4 April 2020 | New Scientist | 43Graham Lawton is a feature
writer for New Scientist. He
is author of This Book Could
Save Your Life, out nowtowards a recent origin. “This is
something we have to address,” says
Schlebusch. But she points to several
reasons to doubt the result. For a start,
mitochondrial DNA is informative
about maternal lineages, but not
about entire ancient populations. Just
because all Africans are descended
from a mitochondrial Eve who lived in
Botswana 200,000 years ago doesn’t
mean that they are only descended
from her. They could also have had
many other female ancestors whose
mitochondrial lineages died out.
Indeed, a similar analysis of
Y-chromosomes, passed exclusively
down the paternal lineage, points to
a Y-chromosome Adam in western
Africa 400,000 years ago. Only by
looking at full genomes can the whole
picture be inferred, and these point to
a pan-African origin, says Schlebusch.
In addition, there is all that evidence
from tools and fossils. “Single-place
origin is not the best model to describe
what actually happened in Africa,”
she says. “It’s more like a river delta
splitting and merging through time.”
So where do we stand? For now,
African multiregionalism looks like the
best effort at a coherent new synthesis.
Just don’t bet on it lasting as long even as
the recent out-of-Africa model. Future
discoveries will undoubtedly throw
more spanners in the works. The study
of ancient African genomes is in its
infancy. “Genomic data now drives the
subject, and it drives it very fast,” says
Foley. But there are surely more fossils
to find, too. The Middle Stone Age of
west Africa is essentially unexplored
and, as we have seen, a single skull can
bring entire models tumbling down.
In addition, there are 25 known taxa of
hominins that have yet to be integrated
into our tale. “It’s not going to be a
simple story,” says Foley. “We have to
think more flexibly and broadly about
the processes that are involved.”
Three days might be too short a
timescale for almost everything to
change. But three years from now,
who knows? ❚WHAT DROVE THE EVOLUTION
OF THE MODERN MIND?
Some 320,000 years ago, a
technological revolution swept across
Africa. The large, flat, leaf-shaped
hand axes that had remained largely
unchanged for 700,000 years
suddenly gave way to a more
sophisticated toolkit of smaller,
finer points and projectiles.
Palaeoanthropologists increasingly
recognise this transition as indicating
the dawn of the modern mind,
when people who looked like us
also began to think like us. It wasn’t
just a technological revolution but
a cognitive one too.
One of the best places to see this
on the ground is the Rift valley in
Kenya, in particular at a site called
Olorgesailie, an ancient lake bed rich
in stone tools. The transition is stark,
says Richard Potts at the Smithsonian
Institution in Washington DC. “We
have layer after layer of hand axes
then, no more hand axes.” What you
see instead is the more sophisticated
tools. But, unfortunately, erosion
at Olorgesailie means that the
sedimentary record has a gap of
around 180,000 years between
these two technologies. What was
happening at this crucial time to
drive this epochal change?
A few years ago, Potts and histeam drilled a core some 25 kilometres
away in an area with a complete
sedimentary record. The core is too
narrow to capture tools but it tells
a story of dynamic environmental
upheaval about half a million years
ago. “You have this complex and really
interesting combination of faulting,
breaking up of the landscape and
climate variability,” says Potts. “All
hell breaks loose.”
So far, evidence of cataclysmic
change has been seen only at the drill
site – a “pinprick in the Rift valley”, as
Potts describes it. But he says he would
expect to see it in other locations too.
“We may be wrong, but at least in the
place where we’re working in southern
Kenya, this is what the picture shows.”
The region around Olorgesailie also
records a major shift in the animals
present at this time, with large-bodied
grazing animals giving way to smaller
and presumably harder-to-catch ones.
“It’s an entirely changed ecological
setting in which early hominins had to
adapt,” says Potts. He thinks this wildly
unpredictable environment may have
been the selection pressure that drove
the evolution of modern behaviour.
“Flexibility becomes the new currency
of evolution,” he says. We had to think
smarter to survive.Human creativity
must long
predate these
30,000-year-old
cave paintings at
Chauvet, FranceAN
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