530,000 years old Spanish hominins were closely related to Denisovans

Mystery of Sima de los Huesos ‘proto-Neanderthal’ mitochondrial genome.

Sima de los Huesos – ‘the Pit of Bones’ –  is a small muddy chamber lying at the bottom of a 13 m (43 ft.) chimney, lying deep within the Cueva Mayor system of caves in the Sierra de Atapuerca of northern Spain. Human remains dating to the Middle Pleistocene were first discovered there in 1976, and systematic excavation has been in progress since 1984. Investigation of the cramped site has proved to be long and difficult – it is located more than 500 m (⅓ mile) from the mouth of the Cueva Mayor and is hard to access, necessitating at times crawling on the stomach. To date, over 2,000 fragmentary hominin fossils have been recovered, including three skulls. In total, the remains are thought to represent at least 32 individuals of both sexes. Many of the remains are of adolescents and young adults, though, the pattern of mortality was probably quite normal for the time, and a similar peak in adolescence has been found at a site at Krapina in Croatia. There is no evidence for violence and the deaths could simply be the result of hunting accidents and childbirth complications. Hunting accidents were probably not uncommon among inexperienced young hunters and women likely fell pregnant soon after commencing menstruation (Pettitt, 2005).
Uranium-series dating suggests that the remains are least 530,000 years old (Bischoff, et al., 2007), and display a mixture of Homo heidelbergensis and Neanderthal features. For this reason, the  Sima de los Huesos hominins are often described as ‘proto-Neanderthal’ (Klein, 2009), although it has also been argued that they were a species distinct from both Neanderthals and Homo heidelbergensis rather than an intermediate between the two (Tattersall, 2002).

In a newly-published study, researchers at the Max Planck Institute for Evolutionary Anthropology have reported the sequencing of the almost-complete mitochondrial genome of one of the Sima de los Huesos hominins. The mitochondrial DNA was extracted from a thigh bone. An estimated age of 400,000 years was obtained by comparison with other, younger ancient DNA sequences dated by direct means. This is rather more recent than the uranium series dates for the site, but still by far the oldest hominin DNA ever recovered. The previous record-holder was no more than 100,000 years old.

Given the geographical location of the Sima de los Huesos and the apparent affinities of the hominins to Neanderthals, it was expected that the material would show affinity to genetic sequences obtained from later Neanderthal remains. Instead, it more closely resembled ancestral Denisovan mitochondrial DNA (Meyer, et al., 2013).

The Denisovan genome, first identified Denisova Cave in the Altai Mountains of southern Siberia, has been found in the modern populations of New Guinea and Island Southeast Asia, implying that the Denisovan range had once extended from the deciduous forests of Siberia to the tropics. This is a wider ecological and geographic region than any other hominin species, with the exception of modern humans (Reich, et al., 2011); but could their range have extended all the way to Europe?

It is likelier that the Sima de los Huesos hominins were the common ancestors of both the Neanderthals and the Denisovans. Mitochondrial lineages originally present in both lineages subsequently disappeared from the Neanderthals, but persisted in the Denisovans. They could have been lost from the Neanderthal line as a result of a population bottleneck of the type known to have affected later Neanderthal populations (Dalén, et al., 2012).

References:

1. Pettitt, P., in The Human Past, edited by Scarre, C. (Thames & Hudson, London, 2005), pp. 124-173.

2. Bischoff, J. et al., High-resolution U-series dates from the Sima de los Huesos hominids yields 600 +/-66 kyrs: implications for the evolution of the early Neanderthal lineage. Journal of Archaeological Science 34, 763-770 (2007).

3. Klein, R., The Human Career, 3rd ed. (University of Chicago Press, Chicago, IL, 2009).

4. Tattersall, I., in The Speciation of Modern Homo sapiens, edited by Crow, T. (Oxford University Press, Oxford, 2002), pp. 49-59.

5. Meyer, M. et al., A mitochondrial genome sequence of a hominin from Sima de los Huesos. Nature (Published online) (2013).

6. Reich, D. et al., Denisova Admixture and the First Modern Human Dispersals into Southeast Asia and Oceania. American Journal of Human Genetics 89, 1-13 (2011).

