Small-bodied, long-armed apes called gibbons dart through the trees, far outpacing scientists’ attempts to decipher the evolutionary history of these creatures.
Now a partial upper jaw and seven isolated teeth found near a village in southwestern China have added a bite to the suggestion that the earliest known gibbons were there about 7 to 8 million years ago, researchers report in October. Journal of Human Evolution..
Those fossils, as well as 14 teeth previously found at the same site and at a nearby site, belong to an ancient species of hylobatids called Yuanmoupithecus xiaoyuansay paleoanthropologist Xueping Ji of the Kunming Museum of Natural History Zoology in China and colleagues. Hylobatids, a family of apes that includes around 20 species of living gibbons and a black-furred gibbon called a siamang, inhabit tropical forests from northeast India to Indonesia.
Ji’s group has assumed that and xiaoyuan it was an ancient gibbon since the species was introduced in a 2006 Chinese publication. But additional fossils were needed to prove that suspicion.
The newly discovered upper jaw piece, found by a local villager and given to Ji during fieldwork a decade ago, contains four teeth, including a partially erupted molar that helped researchers identify it as the remains of a baby who He died before he was 2 years old.
Comparisons with modern apes and ancient primate fossils and xiaoyuan as the oldest known gibbon and questioned a report from two years ago that an approximately 13-million-year-old molar tooth was found in northern India came from a hylobatid, the team says (Serial number: 8/9/20). The fossil found in India, assigned to a species called Kapi ragnagarensisrepresents an extinct group of South Asian primates that were not closely related to modern apes, scientists say.
Previous analyzes of DNA from living primates suggested that hylobatids diverged from other apes in Africa between 22 and 17 million years ago. But it’s a mystery when the gibbons’ ancestors arrived in Eurasia, says paleoanthropologist and study co-author Terry Harrison of New York University. There is a gap in the fossil record of about 10 million years between the estimated time hylobatids arose in or near Africa and the evidence for and xiaoyuan in Asia.
Genetic evidence also indicates that today’s gibbon species shared a common ancestor about 8 million years agowhen and xiaoyuan he was alive. “Could it be that [Y. xiaoyuan] it is the ancestor of all later gibbons,” says Harrison. No, and xiaoyuan he suspected it was closely related to a modern ancestor of the gibbon.
Bumps and depressions on the chewing surfaces and other features of teeth and jaws of and xiaoyuan they closely resemble those of living gibbons, says Ji’s team. Some traits in the fossil species were precursors to slightly different traits in modern gibbons, the researchers suggest.
Based on the size of the molars, they estimate that and xiaoyuan It weighed about six kilograms, similar to today’s gibbons. The molar structure indicates that and xiaoyuan it focused on eating fruit, like most gibbon species today, says Harrison.
Ji’s group “makes a very good case that [Y. xiaoyuan] it is a hylobatid”, says paleoanthropologist David Alba of the Institut Català de Paleontologia Miquel Crusafont in Barcelona.
But the evolutionary state of K. ragnagarensis remains unstable because only one tooth of that species has been found, says Alba, who was not involved in the new study.