YSM Issue 96.2

Palaeogenomics
FEATURE
might have
e n c o u n t e r e d
along the way, but
this method of data
collection and analysis can
quantitatively prove or disprove
these conclusions.
The researchers also considered a
multitude of other factors, including
the radiocarbon dates of the materials,
so that they can pinpoint the age
of the samples and discover other
archaeological information. Simply,
radiocarbon dating is the process by
which researchers analyze the amount
of radioactive carbon-14 left in a sample
in order to measure its age. Further,
cultural information about specific
hunter-gather groups, such as knowledge
about their mortuary practices or the
types of weaponry they commonly used,
allowed the researchers to make
increasingly sound conclusions about the
movements of certain hunter-gatherer
groups and their possible relations to
other groups.
With this research, Yu and her team of
researchers have established a genomic
study of remarkable depth and breadth.
By drawing on multitudes of biological
and historical information, they created
a firmly-rooted “family tree” for huntergatherer
groups.
When working with a data set that is so
ancient, many challenges can arise. The
majority of the time, the samples used
usually come from bones or teeth. These
physical samples last through the ages
which makes them strong candidates
for DNA extraction. In especially old
samples, however, the DNA degenerates
and is poorly preserved. “The samples
that are reported, of course, are not the
only samples that we have processed.
There were various samples that did not
produce enough DNA and some which
had none at all, failing during the DNA
extraction process,” Yu said.
Even when a sample does
produce enough DNA, that data
must be observed with a critical eye. As
these samples have often been studied by
multiple parties and transported across
the globe, the risk for contamination is
high. “For many samples, we also had a
hard time trying to detect and confirm if
they are contaminated or not. Further, if
samples were found to be contaminated,
we then had to go through the process
of separating the DNA of that specimen
from its contaminants so that we could
get real information,” Yu said.
This study showed that huntergatherer
groups flocked to western and
southwestern Europe to escape the Ice
Age. “It was always assumed that the
Iberian Peninsula was a refuge during
the Ice Age, but this is the first time we
genetically confirmed that there is really a
human population—with the same genetic
ancestry found earlier in other regions of
Europe—living in that area,” Yu said. This
is a powerful confirmation that paints a
clearer picture of the survival, migration,
and mixing of hunter-gatherer groups.
But researchers still have questions,
especially about the importance of another
region as a refuge during the Ice Age: the
Italian Peninsula. In this region, there
were massive genomic changes before
and after the Ice Age, so researchers
cannot make a succinct conclusion on
whether or not it was a refuge based
on DNA evidence alone. These
regions saw a huge genomic
turnover, with distinct genetic populations
before and after the LGM. “Genetic
information could help us to answer or
confirm some points, but it alone cannot
confirm them all. It is important in these
sorts of studies to combine information
from different sources and evidence from
different disciplines,” Yu said.
History itself is expansive, and trying to
capture the movement of many different
groups over tens of thousands of years is an
exceedingly difficult task, but researchers
like Yu and her team are embarking on this
journey through time to reveal important
information about how our earliest
ancestors survived and how all of us are
here today. As we move forward and learn
more about our personal genomic histories
through popular testing platforms, we can
appreciate the work they are doing to
capture the genomic ancestry of
humans across the world. ■
www.yalescientific.org
May 2023 Yale Scientific Magazine 31