7. Dalén, L. et al., Partial genetic turnover in neandertals: continuity in the east and population replacement in the west. Molecular Biology and Evolution 29 (8), 1893-1897 (2012).

The Denisovans

In 2008, a distal manual phalanx of from a hominin little finger was recovered from Denisova Cave in the Altai Mountains of southern Siberia. The cave is named for a hermit called Dionisij (Denis) who is supposed to have lived there in eighteenth century, but if this is true he was only the latest in a long line of inhabitants. In April 2010, it was reported that the phalanx had belonged to a hitherto-unknown human species (Krause, et al., 2010).

The small bone was dated by stratigraphic methods and found to be in the region of 30,000 to 48,000 years old. It was believed to have belonged to a child aged between five and seven years old, but other than that no morphological classification could be made. Due to the cool, dry climate, it proved to be possible to extract DNA from the bone, isolate mtDNA fragments, and sequence the entire mitochondrial genome. As we inherit our mtDNA solely from our mothers, this led to the find being dubbed X Woman, despite being a juvenile of unknown gender.

At the time in question, Neanderthals, identified as such by their mtDNA, were living less than 100 km (60 miles) away. The presence of an Upper Palaeolithic industry at Siberian sites such as Kara-Bom and Denisova itself has been taken as evidence for the appearance of modern humans in the Altai before 40,000 years ago. The expectation, therefore, was that the mitochondrial DNA from the bone would match that of either Neanderthals or modern humans, but neither turned out to be the case. Instead, sequencing revealed that X Woman had last shared a common ancestor with Neanderthals and modern humans about a million years ago.

X Woman clearly wasn’t a Neanderthal or a modern human, but what was she (if indeed she was a ‘she’)? One possibility was Homo heidelbergensis, the presumptive common ancestor of the Neanderthals and modern humans, but this species probably appeared no earlier than 600,000 years ago, and was too recent to be associated with X Woman’s ancestors. On the other hand, one million years ago was too recent for X Woman to be a late-surviving descendant of the first wave of Homo erectus to reach Southeast Asia and China.

Towards the end of 2010, it was reported that X Woman’s nuclear genome had been sequenced (Reich, et al., 2010). It turned out that X-Woman lacked a Y-chromosome and therefore was indeed female. The discovery of an upper molar tooth from a young adult was also reported. The sequencing of mtDNA from the tooth confirmed that it belonged to a different individual to the phalanx. For this reason, the term ‘X-Woman’ was dropped in favour of ‘Denisovan’.

The nuclear data allowed more detailed estimates to be made regarding the relatedness of Denisovans, Neanderthals and modern humans. It was found that the Denisovans diverged from Neanderthals 640,000 years ago, and from present-day Africans 804,000 years ago. This meant that the Denisovans were more closely related to the Neanderthals than to modern humans, and may thus be considered a sister group of the former. The most remarkable finding was that 4.8 percent of the nuclear genome of present-day New Guineans derives from Denisovans, greater than the Neanderthal contribution of 2.5 percent (Reich, et al., 2010). The implication was that the Denisovan range had once extended from the deciduous forests of Siberia to the tropics. This is a wider ecological and geographic region than any other hominin with the exception of modern humans (Reich, et al., 2011). Overall, the data was consistent with a scenario in which modern humans, on leaving Africa, interbred with Neanderthals and then, at some subsequent point, the ancestors of present-day New Guineans interbred with Denisovans.

Follow-up studies confirmed the presence of Denisovan genetic material in some other modern populations of island Southeast Asia, and also in Aboriginal Australians, Fijians and Polynesians. Significantly, though, it was absent from mainland populations. The only logical explanation is that the present-day population of Mainland Southeast Asia are descended from a second group of migrants that arrived after the Denisovans had become extinct (Reich, et al., 2011; Skoglund & Jakobsson, 2011; Meyer, et al., 2012).

Interbreeding with Denisovans might have boosted the immune systems of some modern populations. The human leucocyte antigen (HLA) helps the immune system to recognise and combat pathogens. There are three genes known as HLA-A, HLA-B and HLA-C, and it believed that a number of variants of these genes are of Denisovan origin. These variants could have conferred immunity to pathogens to which the incoming modern population had not been previously exposed, and given a survival to those acquiring them from the Denisovans. It is possible that the modern immune system has thus been shaped by ‘importing’ advantageous genes from archaic populations throughout Eurasia (Abi-Rached, et al., 2011).

