Earliest Known Human Relatives Came from Asia
A recreation of the newly found animal with its tooth. Marc Klinger
- A new fossil primate, Afrasia, is related to, but more primitive than, an early African primate from Libya.
- The find strengthens the belief that anthropoids originated in Asia.
- Afrasia and other Asian anthropoids likely migrated to Africa 37-38 million years ago.
The ancestors of humans, apes and monkeys evolved first in Asia before moving on to Africa, suggests a new fossil find from Myanmar.
Remains of a newly found primate, Afrasia djijidae, show this monkey-like animal lived 37 million years ago and was a likely ancestor of anthropoids -- the group including humans, apes and monkeys.
"Many people have heard about the 'Out of Africa' story of human origins and human evolution," said Christopher Beard, a Carnegie Museum of Natural History vertebrate paleontologist who co-authored a study about the fossil find in the latest Proceedings of the National Academy of Sciences. "Our paper is the logical precursor to that, because we are showing how the anthropoid ancestors of humans made their way 'Into Africa' in the first place."
He added, "We would not be here talking about this subject, or any other subject, if these early Asian anthropoids had not made that fateful voyage to Africa."
Beard, project leader Jean-Jacques Jaeger of the University of Poitiers, and their colleagues analyzed the tooth remains of Afrasia. They found that it is very similar to, but more primitive than, another early anthropoid, Afrotarsius libycus, recently discovered at a site of similar age in the Sahara Desert of Libya. (The term "anthropoid" is used instead of "primate" because all anthropoids are primates, but not all primates are anthropoids. Lemurs, for example, fall into that latter group.)
The tooth size of Afrasia and Afrotarsius indicates that in life, both animals only weighed around 3.5 ounces. They likely fed mostly on insects and probably resembled small monkeys, Beard said.
Although quite similar, the fossils differ in that Afrasia is more closely tied to the world's oldest known anthropoid, Eosimias, which lived between 40-45 million years ago in China.
It remains a mystery as to how the small Asian animals came to Africa.
"What we do know is that they had to cross a much larger version of the Mediterranean Sea (the ancient body of water was called the Tethys Sea) in order to go from Asia to Africa," Beard said. "At that time, Africa was an island continent like Australia is today."
He said one possibility is that the early Asian anthropoids rafted across the Tethys on a floating island of tree-covered land that may have eroded off large riverbanks in Asia during storms and floods. Beard explained, "There have been a few examples where scientists have found animals living on mats of vegetation like this, out at sea, following a hurricane or large storm."
Afrasia, he said, "is a close relative of humans and other living anthropoids. It is a member of an evolutionary side-branch of the monkey, ape and human family tree."
He and his colleagues suspect that this branch eventually went extinct. It is likely that multiple Asian anthropoid species were able to colonize Africa 38-37 million years ago, with one species evolving many years later into Homo sapiens.
So far, it appears that the close ancestors of Afrasia, which remained in Asia, also went extinct. Some anthropoids made the journey back to Asia from Africa, however. Orangutans, for example, made that trip about 10 to 15 million years ago.
"Human ancestors left Africa much more recently than that," Beard said, explaining that the oldest fossil human relatives outside of Africa are about 1.8 million years old. "They come from the former Soviet Republic of Georgia."
Scientists have long wondered why anthropoids just seemed to suddenly appear in Africa, with no apparent ancestry there. Afrasia's discovery helps to solve that mystery by opening up a new pre-chapter set in Asia.
"For years, we thought the African fossil record was simply bad," Jaeger said. "The fact that similar anthropoids lived at the same time in Myanmar and Libya suggests that the gap in early African anthropoid evolution is actually real. Anthropoids didn't arrive in Africa until right before we find their fossils in Libya."