5 March 2022 | New Scientist | 19News
THE biggest family tree of
humanity to date has been built
using genetic data from thousands
of modern and prehistoric people.
The tree gives a view of 2 million
years of prehistory and evolution.
“Humans are all ultimately
related to each other,” says Gil
McVean at the University of
Oxford. “What I’ve long wanted
to do is to be able to represent
the totality of what we can learn
about human history through
this genealogy.”
Geneticists have been reading
people’s entire genomes for the
past two decades. McVean and
his colleagues compiled 3609
of these, almost all of which
belonged to our species, Homo
sapiens, except for three
Neanderthals and one from
the Denisovan group, which
may be a subspecies of H. sapiens
or a separate species.
Putting them together into
a tree was challenging. “The
different data sets have been
produced over time, using
different technologies, analysed
in different ways,” says McVean.
The team focused on bits of
DNA that vary from person to
person. They identified 6,412,717
variants and tried to figure out
when and where each arose. To do
this, they also looked at an extra
3589 samples of ancient DNA that
weren’t good enough to include
in the tree, but did shed light on
when the variants emerged.
Variants that emerged before
72,000 years ago were mostcommon in north-east Africa, and
the oldest 100 variants were also
from there, specifically in what is
now Sudan. Those oldest variants
are about 2 million years old, so
long predate our species, which
emerged around 300,000 years
ago. Instead, they date to the
earliest members of our genus,
Homo (Science, doi.org/hh3h).
The simplistic interpretation of
this is that humanity first evolved
in this region, but later migrations
are likely to have interfered with
the data. “I would definitely nottake the naive and immediate
answer,” says Jennifer Raff at
the University of Kansas.
The earliest H. sapiens fossils are
from the north and east of Africa,
but few have been discovered,
so we don’t know our species’
early range with any certainty.
Many anthropologists now
think multiple populations were
spread across Africa, which were
sometimes apart and sometimes
interbred. If that is correct,
humanity doesn’t have a
central origin point.
“Our findings are certainly
perfectly compatible with that,”
says McVean. “There’s a lot of very
deep lineages within Africa, which
are suggestive of that notion
of there being multiple source
populations, very deeply diverged,
representing really ancient splits.”
The tree also offers clues
that people reached Papua New
Guinea and the Americas tens
of thousands of years earlier than
the archaeological record implies,
hinting at migrations that have yet
to be discovered. But both these
ideas would need to be confirmed
by archaeological finds. ❚Evolution
Michael Marshall
WOHNS^ ET^ AL.^ (2022)Largest ever family tree of humanity
reveals history of our species
Family ties between
genomes visualised
as lines on a mapEnergy
THE cost of a proposed underground
storage facility to safely house the
UK’s nuclear waste for millennia
has risen to as much as £53 billion,
more than double the previous
estimate, according to a new
government report.
The UK currently stores
its 133,000 cubic metres of
radioactive waste above ground,
and the quantity is projected to
swell to more than 4 million cubic
metres in future. In 2018, the
government rebooted its search for
a community in England willing to
host an underground store, known
as a geological disposal facility,
after a previous effort was rejected
by local authorities in 2013.
Four years ago, the project
was estimated to cost between
£12 billion and £20 billion to build
and operate for 150 years. However,
in an annual report published on
18 February, UK government agency
Nuclear Waste Services (NWS)
revised the figure up to between
£20 billion and £53 billion. The
cost will be shouldered by taxpayersand nuclear power operators,
with each paying roughly half.
John Corderoy at NWS says the
huge increase is due to a broader
scope of costs and being more
realistic. The wide range of the
estimate is due to the potentially
large differences in where the
facility could be situated.
But the biggest increase
comes from expecting more
waste, including legacy radioactivematerial from a fleet of new nuclear
plants, as well as uranium and
plutonium that were deemed
an asset in the past, but are now
considered waste. “We’re counting
more things,” says Corderoy.
Roy Payne at GDFWatch, a UK
non-profit that tracks this issue,
says: “The initially eye-popping
increase in the upper projected
costs can probably be explained
by the change of management
and culture at NWS that takes
a more informed and realistic
view of the project, the external
market and geopolitical factors.” ❚Price tag rises for
UK’s planned nuclear
waste facility
Adam Vaughan4 million
Projected quantity of the UK’s
radioactive waste, in cubic metresInferred human ancestral lineagesGenerations ago100 1000 10,00050,000