It has been suggested, on the basis of allele comparison, that the Denisovans were dark-skinned, with brown eyes and hair (Meyer, et al., 2012). Other than that, and beyond their genetic impact on modern populations, we still know very little about them. The Middle Pleistocene fossil record of Southeast and East Asia is very sparse and the Denisova tooth, probably a third or possibly second left upper molar, fails to support a connection with any of the few remains that have been found. The tooth is fairly large, lying within the size range of Homo erectus and Homo habilis. It is above the size range typical for Neanderthals, early modern humans, and the very few third upper molars that have been recovered from other late archaic hominins in the region. The tooth shares no derived morphological features with Neanderthals or modern humans, hinting at the distinctiveness of the Denisovans (Reich, et al., 2010). On the other hand, the report failed to note that some early modern human teeth are also very large, such as those associated with the 35,000-year-old lower jawbone from Peştera cu Oase in Romania (Trinkaus, et al., 2003; Trinkaus, et al., 2003). Size alone probably does not tell us very much (Hawks, 2010).

Recently, it has been suggested that the Denisovans interbred with yet another archaic human species. Given that the Denisovans and Neanderthals diverged from one another after they diverged from modern humans, one would expect the two species to be equally genetically distinct from our own species. However, this is not the case; the Denisovans are more genetically distinct than the Neanderthals. It turns out that scattered fragments amounting to around one percent of their genome is much older than the rest of it. This is best explained by the Denisovans interbreeding with an as yet unidentified human species, possibly Homo heidelbergensis or Homo erectus. We do not yet have genetic material from either species, so this cannot be confirmed (Marshall, 2013).

At all events, it is now clear that the view of modern humans entirely replacing archaic populations is not correct, either in or out of Africa. There is certainly an element of truth to the multiregional model. It is, however, only an element. The range of morphological variation between modern and archaic humans is greater than that in any existing primate species. We should not think of Denisovans and Neanderthals as simply variant forms of Homo sapiens (Stringer, 2012).

References:

Abi-Rached, L. et al., 2011. The Shaping of Modern Human Immune Systems by Multiregional Admixture with Archaic Humans. Science, 25 August.

Hawks, J., 2010. The Denisova genome FAQ. [Online]
Available at: http://johnhawks.net/weblog/reviews/neandertals/neandertal_dna/denisova-nuclear-genome-reich-2010.html
[Accessed 14 November 2011].

Krause, J. et al., 2010. The complete mitochondrial DNA genome of an unknown hominin from southern Siberia. Nature, 8 April, Volume 464, pp. 894-897.

Marshall, M., 2013. Mystery human species emerges from Denisovan genome. [Online]
Available at: http://www.newscientist.com/article/dn24603-mystery-human-species-emerges-from-denisovan-genome.html#.Uo5FQMTk-m5
[Accessed 21 November 2013].

Meyer, M. et al., 2012. A High-Coverage Genome Sequence from an Archaic Denisovan Individual. Science, 30 August.

Reich, D. et al., 2010. Genetic history of an archaic hominin group from Denisova Cave in Siberia. Nature, 23/30 December, Volume 468, pp. 1053-1060.

Reich, D. et al., 2011. Denisova Admixture and the First Modern Human Dispersals into Southeast Asia and Oceania. The American Journal of Human Genetics, 7 October, Volume 89, pp. 1-13.

Skoglund, P. & Jakobsson, M., 2011. Archaic human ancestry in East Asia. PNAS.

Stringer, C., 2012. What makes a modern human. Nature, 3 May, Volume 485, pp. 33-35.

Trinkaus, E. et al., 2003. Early modern human cranial remains from the Pestera cu Oase, Romania. Journal of Human Evolution, Volume 45, p. 245–253.

Trinkaus, E. et al., 2003. An early modern human from Peştera cu Oase, Romania. PNAS, 30 September, 100(20), p. 11231–11236.

Projectile weapons invented almost 280,000 years ago, by pre-modern humans

Study suggests Ethiopian Rift stone points were used as hafted javelin tips.

