Earliest human remains in eastern Africa dated to more than 230,000
years ago

Date:
January 12, 2022
Source:
University of Cambridge
Summary:
The age of the oldest fossils in eastern Africa widely recognized
as representing our species, Homo sapiens, has long been
uncertain. Now, dating of a massive volcanic eruption in Ethiopia
reveals they are much older than previously thought.



FULL STORY ==========================================================================
The age of the oldest fossils in eastern Africa widely recognised as representing our species, Homo sapiens, has long been uncertain. Now,
dating of a massive volcanic eruption in Ethiopia reveals they are much
older than previously thought.


==========================================================================
The remains -- known as Omo I -- were found in Ethiopia in the late 1960s,
and scientists have been attempting to date them precisely ever since,
by using the chemical fingerprints of volcanic ash layers found above
and below the sediments in which the fossils were found.

An international team of scientists, led by the University of Cambridge,
has reassessed the age of the Omo I remains -- and Homo sapiens as
a species.

Earlier attempts to date the fossils suggested they were less than
200,000 years old, but the new research shows they must be older than
a colossal volcanic eruption that took place 230,000 years ago. The
results are reported in the journal Nature.

The Omo I remains were found in the Omo Kibish Formation in southwestern Ethiopia, within the East African Rift valley. The region is an area
of high volcanic activity, and a rich source of early human remains and artefacts such as stone tools. By dating the layers of volcanic ash above
and below where archaeological and fossil materials are found, scientists identified Omo I as the earliest evidence of our species, Homo sapiens.

"Using these methods, the generally accepted age of the Omo fossils is
under 200,000 years, but there's been a lot of uncertainty around this
date," said Dr Ce'line Vidal from Cambridge's Department of Geography,
the paper's lead author. "The fossils were found in a sequence, below
a thick layer of volcanic ash that nobody had managed to date with
radiometric techniques because the ash is too fine-grained." As part
of a four-year project led by Professor Clive Oppenheimer, Vidal and her colleagues have been attempting to date all the major volcanic eruptions
in the Ethiopian Rift around the time of the emergence of Homo sapiens,
a period known as the late Middle Pleistocene.



==========================================================================
The researchers collected pumice rock samples from the volcanic deposits
and ground them down to sub-millimetre size. "Each eruption has its own fingerprint -- its own evolutionary story below the surface, which is determined by the pathway the magma followed," said Vidal. "Once you've
crushed the rock, you free the minerals within, and then you can date
them, and identify the chemical signature of the volcanic glass that
holds the minerals together." The researchers carried out new geochemical analysis to link the fingerprint of the thick volcanic ash layer from the Kamoya Hominin Site (KHS ash) with an eruption of Shala volcano, more
than 400 kilometres away. The team then dated pumice samples from the
volcano to 230,000 years ago. Since the Omo I fossils were found deeper
than this particular ash layer, they must be more than 230,000 years old.

"First I found there was a geochemical match, but we didn't have the age
of the Shala eruption," said Vidal. "I immediately sent the samples of
Shala volcano to our colleagues in Glasgow so they could measure the age
of the rocks. When I received the results and found out that the oldest
Homo sapiens from the region was older than previously assumed, I was
really excited." "The Omo Kibish Formation is an extensive sedimentary
deposit which has been barely accessed and investigated in the past," said co-author and co-leader of the field investigation Professor Asfawossen
Asrat from Addis Ababa University in Ethiopia, who is currently at
BIUST in Botswana. "Our closer look into the stratigraphy of the Omo
Kibish Formation, particularly the ash layers, allowed us to push the
age of the oldest Homo sapiens in the region to at least 230,000 years." "Unlike other Middle Pleistocene fossils which are thought to belong to
the early stages of the Homo sapienslineage, Omo I possesses unequivocal
modern human characteristics, such as a tall and globular cranial vault
and a chin," said co-author Dr Aure'lien Mounier from the Muse'e de
l'Homme in Paris. "The new date estimate, de facto, makes itthe oldest unchallenged Homo sapiens in Africa." The researchers say that while
this study shows a new minimum age for Homo sapiens in eastern Africa,
it's possible that new finds and new studies may extend the age of our
species even further back in time.



==========================================================================
"We can only date humanity based on the fossils that we have, so it's impossible to say that this is the definitive age of our species,"
said Vidal.

"The study of human evolution is always in motion: boundaries and
timelines change as our understanding improves. But these fossils show
just how resilient humans are: that we survived, thrived and migrated
in an area that was so prone to natural disasters." "It's probably no coincidence that our earliest ancestors lived in such a geologically
active rift valley -- it collected rainfall in lakes, providing fresh
water and attracting animals, and served as a natural migration corridor stretching thousands of kilometres," said Oppenheimer. "The volcanoes
provided fantastic materials to make stone tools and from time to time
we had to develop our cognitive skills when large eruptions transformed
the landscape." "Our forensic approach provides a new minimum age
for Homo sapiens in eastern Africa, but the challenge still remains
to provide a cap, a maximum age, for their emergence, which is widely
believed to have taken place in this region," said co-author Professor Christine Lane, head of the Cambridge Tephra Laboratory where much of the
work was carried out. "It's possible that new finds and new studies may
extend the age of our species even further back in time." "There are
many other ash layers we are trying to correlate with eruptions of the Ethiopian Rift and ash deposits from other sedimentary formations," said
Vidal. "In time, we hope to better constrain the age of other fossils in
the region." The research was supported in part by the Leverhulme Trust,
the Cambridge- Africa ALBORADA Research Fund and the Natural Environment Research Council.

Ce'line Vidal is a Fellow of Fitzwilliam College, Cambridge.

========================================================================== Story Source: Materials provided by University_of_Cambridge. Original
written by Sarah Collins. The original text of this story is licensed
under a Creative_Commons License. Note: Content may be edited for style
and length.


========================================================================== Related Multimedia:
* Omo-Kibish_skull_and_land_formation ========================================================================== Journal Reference:
1. Ce'line M. Vidal, Christine S. Lane, Asfawossen Asrat, Dan
N. Barfod,
Darren F. Mark, Emma L. Tomlinson, Amdemichael Zafu Tadesse,
Gezahegn Yirgu, Alan Deino, William Hutchison, Aure'lien Mounier
& Clive Oppenheimer. Age of the oldest known Homo sapiens from
eastern Africa.

Nature, 2022 DOI: 10.1038/s41586-021-04275-8 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220112121507.htm
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