"Archicebus is a quite odd creature," lead author Xijun Ni of the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences, told Discovery News. "It has many features that support its tarsiform (like tarsiers) affinity, but also has many features typically seen in anthropoids."
It had the feet of a small monkey, but the arms, legs, skull and teeth of a very primitive primate. The researchers were surprised that it had such small eyes. Modern tarsiers have some of the largest eyes, relative to body size, in the animal kingdom. They allow the tiny primates to see well at night.
Although Archicebus hailed from Asia, the earliest known humans came from Africa.
"This suggests that a primitive anthropoid colonized Africa from Asia, and from these early African anthropoids all later catarrhines (monkeys, apes and humans) evolved," Gebo said.
As for the small size of Archicebus, other mammal lineages often started small and evolved to be bigger over time. The phenomenon is known as "Cope's Rule." No one is entirely sure why this happened among mammals, but the environment must have only supported such a size in terms of climate, food sources and other factors.
Eric Delson is a paleoanthropologist at Lehman College. When sent the study, Delson told Discovery News, "Archicebus is a fantastic new fossil, which preserves more details of its anatomy than anything of a similar age."
Delson expects more very early primates to be found in Asia, particularly in central China.
He said, "It seems likely that when more sites a bit older than this are found in eastern and southern Asia, they might provide hints about the origin and last common ancestor of extant primates."