The invention of projectile weaponry was clearly an important advance for early humans, enabling large mammals or enemies to be killed or wounded at a distance, without the dangers of a confrontation at close quarters.

The earliest humans probably hunted to an extent, but unequivocal evidence for the hunting of large mammals does not appear in the archaeological record until the Middle Pleistocene. In 1995, four wooden spears were discovered at an open cast mine near the town of Schöningen in Germany. The 400,000-year-old weapons were found with the carcasses of the horses they had been used to kill: the earliest-known association of hunting weapon with quarry. Each spear was over 2 m (6 ft. 6 in.) long, sharpened at both ends, and scraped smooth with stone tools (Thieme, 1997). However, these were unlikely to have been projectile weapons. They are closer in thickness to ethnographically-recorded thrusting spears rather than throwing spears, and if thrown would have had a killing radius of less than 8 m (26 ft.) (Shea, 2006).

Even earlier are the 500,000-year-old stone points from the site of Kathu Pan 1 (KP 1) in South Africa. Some exhibit fractures to their ends, bases and edges that are consistent with a short-ranged weapon striking a target – but not with use for cutting or scraping. The points are shaped near the base in a way that suggests that they were hafted to wooden spears. Experiments with replicas of the KP 1 points, made from similar raw materials, suggest that they made effective spear tips. This makes them the earliest-known multi-component tools; however, they were thrusting spears rather than projectile weapons (Wilkins, et al., 2012).

Throwing spears or javelins were once thought to be a technology unique to modern humans. However, a newly-published study suggests that they predate the emergence of Homo sapiens by 80,000 years. The Gademotta Formation is an archaeological site located on the flanks of an ancient volcanic caldera in the Ethiopian Rift. Investigations since 2010 have yielded over two hundred intact or fragmentary stone points, nearly all of which made from locally-available obsidian. Obsidian is a naturally-occurring volcanic glass that is well-suited to the production of implements with a sharp cutting edge. Argon-argon dating suggests that the oldest of the artefacts are 279,000 years old. Many of the points were found to bear fracture patterns on their tips consistent with impact damage arising from their use as hafted javelin tips, rather than as thrusting weapons (Sahle, et al., 2013).

The pre-modern humans living in Africa at this time are commonly referred to as Homo heidelbergensis. It is commonly supposed that they lacked the cognitive abilities of modern humans (Klein & Edgar, 2002), but the emerging view is that the sophistication of Middle Pleistocene humans has been severely underestimated. The Gademotta projectile tips are an important piece of evidence in this new picture.

References:

1. Thieme, H., Lower Paleolithic hunting spears from Germany. Nature 385, 807-810 (1997).

2. Shea, J., The origins of lithic projectile point technology: evidence from Africa, the Levant, and Europe. Journal of Archaeological Science 33, 823-846 (2006).

3. Wilkins, J., Schoville, B., Brown, K. & Chazan, M., Evidence for Early Hafted Hunting Technology. Science 338, 942-946 (2012).

4. Sahle, Y. et al., Earliest Stone-Tipped Projectiles from the Ethiopian Rift Date to.279,000 Years Ago. PLoS One 8 (11) (2013).

5. Klein, R. & Edgar, B., The Dawn of Human Culture (John Wiley & Sons, Inc., New York, NY, 2002).

Mesolithic hunter-gatherers persisted in Central Europe for 2,000 years after arrival of farmers

Study indicates that foragers maintained way of life alongside farming communities.

Farming spread across Europe from Southwest Asia between 6500 and 4000 BC, but interactions between the indigenous Mesolithic hunter-gatherers and incoming Neolithic farmers are poorly understood. The general view is that hunter-gathering disappeared soon after the arrival of agriculture, but whether the hunter-gatherers took up farming themselves or simply died out remains uncertain.

In order to investigate relationships between foragers and farmers, researchers examined Mesolithic and Neolithic samples from Blätterhöhle, a cave site near Hagen in North Rhine-Westphalia, Germany (Bollongino, et al., 2013). The cave contained the remains of around 450 Neolithic and Mesolithic individuals. It is likely that it was a burial ground, and that these individuals were deposited there deliberately. Radiocarbon dating has revealed two phases of occupation: a Mesolithic occupation from 9210 to 8340 BC, and a Late Neolithic occupation from 3986 to 2918 BC.

