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Thursday, June 22, 2017

Homo sapiens from Jebel Irhoud at 315 ka

New fossils from Jebel Irhoud, Morocco and the pan-African origin of 
Homo sapiens. 


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. sapiens or 
evolved gradually over the last 400 thousand years. 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), 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. 

The age of the hominin fossils from Jebel Irhoud, Morocco, and the 
origins of the Middle Stone Age. 


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 old, therefore the emergence of modern human biology is 
commonly placed at around 200 thousand years ago. The earliest Middle 
Stone Age assemblages come from eastern and southern Africa but date 
much earlier. 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. sapiens. 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 microfaunal assemblages and almost double the previous age 
estimates for the lower part of the deposits. 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. 



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