Wednesday, June 7, 2017

300,000 Year Old Modern Human Bones Found In Morocco

Image from here.

Just two days after a paper analyzing 2000 year old Khoi-San DNA from South Africa and determining that the Khoi-San divergence date from other African populations was ca. 260,000 years ago, there is an announcement that an anatomically modern human bone that is 300,000 years old has been found, much older than the oldest accurately dated modern human remains previously known from about 195,000 years ago in Ethiopia.
The oldest fossil remains of Homo sapiens, dating back to 300,000 years, have been found at a site in Jebel Irhoud, Morocco. This is 100,000 years older than previously discovered fossils of Homo sapiens that have been securely dated. The discovery was presented in a study in the journal Nature on Wednesday. 
This marks the first discovery of such fossils in north Africa, and widens the "cradle of mankind" to encompass all of Africa, the researchers said. Previous finds were in south or east Africa. The fossils, including a partial skull and a lower jaw, belong to five different individuals including three young adults, an adolescent and a child estimated to be 8 years old. Stone tools, animal bones and evidence of fire were also found within the same layer at the site.
This result doesn't strongly contradict the current paradigm, but does clearly push it in the direction of older anatomically modern human speciation (Y-DNA had pointed to a date about 270,000 years ago), and a wider geographic range within Africa of early modern humans. This also brings the speciation date closer to the divergence date for other archaic hominins like Neanderthals and Denisovans.

The abstract and citation to the paper are as follows:
The timing and location of the emergence of our species and of associated behavioural changes are crucial for our understanding of human evolution. The earliest fossil attributed to a modern form of Homo sapiens comes from eastern Africa and is approximately 195 thousand years old1, 2, therefore the emergence of modern human biology is commonly placed at around 200 thousand years ago3, 4. The earliest Middle Stone Age assemblages come from eastern and southern Africa but date much earlier5, 6, 7. Here we report the ages, determined by thermoluminescence dating, of fire-heated flint artefacts obtained from new excavations at the Middle Stone Age site of Jebel Irhoud, Morocco, which are directly associated with newly discovered remains of H. sapiens8. A weighted average age places these Middle Stone Age artefacts and fossils at 315 ± 34 thousand years ago. Support is obtained through the recalculated uranium series with electron spin resonance date of 286 ± 32 thousand years ago for a tooth from the Irhoud 3 hominin mandible. These ages are also consistent with the faunal and microfaunal9 assemblages and almost double the previous age estimates for the lower part of the deposits10, 11. The north African site of Jebel Irhoud contains one of the earliest directly dated Middle Stone Age assemblages, and its associated human remains are the oldest reported for H. sapiens. The emergence of our species and of the Middle Stone Age appear to be close in time, and these data suggest a larger scale, potentially pan-African, origin for both.
Daniel Richter, et al., "The age of the hominin fossils from Jebel Irhoud, Morocco, and the origins of the Middle Stone Age" 546 Nature 293–296 (June 7, 2017).

A sister paper discusses the taxonomy of these remains and assigns them to the "early stages of the H. sapiens clade" despite a mosaic and archaic and primitive features. It may be more fair to classify these remains as transitional between archaic and anatomically modern human, rather than a completely anatomically modern human individual. John Hawks is tweeting his skepticism about the classification of these remains as Homo sapiens with a cogent and fuller explanation here.
Fossil evidence points to an African origin of Homo sapiens from a group called either H. heidelbergensis or H. rhodesiensis. However, the exact place and time of emergence of H. sapiens remain obscure because the fossil record is scarce and the chronological age of many key specimens remains uncertain. In particular, it is unclear whether the present day ‘modern’ morphology rapidly emerged approximately 200 thousand years ago (ka) among earlier representatives of H. sapiens1 or evolved gradually over the last 400 thousand years2. Here we report newly discovered human fossils from Jebel Irhoud, Morocco, and interpret the affinities of the hominins from this site with other archaic and recent human groups. We identified a mosaic of features including facial, mandibular and dental morphology that aligns the Jebel Irhoud material with early or recent anatomically modern humans and more primitive neurocranial and endocranial morphology. In combination with an age of 315 ± 34 thousand years (as determined by thermoluminescence dating)3, this evidence makes Jebel Irhoud the oldest and richest African Middle Stone Age hominin site that documents early stages of the H. sapiens clade in which key features of modern morphology were established. Furthermore, it shows that the evolutionary processes behind the emergence of H. sapiens involved the whole African continent.
Jean-Jacques Hublin, et al., "New fossils from Jebel Irhoud, Morocco and the pan-African origin of Homo sapiens" 546 Nature289–292 (June 7, 2017)


Ryan said...

I think the question of whether or not this skull is from a migration out of or into Sub-Saharan Africa deserves a lot of scrutiny.

andrew said...

I think that the question of whether or not this skull is from a migration out of or into Sub-Saharan Africa is almost surely unanswerable until we have far more evidence. Middle Paleolithic hominin remains are to few and far between to meaningfully answer a question like that one, despite the willingness of folks like Dienkes' to stick his neck out in favor of a particular position without much solid evidence to back it up.

Ryan said...

Denekies has had a pretty good track record on things he's stuck his neck out on so far though lol.

I agree it's not really answerable right now, but the fact that there is meaningful debate and doubt about this is I think a pretty big development.