Stable isotope analysis and ancient mitochondrial DNA extraction was carried out on the bones and teeth of 29 individuals. Isotopic ratios of sulphur, nitrogen and carbon in human remains can provide an insight into the diet of an individual while they were alive. Mitochondrial DNA can trace maternal ancestry.

Of the 29 individuals sampled, 25 yielded usable mitochondrial DNA; five from the Mesolithic occupation and 20 from the Late Neolithic occupation. The five Mesolithic-era individuals all belonged to mitochondrial haplogroup U, in common with other pre-Neolithic hunter-gatherers of central, eastern and northern Europe. More unexpectedly, twelve of the Neolithic-era individuals also belonged to haplogroup U. This haplogroup is rare among Late Neolithic farmers, and suggests a surprising persistence of Mesolithic maternal ancestry. The remaining eight individuals belonged to typical Neolithic haplogroups.

Stable isotope analysis indicated the existence of three distinct groups. The first, comprising the Mesolithic-era individuals, subsisted on a diet of wild foods typical of that found at other inland Mesolithic sites. The second group comprised Late Neolithic individuals with a diet of domesticated animals typical of German Neolithic sites. The third group was also from the Late Neolithic, but diet was unusual: low in plant and animal protein and high in freshwater fish.

The members of this third group all belonged to mitochondrial haplogroup U, whereas members of the contemporary second group were a mixture of Mesolithic and Neolithic haplogroups. Thus it appears that a group of fisher-foragers were living alongside a group of farmers in the fourth millennium BC, which is around 2,000 years after agriculture reached central Europe. That both groups used the Blätterhöhle cave site at the same time indicates that they were near-neighbours.

Ethnographic data shows that such communities do live side by side, commonly exchanging food; for example cereals for fish. While forager women do marry into farming communities, the reverse is very rare as women from farming communities regard it as marrying down. The mitochondrial results are consistent with the ethnographic picture: no Neolithic haplogroups were found among the fisher-foragers; but the Mesolithic haplogroup U was present among the farmers.

It is unclear just how prevalent such forager communities were in Late Neolithic Europe, but the Blätterhöhle results are the strongest indication yet that such genetically-distinct communities persisted long after the arrival of farming. The ultimate fate of these communities remains uncertain. The authors of the study suggest that some groups may have eventually changed over to farming, although it has been suggested that incoming farmers would rapidly appropriate all the prime farmland, making such a switch problematic (Bellwood, 2005).

References:

1. Bollongino, R. et al., 2000 Years of Parallel Societies in Stone Age Central Europe. Science 342, 479-481 (2013).

2. Bellwood, P., First Farmers (Blackwell Publishing, Oxford, 2005).

First came the temple, then the city

What was the purpose of 11,000 year old monument at Göbekli Tepe?

Located on a limestone ridge 15 km (9 miles) from the town of Şanlıurfa in southeastern Turkey is a site unlike any other known in the early Neolithic world of Southwest Asia. Göbekli Tepe is thought to be the world’s oldest temple. It comprises a series of stone circles that draw superficial comparison to Stonehenge, but it predates the well-known Salisbury Plain monument by seven millennia.

Göbekli Tepe was noted as far back as the early 1960s, but was largely ignored for thirty years. Not until 1994 was it visited by German archaeologist Klaus Schmidt, who believed that the site was Neolithic. He began excavating there the following year, and work has been ongoing ever since.

At the lowest level of the site, Layer III, Schmidt discovered series of semi-submerged circular or oval enclosures. Each comprises a dry-stone wall, into which up to twelve T-shaped limestone pillars are set, often joined to one another by stone benches. At the centre of each enclosure are two more pillars, which tend to be larger than the surrounding ones. The pillars range in height from 3 to 5 m (10 to 16 ft.) and weigh up to 10 tonnes. They were quarried from limestone plateaus close to the site, where a number of incomplete pillars remain in situ. One weighs over 50 tonnes, larger than any of the finished pillars so far excavated. Currently, four enclosures, designated A to D, are undergoing excavation, but geomagnetic surveys suggest that least twenty exist. Many of the pillars are carved with bas-reliefs of animals, including snakes, wild boar, foxes, lions, aurochs, wild sheep, gazelle, onager, birds, various insects, spiders, and scorpions. Where sexual characteristics are present, they are always male. The images are large, often life-size, and semi-naturalistic in style. Some pillars exhibit pairs of human arms and hands, suggesting that they represent stylised anthropomorphic beings. However, it is unclear as to whether they represent gods, shamans, ancestors, or even demons. There are also a number of mysterious abstract symbols that have been interpreted as pictograms (Schmidt, 1995; Schmidt, 1998; Schmidt, 2000; Schmidt, 2003; Peters & Schmidt, 2004).

