Convoluted human evolution: early primates confuse (Introduction)

by David Turell @, Saturday, September 09, 2017, 15:27 (74 days ago) @ David Turell

The new fossil findings are not clarifying the arrival of primates, but a mix of confusing fossils starting 57 million years ago:

https://www.newscientist.com/article/2146797/

"Now a fossil discovered in France suggests the first primate might actually have been a bizarre monkey-like animal capable of acrobatic leaping. That makes it harder to work out what drove primate evolution.

"Primates first appear in the fossil record about 57 million years ago. They quickly divided into two groups – the “wet-nosed” primates that now include lemurs and the “dry-nosed” primates represented by tarsiers, monkeys, apes and humans.

"Primates on both sides of the divide have features in common, including grasping hands and feet, and nails rather than claws. This implies that these features evolved in the primate common ancestor.

***

"But a 52-million-year-old fossil ankle bone found near Marseilles, France, calls this idea into question. Boyer and his colleagues, who analysed the fossil, say it belonged to an early primate called Donrussellia provincialis, which was previously known only from fossil teeth.

"Boyer believes that D. provincialis is the most primitive wet-nosed primate so far discovered. What’s more, the shape and size of the ankle bone suggest D. provincialis was an adept leaper, flexing and quickly extending its ankle to launch into the air.

"That is significant, because recent discoveries suggest primitive dry-nosed primates were also good leapers. Archicebus achilles, described in 2013, had a long hindlimb and short forelimbs, which are characteristic of a leaping animal.

“'Donrussellia and Archicebus are definitely on opposite sides of the tree,” says Boyer. “So when they both have the suggestion of leaping traits, it starts to look like acrobatic leaping behaviours were important early in primate evolution.”

***

"If primates did begin as leapers, it will be harder to work out what drove their initial evolution, says Boyer. “It’s easy to understand how specialisation for navigating small branches would be beneficial, specifically for harvesting food objects that grow there. It’s hard to think of a simple scenario that would emphasise acrobatic leaping on its own.”

"Other fossils suggest that the first primate had extraordinarily long fingers, he says. “So you have this animal that was very acrobatic, probably leaping from large diameter supports – tree trunks – but at the same time it had almost monstrously long fingers that go beyond what’s required for grasping.”

"That is a weird combination of features, says Boyer. “But the insane thing is, researchers have discovered skeletons of fossil animals called apatemyids that appear just a few million years before the first primates, and have this same anatomical pattern.”

"While apatemyids are not directly related to primates, says Boyer, their similarities to the earliest primates may provide important clues about how our distant ancestors lived."

Comment: For early small mammals to enter trees they had to develop ways to get there. The period discussed is within the first ten million years after Chicxulub. Both legs and arms had to change form and function. It is easy to see purposeful planning for the future tree dwellers.


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