A fossilised skeleton of
a tiny creature with a long tail, sharp teeth and monkey-like feet has turned
out to be the oldest-known primate – the group that includes gorillas, chimps
and humans.
Scientists discovered the
fossil in the solidified sediment of an ancient lake bed in China and have
dated it to about 55 million years ago, about 10 million years after the demise
of the dinosaurs and seven million years before the date of the previous
oldest-known primate.
The researchers said it
is one of the most exciting fossil discoveries in recent years because the
animal – called Archicebus achilles – is the closest-known relative of the
common ancestor to the entire “anthropoid” lineage encompassing monkeys, apes
and man.
Archicebus grew no bigger
than a modern-day pygmy shrew and from its relatively small eye sockets
scientists believe it was active during the day rather than at night, feeding
off insects and small invertebrates.
“Archicebus differs
radically from any other primate, living or fossil, known to science,” said
Christopher Beard of the Carnegie Museum of Natural History in Pittsburgh,
co-author of the fossil’s scientific description, published in the journal
Nature. “It looks like a hybrid with the feet of a small monkey, the arms, legs
and teeth of a very primitive primate and a primitive skull bearing
surprisingly small eyes. It will force us to re-write how the anthropoid
lineage evolved,” Dr Beard said.
Although Archicebus
(which means “first, long-tailed monkey”) is close to the common ancestor of
all anthropoids, scientists believe it was not a direct ancestor of humans but
instead had begun to evolve along the alternative primate lineage that
eventually gave rise to the tarsiers – a specialised group of small, nocturnal
primates.
“This is not a direct
ancestor of humans but for the first time it sheds light on this pivotal
episode of primate evolution when two branches of primates – the anthropoids
and the tarsiers – split apart,” Dr Beard said.
A farmer discovered the
fossil in an ancient lakebed in China’s Hubei Province
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