Herto skulls (Homo sapiens idaltu)

Some new fossils from Herto in Ethiopia, are the oldest known modern human fossils, at 160,000 yrs. The discoverers have assigned them to a new subspecies, Homo sapiens idaltu, and say that they are anatomically and chronologically intermediate between older archaic humans and more recent fully modern humans. Their age and anatomy is cited as strong evidence for the emergence of modern humans from Africa, and against the multiregional theory which argues that modern humans evolved in many places around the world.

Three skulls were found:

BOU-VP-16/1 is an almost complete adult cranium (shown at right). It is large and robust, with a cranial capacity estimated at 1450 cubic centimetres, larger than most modern humans. The skull is long and high in lateral view, and White et al. (2003) list a number of features in which it is near or beyond the limit of modern humans (the occipital angle, mastoid height, palate breadth). Viewed from above, its length exceeds any from a sample of over 3000 modern humans, but one width measurement is below the modern human average. The brow ridge is not prominent and is within the modern human range.
BOU-VP-16/2 consists of portions of another adult cranium which appears to have been even larger than the previous specimen.
BOU-VP-16/5 consists of most of a skullcase from a child, probably about 6 or 7 years of age judging by its teeth.

The conclusion of the authors is that the Herto skulls "sample a population that is on the verge of anatomical modernity but not yet fully modern". They therefore assigned it to a new subspecies idaltu ('elder' in the local Afar language):

"Because the Herto hominids are morphologically just beyond the range of variation seen in AMHS [anatomically modern Homo sapiens], and because they differ from all other known fossil hominids, we recognize them here as Homo sapiens idaltu, a new palaeosubspecies of Homo sapiens".

Stringer (2003), however, in a commentary article, suggests that the skulls may not be distinctive enough to warrant a new subspecies name.

Both anatomically and chronologically, the Herto skulls seem intermediate between earlier and more primitive skulls such as Bodo and Kabwe ('Homo rhodesiensis') and the first completely modern human skulls which are first found from about 115,000 years ago.

The authors' final conclusion is that "When considered with the evidence from other sites, this shows that modern human morphology emerged in Africa long before the Neanderthals vanished from Eurasia." Because of this, these finds have been generally seen as a setback for the Multiregional model of human evolution (which argues that modern humans evolved in geographically widespread areas of the world) and strong support for the competing Out Of Africa model (which argues that modern humans evolved in Africa and spread out from there, displacing any preexisting populations).

Creationist Responses

Answers in Genesis (AIG) argues, quite reasonably, that these fossils are so similar to modern humans that they don't constitute any problem for creationists - or, at least, to their own position. Reasons To Believe (RTB), an old-earth creationist ministry founded by Hugh Ross, takes the more surprising position that these fossils are of soulless animals that merely look like humans, and has accused AIG of "factual errors and distortions", to which AIG has responded energetically. RTB's position seems untenable to me: it's hard to see how anyone can credibly claim that fossils so remarkably similar to modern humans are animals. RTB appears to have a strategy that by definition excludes any possibility of transitional fossils: if scientists put a fossil in anything other than Homo sapiens sapiens, it is "not a modern human" and hence is an animal (no matter how trivial the differences); if they do put it in H. sapiens sapiens, of course, it's also not evidence for human evolution. Heads I win, tails you lose.

References

Clark J.D., Beyene Y., WoldeGabriel G., Hart W., Renne P., Gilbert H. et al. (2003): Stratigraphic, chronological and behavioural contexts of Pleistocene Homo sapiens from Middle Awash, Ethiopia. Nature, 423:747-52.

Stringer C.B. (2003): Out of Ethiopia. Nature, 423:692-4.

White T.D., Asfaw B., DeGusta D., Gilbert H., Richards G.D., Suwa G. et al. (2003): Pleistocene Homo sapiens from Middle Awash, Ethiopia. Nature, 423:742-7.

Links

Oldest human skulls found (Jonathan Amos, BBC)

Odd skulls from oldest modern humans (Richard Stenger, CNN)

This page is part of the Fossil Hominids FAQ at the talk.origins Archive.