Global cooling: Chinese study reveals how a big chill killed off potential human origins in Asia

Research answers question why Africa became the centre of evolution for primates

PUBLISHED : Saturday, 07 May, 2016, 11:00am
UPDATED : Monday, 12 June, 2017, 12:53pm

Humans could have originated in Asia if not for a massive cooling event that wiped out all large primates in the region some 34 million years ago, according to a joint study by Chinese and US scientists.

The research team led by professor Ni Xijun, from the Chinese Academy of Sciences’ Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, came to the conclusion after analysing the fossils of six new species of early primates found in southwest China.

The findings are reported in the latest issue of Science magazine.

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The primates all went extinct during the period known as Eocene-Oligocene transition, when most of the earth, except for Africa and Southeast Asia, experienced a rapid drop in temperature and humidity because of tectonic shifts.

The research answered a question that had puzzled scientists for decades: why did humans originate in Africa when the earliest primate fossils have been found in Asia dating back 45 million years ago?

“After going through the ‘voluntary filter’ of the Eocene-Oligocene transition, the anthropoids [large primates] in Asia went extinct but the anthropoids in Africa began to thrive, eventually leading to monkeys, apes and human beings,” Xinhua quoted Ni as saying.

“This study reveals why Africa became the centre of evolution for primates.”

K Christopher Beard, senior curator at the University of Kansas’ Biodiversity Institute and co-author of the paper, told Phys.org that the ancient Chinese primates might have lived in trees in tropical forests.

One species was “incredibly similar” to the modern tarsier in the Philippines and Indonesia today.

If not for the intense global cooling of the Eocene-Oligocene transition, the main stage of primate evolution might have continued to be in Asia rather than transitioning to Africa, Beard said.

“This is the flip side of what people are worried about now,” Phys.org quoted him as saying.

“The Eocene-Oligocene transition was the opposite of global warming – the whole world was already warm, then it cooled off. It’s kind of a mirror image. The point is that primates then, just like primates today, are more sensitive to a changing climate than other mammals.”

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But retired paleoanthropologist professor Wei Qi said the new study might have overestimated the impact of climate change because the cooling event 34 million years ago was quite a long time before the emergence of the earliest humanoids some 2.8 million years ago.

“Some primates might still have survived in Asia after the Eocene-Oligocene transition, and we just haven’t found their fossils yet,” he said.

“To rule out the possible of Asian origin with a few fragments of jaws and teeth is to make a big claim with little evidence.”