3-4 minutes
By the end of the last ice age, some 10,000 years ago, most of Earth's
mammoths were gone. However, a few small, isolated populations pressed
on.
The mammoths living on Wrangel Island in the Arctic Ocean were one of
those isolated populations. The were likely some of the last mammoths on
Earth. They died out 3,700 years ago.
New research, published this week in the journal Genome Biology and
Evolution, suggests mutations accumulated in the genome of the Wrangel
Island mammoth population prevented their genes from functioning
properly.
Previous studies have shown that the mammoths living Wrangel Island
suffered from a variety of genetic defects. As isolated populations
decline, interbreeding and a lack of genetic diversity prevent species
from purging their genomes of mutations.
The latest research showed that many of these mutations were disruptive.
"The key innovation of our paper is that we actually resurrect Wrangel
Island mammoth genes to test whether their mutations actually were
damaging -- most mutations don't actually do anything," lead study
author Vincent Lynch, an evolutionary biologist at the University at
Buffalo, said in a news release. "Beyond suggesting that the last
mammoths were probably an unhealthy population, it's a cautionary tale
for living species threatened with extinction: If their populations stay
small, they too may accumulate deleterious mutations that can
contribute to their extinction."
In California, studies have shown that mountain lions hemmed in by
highways and other kinds of human development are suffering from low
levels of genetic diversity.
For the new study, scientists compared sequenced DNA recovered from the
remains of a Wrangel Island mammoth with the genomes of a pair of more
ancient mammoths from larger, more diverse populations. Researchers also
compared the mutation-rich mammoth genome with the genomes of three
Asian elephants.
The analysis revealed genetic mutations unique to the Wrangel Island
mammoth. In the lab, scientists synthesized the DNA mutations and
inserted them into cells in petri dishes. Tests showed the proteins
expressed by the mutated genes failed to interacted normally with other
genes and molecules.
"We know how the genes responsible for our ability to detect scents
work," Lynch said. "So we can resurrect the mammoth version, make cells
in culture produce the mammoth gene, and then test whether the protein
functions normally in cells. If it doesn't -- and it didn't -- we can
infer that it probably means that Wrangel Island mammoths were unable to
smell the flowers that they ate."
Authors of the new study suggest the latest findings complement the
results of a 2017 study that showed gene mutations impacted the
olfactory receptors of Wrangel Island mammoth, as well as their ability
to produce of certain urinary proteins -- mutations that may have
impacted mammoths' social status and mate choice.
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