(USA TODAY) -- Gene experts said Wednesday they've been able to unravel the genetic
blueprint of a prehistoric horse that lived in Canada some 700,000 years
ago, the oldest DNA mapping effort ever attempted.
extension of the limits of ancient DNA recovery, the advance re-creates a
gene map, or genome, which is roughly 10 times older than the previous
record-holder. The feat suggests that ancient DNA may be recoverable
from frozen remains almost a million years old, raising the possibility
of someday recovering even more ancient gene maps of humanity's
"Obviously (this) opens great perspective as
to the level of details we could reconstruct of our own origins," says
study lead author Ludovic Orlando of Denmark's University of Copenhagen.
"And actually the evolutionary history of almost every species living
in the world today."
A research team in 2003 discovered the horse
bones encased in the oldest known permafrost, at the Thistle Creek
site in Canada's Yukon. The bones initially yielded promising signs of
blood and other tissues, which encouraged the team to try DNA mapping.
For comparison, the team also genetically mapped a DNA sample from a
43,000-year-old-horse, similarly frozen, as well as five modern horses, a
donkey and a modern-day Przewalski's horse.
Horses as a distinct
species appear to have split from donkeys 4 million years ago. The
results also confirm the Przewalski's horse, an endangered breed now
found in zoos and sanctuaries in Mongolia, as the last wild survivor of
all horses, splitting from domestic horses about 50,000 years ago. The
genes indicate that horse populations went through a series of booms and
busts tied to various Ice Ages that expanded grasslands over the last 2
million years. It also points to a genetic "bottleneck" that horses
went through on their way to domestication, finding genes related to
blood cells, fertility, color and muscle unique to modern horses and
absent in their ancient counterparts.
The team assembled the
700,000-year-old gene map using "short" DNA sequences preserved in a leg
bone, a capability that technology has only recently afforded to
researchers. Had the DNA not been frozen for the entirety of the time
since the horse died, team members expressed doubt that even that would
have been possible. In theory, the ancient horse DNA could be
reconstructed and used to clone a version of the now-extinct species, a
kind of "de-extinction" now widely debated by genetics researchers.
in between a pointer to the future and a one-off," says evolutionary
molecular biologist Tara Fulton of the University of California, Santa
Cruz, who was not on the study team. "It is also a matter of finding
these specimens in the permafrost or sometimes in consistently cool
northern caves and even in ideal preservational conditions. The DNA is
unlikely to survive too much past a million years."
Other researchers go further. Given that ancient human species at
times lived in cold climes, the ancient horse gene map raises the
possibility of recovering even more ancient human DNA, suggests
biologist Craig Millar of New Zealand's University of Auckland and David
Lambert of Australia's Griffith University, in a commentary on the
discovery. The results, they write, raise "the tantalizing proposition
that complete genomes several millions of years old may be recoverable."