Home Evolution Ancient primate fossils calls into question ape evolution

Ancient primate fossils calls into question ape evolution

Scientists have uncovered ancient primate fossils that may force us to rethink how apes evolved.

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"White-handed Gibbon Hylobates lar Orange 1900px" by Photo by Derek Ramsey (Ram-Man) - Self-photographed. Licensed under CC BY-SA 2.5 via Commons

The evolution of great apes, and by extension humanity, remains one of the hottest topics in science. Over the last few years a “clear” picture of ape evolution, with a “neat” break between monkeys and apes 18 million years ago, has emerged. Now this evolution is being called into question by a recent discovery of a 11.6 million year old Pliobates fossil in Spain that suggests the break may not have been so clean after all.

Researchers uncovered the ancient primate fossils in Catalonia. They appear to belong to what was a small, herbivore primate that preferred to munch on fruit. Interestingly, the primate lived alongside massive saber-toothed predators, rhinos, and other mega-beasts, sharing space in a warm, wet forest.

The fossils found included 70 bones and bone fragments. Among the bones was a well preserved skull, one of the best for a primate so old.

As is common among primate fossils, this miniature ape was given a name, “Laia”.  The animal is estimated to have weighed only 9 to 11 pounds, making it smaller than many modern monkeys.

Scientifically, the primate is called a Pliobates. The animal is especially interesting as it appears to be a sort of intersection between more primitive primates and modern ones, exhibiting features from both.  As a sort of “stepping stone” animal, it could help researchers learn more about how primates evolved.

As paleobiologist David Alba of the Catalan Institute of Paleontology put it “We can imagine a small ape, like the smallest living gibbons, with a gibbon-like appearance regarding the cranium but with different body proportions: less elongated arms and hands.”

This might seem like some rather unimportant details, but for primates these stubby arms would have a big impact on how they lived their life. Researchers believe the primate would have had to move through the forest canopy more slowly, and deliberately.

The skull of the primate shares some commonalities to modern apes, as does its elbows and wrists. Other things, like teeth and ears, are more similar to ancient primates, however.

So why would this matter? As Alba puts it, “Pliobates suggests that small-bodied apes played a much more important role in the origin of extant apes than previously recognized, and that their last common ancestor, in several respects, skull shape and body size, might have been more gibbon-like than previously thought.”

Importantly, the discovery hints that the predecessors to apes and even humans may have been smaller than previously believed. Scientists had previously assumed that by 10 million years ago, “great” apes were already emerging. The recent finding suggests that such apes might not have emerged until later.

Apes and monkeys are believed to have split in their evolutionary paths about 25 million years ago. Then about 17 million years ago apes split into “lesser” and “greater” apes. Humans evolved from the latter.

This previously assumed “neat” split that supposedly occured 18 million years ago, however, is now being called into question. The gibbon-like Pliobates shares too many traits in common to be ignored as a possible forebearer for great apes, even in spite of its tiny size. Still, scientists currently believe that this “mini ape” lived too recently to be the common ancestor for all apes and humans.

The findings were published in the journal Science.