Pictograms are graphic symbols used to convey meaning, often by pictorial resemblance to a physical object. They are widely used in present-day road and other public signage to denote traffic lights, pedestrian crossings, speed cameras, etc. If the Göbekli Tepe symbols were indeed pictograms, then the origins of writing may extend back into the early Neolithic, thousands of years before the appearance of writing systems such as cuneiform and hieroglyphic script.

No traces of houses have been found and there is little doubt that Göbekli Tepe was a ritual centre, possibly the first of its kind anywhere in the world (Schmidt, 1998). Unlike Stonehenge, the people who built Göbekli Tepe lacked a mixed farming economy. This overturned the conventional wisdom that such major projects could only be realised by fully-established farming communities. “First came the temple, then the city”, as Schmidt put it. How are we to interpret this temple?

One possibility is that the animals depicted in the various enclosures are totemic. It could be that the site was frequented by a number of groups, each of which identified itself with a different animal or animals and travelled to the site to perform rituals in its own particular enclosure (Peters & Schmidt, 2004). Another possibility is that Göbekli Tepe was associated with shamanistic practices (Lewis-Williams & Pearce, 2005).

A project on the scale of Göbekli Tepe would have required a large number of labourers and craftsmen. Coordinating the activities of all these people, to say nothing of providing them all with food and shelter, would have been a major undertaking. It should also be remembered that unlike the builders of Stonehenge, the Göbekli Tepe people were still not yet full agriculturalists. Such an undertaking was almost certainly beyond the capabilities of a few shamans and their communities. Instead, it seems likely that the monument was constructed by a hierarchical, stratified society, with powerful rulers. The shamans might have had more in common with priests (Peters & Schmidt, 2004). The link between rulers and religion, so prevalent in later times, might have already started to take shape.

The totemic and shamanistic explanations are not necessarily mutually exclusive, and if the totemic view is correct, then it possible that animals depicted in each enclosure could provide clues as to the origins of particular groups. For example, wild boar depictions predominate in Enclosure C. This suggests a group originating from the north, where pigs account for up to 40 percent of the animal remains found at PPNA sites. Combinations of wild boar with aurochs and cranes, as seen in Enclosure D, suggest an ecotone of steppe and river valley, such as along most water courses in the Euphrates and Tigris drainage regions (Peters & Schmidt, 2004).

Eventually, the enclosures at Göbekli Tepe complex were filled in and buried with debris. Animal remains and stone artefacts mixed in with the soil suggest that the filling material came from a typical late PPNA settlement refuse dump. The settlement has not been found, but the amount of debris involved suggests that it was not far away. Subsequently, a far less impressive complex was constructed over the first, comprising rectangular pits with smaller pillars, averaging about 1.5 m (5 ft.) (Peters & Schmidt, 2004).

Establishing a chronology for the site is difficult. Plant remains from the settlement debris have been dated to around 9000 BC (Kromer & Schmidt, 1998), but this does not tell us when the site was first occupied. Assuming that the debris accumulated while the Layer III site was in use, the first occupation of the site would be no later than this date. Based on dates for soil overlaying the filling debris, the Layer III complex was probably buried around 8000 BC (Peters & Schmidt, 2004). Dates for carbonates formed on the stone walls as a result of their burial suggest it could have been no later than 7700 BC (Pustovoytov, 2002).

