Homo heidelbergensis

Introduction:
Homo heidelbergensis, or “archaic Homo sapiens”, is the name given to the large-brained hominins that appeared in Africa 600,000 years ago and migrated into Europe and possibly Asia. It is conventionally regarded as having given rise to modern humans in Africa and the Neanderthals in Europe.

The type specimen is the Mauer Mandible (Mauer 1), a virtually-complete lower jaw recovered from fluvial beds near the village of Mauer, in south-west Germany. The find was made on 21 October 1907 by a gravel-pit worker named Daniel Hartmann and described the following year by Professor Otto Schoetensack of the University of Heidelberg. The Mauer Mandible has been dated to 500,000 years old.

Until about ten years ago, the rather unsatisfactory term “archaic Homo sapiens” was used to describe any mid-Pleistocene hominin that wasn’t Homo erectus, Homo sapiens, or a Neanderthal. The latter was usually classified as a subspecies of Homo sapiens, i.e. H. s. neanderthalensis, but they are now generally regarded as a separate species. Consequently “archaic Homo sapiens” is itself regarded as a separate species, with the 1907 name Homo heidelbergensis having seniority under the rules of taxonomy.

As Manzi (2004) notes however this is no more than a revision of the old paradigm, with the substitution of a grade “archaic Homo sapiens” with a clade, Homo heidelbergensis, accompanied by the recognition of three distinct species, i.e. H. heidelbergensis, H. neanderthalensis and H. sapiens, with corresponding speciation events between the Middle and Late Pleistocene in Africa and Eurasia.

Whether or not Homo heidelbergensis is a genuine species or simply a grade of “Version 3.0 human" containing several species remains controversial.

Key Fossils:
Kabwe (Broken Hill), Zambia: Skull and several postcranial bones including a femur and a tibia (Broken Hill 1). It was found in an iron and zinc mine in Broken Hill, Northern Rhodesia (now Kabwe, Zambia) in 1921 by a Swiss miner named Tom Zwiglaar. Dating is uncertain, but probably between 700,000 and 400,000 years old. It has a cranial capacity of around 1100cc and was originally described as Homo rhodesiensis.

Lake Ndutu, Tanzania: a 400,000 year old cranium, found in 1973, with an estimated cranial capacity of 1100cc.

Bodo, Middle Awash, Ethiopia: a 670,000-600,000 year old cranium found in 1976 by a survey headed by Jon Kalb. Cranial capacity is 1300cc.

Sima de los Huesos, Atapuerca, Spain: 350,000 year old remains representing 28 individuals, including three nearly complete skulls, SH4 (cranial capacity 1390cc), SH5 (cranial capacity 1125cc) and SH6 (cranial capacity 1220cc).

Petralona, northern Greece: Skull discovered in cave system in 1960, dated 250,000 – 150,000 years old, with a cranial capacity of 1200cc.

La Caune de Arago, Tautavel in southern France: isolated teeth, cranial, mandibular and fragmentary postcranial remains belonging to at least four adults and three children, dated to approximately 450,000 years old. The distorted Arago 21 cranium has an estimated capacity of 1150cc.

Mauer, Germany: the Mauer Mandible, as mentioned above.

Steinheim, Germany: a distorted but nearly complete cranium found in a gravel pit 1933 by Karl Sigrist. It is believed to be 350,000-250,000 years old. The cranial capacity is 1100cc.

Boxgrove, England: a partial tibia discovered in 1994 dated to 423,000-362,000 years old, associated with Acheulian tools.

Swanscombe, England: three skull fragments belonging to the same individual recovered between 1935 and 1955; believed to be 300,000-200,000 years old and popularly known as Swanscombe Man, though now thought to be female. The cranial capacity has been estimated at 1325cc.

Dali, Shaanxi Province, China: a 250,000 year old cranium discovered by Shuntang Liu in 1978, with a cranial capacity of 1120cc.

Jinniu Shan: cranium, vertebrae, ribs, pelvis, patella and limb bones discovered in 1984. The cranial capacity is 1300cc and the remains are believed to be 250,000 years old.

Description:
Manzi (2004) selects the Middle Pliocene fossils from Kabwe, Petralona and Dali fossils as being typical of Homo heidelbergensis. They have a “transitional aspect” between earlier and more recent hominins which include both primitive and derived traits. Primitive or “archaic” features include a heavily-built cranial structure with massive brow ridges; crests in the temporo-occipital region, including erectus-like occipital and angular tori; a low and antero-posteriorly elongated cranial vault; a protruding and large facial skeleton; and the absence of a modern chin. These traits are however reduced in comparison to Homo ergaster/erectus.

The main derived feature is that the general shape of the cranial vault is consistent with increased brain-size. The frontal is less receding than it is in earlier hominins; the parietal profile is more convex along the mid-sagittal plane and less angled in coronal sections; and the occipital squama is more vertical and arched.

The cranial capacity is typically between 1100-1300cc, around 90% of that of modern humans, a considerable increase on that of Homo erectus/ergaster.

Affinities to other hominins:
The view that this species evolved in Africa about 600,000 years ago, then migrated into Europe, and that the two lineages led to respectively Homo sapiens and the Neanderthals, is probably as convincing as any of the alternatives.

Homo antecessor (known only from Spain) has recently been touted as ancestral to Homo heidelbergensis, suggesting that either the latter was a European species that later migrated back into Africa, or that Homo antecessor evolved in Africa.

Another possibility is that African and European Homo heidelbergensis are different species, with the Bodo Cranium an early example of the former. On this view, the African species would take the name originally assigned to the Bodo Cranium, Homo rhodesiensis. However the sudden increase in brain size to 90% of the modern average seen in the fossil record at around 600,000 years ago, after remaining more or less static at 65% during the previous 1.2 million years, does suggest a punctuated event which in turn suggests a single species.

Just about all that can be safely said at the present time is that our understanding is very incomplete!

Technology:
Homo heidelbergensis is associated with the same Acheulian (Mode II) technology as that originated by Homo ergaster 1.65 million years ago; however later Acheulian hand-axes are thinner, more symmetric and more extensively trimmed. Some authorities describe this technology as “Late Acheulian”. It is possible that its appearance is connected with the emergence of Homo heidelbergensis and is a product of this species greater cognitive abilities.

References:

J. M. Bermudez de Castro, J. L. Arsuaga, E. Carbonell, A. Rosas, I. Martınez, M. Mosquera (1997): A Hominid from the Lower Pleistocene of Atapuerca, Spain: Possible Ancestor to Neandertals and Modern Humans, Science Vol. 276 30 May 1997.

Cameron D & Groves C (2004): Bones, Stones and Molecules: “Out of Africa” and Human Origins, Elsevier Academic Press.

Conroy G (1997): “Reconstructing Human Origins: A Modern Synthesis”, W.W. Norton & Co. Inc, New York, NY & London.

Klein, R. (1999): The Human Career (2nd Edition), University of Chicago Press.

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

Lewin, R and Foley, R 2004: Principles of Human Evolution (2nd edition), Blackwell Science Ltd.

Manzi G (2004): Human Evolution at the Matuyama-Brunhes
Boundary, Evolutionary Anthropology 13:11–24 (2004).

Scarre C (2005) (Ed): “The human past”, Thames & Hudson.

Stringer C & Andrews P (2005): “The Complete World of Human Evolution”, Thames & Hudson.

© Christopher Seddon 2009