Movius Line explained?

500,000-year-old shell cutting tool could explain Acheulean hand-axe puzzle

The teardrop shaped Acheulean hand-axe is without doubt the signature artefact of the Lower Palaeolithic, remaining in use for nearly one and a half million years. The tools first came into use about 1.75 million years ago and persisted until around 250,000 years ago. While chiefly associated with Homo erectus, they remained in use into the time of the larger-brained Homo heidelbergensis.

What has long been a puzzle is that while the hand-axes are ubiquitous in Africa, Europe and Southwest Asia, they are very rare further east. The boundary between the two regions is known as the Movius Line, after the American archaeologist Hallam Movius who first noted the discontinuity in 1948. The Movius Line has largely stood the test of time: the occasional Acheulean-like artefacts that have been found in China and South Korea are probably due to an eastwards migration of later hominins about 250,000 years ago (Cameron & Groves, 2004). By this time, hand-axes had been abandoned in the West (Klein, 2005).

The simplest explanation is that the ancestors of Homo erectus living east of the Movius Line had already left Africa by the time the hand-axes were invented (Swisher, et al., 1994). Another possibility is that not every hominin group in Africa adopted Acheulean technology, and that the original migrants were among those lacking it (Lepre, et al., 2011). Both possibilities suppose that firstly, the hand-axes were only invented once (or were not re-invented by groups that had left Africa); and that secondly, after the initial colonisation of Southeast Asia and China, the migrants there had no significant contact with the Acheulean-using peoples living elsewhere. Another possibilities is that the population sizes at the extremities of the migration were too low to keep the skills necessary for hand-axe production alive from one generation to the next (Lycett & von Cramon-Taubadel, 2008). None of these explanations are very compelling, because it is now known that prepared-core techniques were independently invented in Africa and Eurasia (Adler, et al., 2014), and it therefore seems unlikely that the simpler Acheulean technology arose only once.

A more likely explanation is that migrants passed through a region lacking suitable raw materials to make the hand-axes and were forced to look to alternatives for tool-making. One suggestion is they switched to bamboo and either forgot how to make hand-axes or were happy to stick with bamboo even when suitable stone was available (Klein, 2005). It is also possible that they switched to bamboo because it is readily available and an excellent tool-making material in its own right (Cameron & Groves, 2004; Roberts, 2009; Lewin & Foley, 2004).

It has long been claimed that the theory cannot be proved because bamboo implements from such a long time ago are extremely unlikely to have survived – but there are other alternatives to stone that can survive for hundreds of thousands of years. The recently-discovered shell cutting tool from Trinil, Java, is around 500,000 years old, and it was found in a region where suitable stone is scarce (Joordens, et al., 2014). Although it is far more recent than the first eastwards migration of Homo erectus, it demonstrates that the species was capable of utilising alternative raw materials for tool-making where necessary. It therefore seems likely that the Movius Line represents a shift to the use of organic materials for tool-making when stone suitable for hand-axe manufacture was unavailable.

References:

1. Cameron, D. & Groves, C., Bones, Stones and Molecules: “Out of Africa” and Human Origins (Elsevier Academic Press, London, 2004).
2. Klein, R., in The Human Past, edited by Scarre, C. (Thames & Hudson, London, 2005), pp. 84-123.
3. Swisher, C. et al., Age of the earliest known hominids in Java, Indonesia. Science 263, 1118-1121 (1994).
4. Lepre, C. et al., An earlier origin for the Acheulian. Nature 477, 82-85 (2011).
5. Lycett, S. & von Cramon-Taubadel, N., Acheulean variability and hominin dispersals: a model-bound approach. Journal of Archaeological Science 35, 553-562 (2008).
6. Adler, D. et al., Early Levallois technology and the Lower to Middle Paleolithic transition in the Southern Caucasus. Science 345 (6204), 1609-1612 (2014).
7. Roberts, A., The Incredible Human Journey (Bloomsbury, London, 2009).
8. Lewin, R. & Foley, R., Principles of Human Evolution, 2nd ed. (Blackwell Science Ltd, Oxford, 2004).
9. Joordens, J. et al., Homo erectus at Trinil on Java used shells for tool production and engraving. Nature (2014).

Homo erectus engraved abstract patterns on seashells

500,000-year-old shells provide earliest yet evidence for symbolic behaviour

Archaeologists studying freshwater mussel shells excavated in the nineteenth century at Trinil, Java, have discovered geometric patterns carved by Homo erectus 500,000 years ago and unambiguous evidence that one shell had been sharpened and polished for use as a cutting tool. In addition, the number of large adults in the shell assemblage suggests that they were intentionally collected for eating.

The shells were excavated by Dutch anthropologist Eugene Dubois in 1891 during the course of his work in Java, which led to the discovery of Homo erectus. They now form part of the Dubois Collection in the Naturalis Biodiversity Centre in Leiden. Researchers dated sediments within the shells with argon-argon and luminescence methods to obtain an age range of 540,000 to 430,000 years old.

The engraved shell, designated DUB1006-fL, displays a geometric pattern of grooves. The pattern consists of a zigzag line with three sharp turns producing an ‘M’ shape, a set of more superficial parallel lines, and a zigzag with two turns producing an inverted ‘N’ shape. The grooves appear to have been intentionally produced, and comparison with experimentally-made grooves suggest that they were made with a shark tooth.

Previously, the earliest evidence for the carving of abstract patterns was the engraved ochres from Blombos Cave, South Africa, which date from the period 100,000 to 75,000 years ago, and the 60,000 year old engraved ostrich shells from Diepkloof Cave, South Africa. Neanderthals made abstract rock engravings at Gorham’s Cave, Gibraltar, 39,000 years ago. More controversially, it has been suggested that a 230,000 year old pebble found at Berekhat Ram in the Golan Heights is a representation of the female form.

The cutting tool is the earliest-known example of the use of shells for tool-making, and may have been a response to the lack of locally-available material for making stone tools. A similar explanation has been proposed for Neanderthal shell tools from Italy and Greece, but these are only around 110,000 years old.

Finally, seafood is a dietary adaptation was once thought to be exclusive to modern humans, beginning around 165,000 years ago. Subsequently it was discovered that Neanderthals were exploiting seafood on the Malaga coast 150,000 years ago. The Trinil shells show that the use of seafood by humans was a much earlier development.

Overall, the Trinil shells suggest that Homo erectus possessed a far greater behavioural flexibility than previously believed in terms of both tool-making technology and subsistence strategies. The engraved geometric pattern suggest that at least some capacity for symbolic thought was already present in early humans 500,000 years ago.

The findings are published in the journal Nature.

Reference:

1. Joordens, J. et al., Homo erectus at Trinil on Java used shells for tool production and engraving. Nature (2014).