Just why the Layer III complex was buried and the Layer II complex built over it is not known. A possible clue comes from the site of Nevali Çori, 30 km (18 miles) away. Unfortunately, this site was submerged following the construction of the Atatürk Dam. Prior to flooding, the site was excavated between 1983 and 1991 by Harold Hauptmann from the University of Heidelberg. The site was first occupied around 8500 BC, at the start of the PPNB, and occupation spanned three phases before final abandonment around 7600 BC ( Ex Oriente eV Scientific Society, 2011). It comprised some 29 rectangular multi-roomed houses and a ‘cult building’ – marking a shift from circular houses to the rectangular constructions that have largely characterised human dwellings ever since. The cult building dates to the site’s second and third phases. It was approximately square, measuring 13.9 by 13.5 m (45 ft. 7 in. by 45 ft. 4 in.), and was cut about 3 m (10 ft.) into the slope behind it. Access was via two downward steps. A stone bench ran all the way around the interior, broken by pillars similar to those at Göbekli Tepe and again surrounding a central pair, although they resembled the Hebrew letter ד (daleth) rather than the letter T (Peters & Schmidt, 2004; Lewis-Williams & Pearce, 2005). There is clearly a connection between the two sites, and possibly the shift to rectangular architecture is why Göbekli Tepe was filled in and rebuilt along rectangular lines.

References:

1. Schmidt, K., Investigations in the early Meospotamian Neolithic: Göbekli Tepe and Gürcütepe. Neo-Lithics (2/95), 9-10 (1995).

2. Schmidt, K., Beyond Daily Bread: Evidence of Early Neolithic Ritual from Göbekli Tepe. Neo-Lithics (2/98), 1-5 (1998).

3. Schmidt, K., Göbekli Tepe, Southeastern Turkey A Preliminary Report on the 1995-1999 Excavations. Paléorient 26 (1), 45-54 (2000).

4. Schmidt, K., The 2003 Campaign at Göbekli Tepe (Southeastern Turkey). Neo-Lithics (2/03), 3-8 (2003).

5. Peters, J. & Schmidt, K., Animals in the symbolic world of Pre-Pottery Neolithic Göbekli Tepe, south-eastern Turkey: a preliminary assessment. Anthropozoologica 39 (1), 179-218 (2004).

6. Lewis-Williams, D. & Pearce, D., Inside the Neolithic Mind (Thames & Hudson, London, 2005).

7. Kromer, B. & Schmidt, K., Two Radiocarbon Dates from Göbekli Tepe, South Eastern Turkey. Neo-Lithics (3/98), 8-9 (1998).

8. Pustovoytov, K., 14 C Dating of Pedogenic Carbonate Coatings on Wall Stones at Göbekli Tepe (Southeastern Turkey). Neo-Lithics (2/02), 3-4 (2002).

9. Ex Oriente eV Scientific Society, PPND - the platform for Neolithic Radiocarbon Dates, Available at http://www.exoriente.org/associated_projects/ppnd.php (2011).

Did Neanderthals invent tool used by present-day leather-workers?

Specialist bone tool predates arrival of Homo sapiens in Europe.

Two sites in the Dordogne Valley in southern France have yielded four nearly identical deer rib fragments with smoothed edges. These have been interpreted as being a type of tool known as a lissoir (French ‘to make smooth’) used for preparing animal hides. The lissoir is used by present-day leather-workers to make hides softer, tougher and more waterproof. No other known artefact from the Middle or Upper Palaeolithic could be used for such a task. To manufacture such an implement, it is necessary to polish and grind rib fragments to a predetermined size and shape.

A date of 51,500 years old has been obtained for one of the artefacts using optically stimulated luminescence, making these tools the earliest-known specialised bone tools in Europe. Crucially, this date is around 5,000 years before modern humans reached Europe, implying that the tools were manufactured by Neanderthals. This is further proof of Neanderthal sophistication: they clearly knew how to exploit the specific properties of bone both for shaping and for use as a tool.

Even if there were some long-range interactions between Neanderthals and modern humans at this early stage, there is no evidence that the latter used such tools until much later. The Dordogne implements are therefore likely to be of independent Neanderthal invention.

Furthermore, it is entirely possible that modern humans did not reinvent the lissoir but learned about it from the Neanderthals. When present-day leather-workers use such a tool, they could actually be using a Neanderthal invention.

Reference:

1. Soressi, M. et al., Neandertals made the first specialized bone tools in Europe. PNAS 110 (35), 14186-14190 (2013).