Poaching is altering the genetics of wild animals
Elephants and other species are quickly adapting to human threats. Will that help them survive?
By Benji Jones@BenjiSJones Oct 21, 2021, 4:20pm EDT
Sometime in the distant past, well before humans walked the Earth, the ancestors of
modern-day elephants evolved their iconic tusks. Elephants use their bleach-white
incisors — they’re technically giant teeth, like ours but longer — to dig, collect food,
and protect themselves.
Then Homo sapiens arrived, and elephant tusks became a liability. Poachers kill the
massive animals for their tusks, which are worth about $330 a pound wholesale as
of 2017. Hunters slaughter roughly 20,000 elephants a year to supply the global
ivory trade, according to the World Wildlife Fund.
But just as tusks evolved because they provide a number of benefits, a striking new
study shows that some populations of African elephants have rapidly evolved to
become tusk–less. Published in the journal Science, the paper’s authors found that
many elephants were heavily hunted for their ivory during a civil war a few decades
ago, have lost their tusks — presumably because tuskless elephants are more likely
to survive and pass the trait on to their offspring.
It’s not uncommon to see tuskless elephants in places with lots of poaching — the
study provides strong evidence that the trait is rooted in genetics, something
previous research failed to do, said Andrew Hendry, an evolutionary biologist at
McGill University who was not involved in the research. In other words, the study
shows evolution in action.
The results also offer a vivid example of how animals can quickly adapt under
human pressures such as poaching and climate change. Past research has shown
that creatures can evolve new colours, shapes, and even behaviours to better
tolerate the increasingly inhospitable world we’ve created for them. The problem is
that even rapid evolution has its limits — and many species are already on the brink.
How a civil war caused elephants to lose their tusks
Social conflict and the decline of wildlife are often closely linked, the authors of
the Science study write. During a 16-year civil war that began in 1977, poachers on
both sides of the conflict slaughtered a huge number of elephants in the park for their
ivory, which they sold to finance their efforts, according to the study. Over that period,
the number of large herbivores (like elephants) fell by more than 90 percent.
Also, between 1970 and 2000 — a period that encompassed much of the impact of
the long-running war — the portion of female elephants without tusks nearly tripled.
The researchers’ best guess was that it had something to do with genetics: A trait
visible only in females suggests it might be associated with changes to genes on the
X chromosome. (Female elephants have two X chromosomes, whereas males have
an X and a Y chromosome.)
This study all but proved it. The first bit of evidence was that female calves born from
tuskless mothers were often themselves tuskless, indicating that the trait is passed
on from one generation to the next. “A heritable trait is pretty strong evidence of a
genetic basis,” said Robert Pringle, a biology professor at Princeton and a co-author
of the study.
Remarkably, one of the genes associated with tusklessness is also present in
humans, where it’s linked to a condition that limits the growth of our lateral incisors.
These are essentially the same teeth that, in elephants, evolved into tusks millions of
years ago.
What makes this study so fascinating is that it offers evidence of rapid evolution in an
animal that has a pretty long lifespan — 50 or 60 years — in the wild, said Hendry
and Fred Allendorf, a professor emeritus at the University of Montana who was not
involved in the research.
Studies of elephants “rarely can say anything about the genetic basis” of
tusklessness, Hendry said. For years, researchers assumed that rapid evolution was
common only in small species with short life cycles. Given these results, “Nobody
can argue that evolution isn’t occurring, even in the biggest and longest-lived
species,” he added.
Should all elephants ditch their tusks?
In theory, it’s advantageous to be born without tusks in areas where poachers are
active, Hendry said. But tusklessness also has its downsides. Elephants need their
tusks to dig, lift objects, and defend themselves. The hulking incisors are not useless
appendages.
The genes that seem to make female elephants tuskless also appear to prevent
mothers from giving birth to male calves — that’s why all the tuskless elephants in
the park are female, Pringle said. (Some mothers did give birth to males with tusks,
who likely didn’t inherit the gene.) Over time, a shift in the sex of elephants could
have consequences for population growth.
Conclusively, the tuskless elephants in this study are just one example in a long list
of species that have adapted in response to the pressures we’ve placed on them.
Retrieved and adapted from
https://www.vox.com/down-to-earth/22735163/elephant-tusks-genetics-evolution-ada
ptation-hunting