Early primate skeleton fills missing link of human evolution

A fossil primate skeleton, apparently the oldest ever found, has been unearthed in China, and this 'cousin' of humanity shows that some of our earliest ancestors were tiny, hyperactive bug-eaters, that were constantly on the move.

Somewhere around 55 million years ago, when mammals were still establishing themselves after 160 million years of dinosaur dominance, not to mention the meteorite strike that helped them out from underfoot in the first place, there was a split on the primate 'family tree'.

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One previous split in the tree had already branched off into what would develop into lemurs, and this second split produced two other branches, one that would develop into 'tarsiers', and one for 'anthropoids', that would eventually produce humans — with offshoots for monkeys, baboons and apes along the way. This second split has always been a bit of a murky spot for paleontologists, because there haven't been many fossils from that time period, but this newest discovery seems to fill in part of the gap.

This tiny fossil, named Archicebus achilles (or "ancient monkey"), is the most complete one that scientists have found from this point along the primate evolutionary tree, and it's about 7 million years older than the previous 'oldest' primate fossil found. Although it stands on the particular branch that leads towards the evolution of tarsiers, it's close enough to where that branch split off to give us some excellent insights into what all primates were like at that time.

When this little guy was alive, it was roughly 10 cm long (not including the tail) and about 20 to 30 grams, fully grown.

"It’s a cute little thing; it's ridiculously little," said Christopher Beard, curator at the Carnegie Museum of Natural History in Pittsburgh, according to The Globe and Mail. "That's one of the more important scientific aspects of the whole story."

This is because previous speculation about early primates said that they were larger, about the size of a modern monkey, but this new find shows that they were likely substantially smaller. Also, a warm-blooded creature that small would likely eat a diet of concentrated protein, such as insects, and would have to move constantly to stay warm, making them "very frenetic creatures, anxious, highly-caffeinated animals running around looking for their next meal," said Beard.

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There have been plenty of 'missing links' in the chain of evolution that leads from the lowest forms of life up to humans, and although we've found many fossils to fill spots along the chain, paleontologists continue on this adventure of discovery, piecing together how we developed into our current form. This particular find apparently opens up some questions about whether the branch of early primates happened in Asia, as opposed to Africa, but that's all a part of the science and all a part of the adventure.

"Archicebus marks the first time that we have a reasonably complete picture of a primate close to the divergence between tarsiers and anthropoids," Xijun Ni, a research associate at the American Museum of Natural History, said in a statement. "It represents a big step forward in our efforts to chart the course of the earliest phases of primate and human evolution."

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