Known as "Ida," the nearly complete transitional fossil is 20 times older than most fossils that provide evidence for human evolution.
It shows characteristics from the very primitive non-human evolutionary line (prosimians, such as lemurs), but is more related to the human evolutionary line (anthropoids, such as monkeys, apes and humans), said Norwegian paleontologist Jørn Hurum of University of Oslo Natural History Museum. However, she is not really an anthropoid either, he said.
The fossil, called Darwinius masillae and said to be a female, provides the most complete understanding of the paleobiology of any primate so far discovered from the Eocene Epoch, Hurum said. An analysis of the fossil mammal is detailed today in the journal PLoS ONE.
"This is the first link to all humans ... truly a fossil that links world heritage," Hurum said.
Some are not convinced:"
On the whole I think the evidence is less than convincing," said Chris Gilbert, a paleoanthropologist at Yale University. "They make an intriguing argument but I would definitely say that the consensus is not in favor of the hypothesis they're proposing."The nifty thing is that this is an almost complete skeleton at a time when all we have is scattered jaw bones, long bone fragments and teeth to try to identify these critters. Whether or not the authors of the paper are overreaching, this is a sensational find.
The Ida team points to the fact that some of the fossil's teeth, toe and ankle bones resemble anthropoids more than modern lemurs. But other researchers point out that primitive lemurs, as opposed to modern lemurs, also share many of these features.
"They claim in the paper that by examining the anatomy of adapids, these animals have something to do with the direct line of human ancestry and living monkeys and apes. This claim is buttressed with almost no evidence," said paleontologist Richard Kay of Duke University. "And they failed to cite a body of literature that's been going on since at least 1984 that presents evidence against their hypothesis."
Kay said the researchers did not compare Ida to other important fossil primates from this time, especially those from a group called Eosimiads, that could contradict their claims.