ScienceCast: Origins of the Endangered Przewalski’s Horse

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An endangered species of horse — known as
Przewalski’s horse — is much more distantly related to the domestic horse than researchers
had previously hypothesized, reports a team of investigators led by Kateryna Makova, a
Penn State University associate professor of biology. The scientists tested the portion
of the genome passed exclusively from mother to offspring — the mitochondrial DNA — of
four Przewalski’s horse lineages and compared the data to DNA from the domestic horse. Przewalski’s horse — a stocky, short-maned
species named after a Russian explorer who first encountered the animal in the wild — became
endangered during the middle of the last century when the species experienced a population
bottleneck — an evolutionary event in which many or most members of a population or a
species die. Przewalski’s horses were hunted down for food, and their natural habitat,
the steppes, were converted into farm land so the horses basically had nowhere to live
and breed. By the late 1950s, only 12 individual horses remained. Because conservationists
have made noble efforts to rescue this dwindling population, the present-day population has
grown to 2,000. “Scientists thought previously that perhaps
this horse is the direct progenitor of the domestic horse. There was also another idea
that perhaps the domestic horse is the direct ancestor of the Przewalski’s horse.” Makova’s team discovered that neither scenario
is likely. Instead, her team’s data suggest that Przewalski’s horse and the domestic horse
are much more distantly related. In fact, they probably shared a common ancestor as
far back as 160,000 years ago, long before horse domestication. Although the two species diverged well over
100,000 years ago, they have interbred periodically since then. Also fortunate is the fact that
conservationists not only began new breeding efforts and built wildlife reserves, but they
also made sure to avoid inbreeding among close relatives. “So now as we have the complete sequences
of mitochondrial DNA for all four surviving maternal lineages of Przewalski’s horses,
now we can make very informed decisions about the subsequent breeding efforts and the subsequent
reproduction efforts into the wild.” For ScienceCast, I’m Christina Ombalski.


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