Wednesday, 1 June 2005
This small, underdeveloped fossil tooth from Pakistan indicates the primate it came from once ate insects and fruit, scientists say (Image: PNAS/CNRS)
Three newly discovered primate species that lived 30 million years ago suggest that our ancestors originated in Asia not Africa, challenging the well-known "Out of Africa" theory of human evolution.
But it could be something a bit more complicated, such as "Out of Asia into Africa and Back to Asia", since some researchers now think Asian primates journeyed to Africa, where they evolved into humans, who then travelled both in and out of Africa.
According to a study published in the latest Proceedings of the National Academy of Sciences, numerous fossil teeth found in the Bugti Hills of central Pakistan were from three new anthropoids.
Anthropoids are the group scientists believe were our world-travelling animal cousins, the primates from which humans evolved.
"The Oligocene period [30 to 25 million years ago] in south Asia was so far totally undocumented palaeontologically," says lead author Dr Laurent Marivaux.
"So, it is not surprising that the discovery of fossilised animals from this period is totally new for science, and that they [may] change or modify substantially our previous view on mammal evolution, notably here, the evolutionary history of anthropoid primates.
"The evolutionary history of these old anthropoid lineages represents the beginnings of the evolutionary history of humans."
Marivaux and his team named the new anthropoids Bugtipithecus inexpectans, Phileosimias kamali and Phileosimias brahuiorum. They were tiny and somewhat similar to today's lemurs, says Marivaux, a palaeontologist at the Institute of Evolutionary Science at Montpellier II University in France.
Their small, underdeveloped teeth reveal the primates probably ate insects and fruit. Climate records for this period suggest that the animals lived in a warm, humid tropical rainforest.
Fossil remains for other animals indicate the primates shared the Asian rainforest with more than 20 different species of rodents, bats, carnivores, deer-like animals, pigs, a rhino-like creature, called baluchitherium, and other primates.
Remains for later primates similar to the new anthropoids have previously been found in China, Burma and Thailand. The newly excavated teeth now indicate that anthropoids had a larger range in Asia than thought, since the animals made their way to Pakistan.
Dr Christopher Beard, curator and head of the Section of Vertebrate Paleontology at the Carnegie Museum of Natural History in Pittsburgh, says he generally agrees with the new conclusions.
"Together, the fossil anthropoid primates that are known from China, Thailand, Myanmar and now Pakistan constitute an impressive amount of data indicating that the 'higher primate' lineage that today includes all monkeys, apes, and humans must have originated in Asia, not in Africa as earlier scientists believed," Beard says.
"[The new evidence indicates] early members of this [anthropoid Asian group] made its way to Africa, where they continued to evolve and diversify, eventually giving rise to living monkeys, apes and humans."
Christopher Wills, professor of biological sciences at the University of California, San Diego, agrees it was likely that early anthropoid evolution did not just occur in Africa.
Wills says the evolution probably included "substantial migrations over long distances, in and out of Africa perhaps".
Beard and Marivaux say the early anthropoids that stayed in Asia continued to evolve too, but not in a direction that led to apes and humans.
Most experts say humans only emerged in Africa.