Apes and monkeys split along different evolutionary paths long ago - that much has been known for a long time, due to genetic markers in our respective DNA. A new discovery in Tanzania may help scientists pinpoint when the genetic family tree that includes monkeys diverged from the one that includes apes and humans.
Two fossils, each 25 million years old, were recently found in the Rukwa Rift basin in southwestern Tanzania. These artifacts suggested apes and monkeys were already differentiated at that time. This is in line with the 25-30 million year-old time frame suggested by DNA, and five million years older than the oldest such fossils previously known.
The two bone fragments that are helping to shed light on this evolutionary puzzle are a jaw bone from a newly-discovered species of ape called Rukwapithecus Fleaglei, and a tooth from a primate, Nsungwepithecus gunnelli. These two represent some of the oldest-known primates, the group that includes apes and humans, and cercopithecoids, like macaques and baboons.
The new findings, published online this week by Nature, suggest that the two groups were separate even at that time. Although the discovery of these fossils does not accurately date when the two forms of primate separated, it does push back the window when the split occurred. The oldest pairs of fossils known from both groups before this time were only 20 million years old. These fossils, from the Oligocene epoch, set back the latest possible point when the two evolutionary lines split by five million years.
Nancy Stevens, the associate professor of palentology from Ohio University who lead the team which made the discovery stated "The late Oligocene is among the least-sampled intervals in primate evolutionary history."
The location of the finds also played a critical role in being able to date the fossils, as they were found in an area where the minerals around them could be accurately dated. The same location has also previously yielded other finds as well, revealing the ages of those finds.
Lead geologist Eric Roberts of Australia's James Cook University said "The rift setting provides an advantage in that it preserves datable materials together with these important primate fossils."
The fossils were analyzed using a MicroCT scanner, which created 3D images that could easily be compared to specimens from other species.
