Experts suggest ancient fossils ‘not human ancestors but extinct cousins’

Thursday, February 17, 2011

LONDON - Biological anthropologists from the George Washington University and the New York University have questioned the claims that several prominent fossil discoveries made in the last decade are our human ancestors.

Instead, they offered a more nuanced explanation of the fossils’ place in the tree of life.

They concluded that instead of being our ancestors the fossils more likely belonged to extinct distant cousins.

“To simply assume that anything found in that time range has to be a human ancestor is naive,” said study co-author Bernard Wood, Professor of Human Origins and professor of Human Evolution Anatomy at GW.

The study reconsiders the evolutionary relationships of fossils named Orrorin, Sahelanthropus and Ardipithecus, dating from four to seven million years ago, which have been claimed to be the earliest human ancestors.

Ardipithecus, commonly known as ‘Ardi’, was discovered in Ethiopia and was found to be radically different from what many researchers had expected for an early human ancestor.

Nonetheless, the scientists who made the discovery were adamant it is a human ancestor.

“We are not saying that these fossils are definitively not early human ancestors,” said co-author Terry Harrison, a professor in NYU’s Department of Anthropology.

“But their status has been presumed rather than adequately demonstrated, and there are a number of alternative interpretations that are possible,” he added.

The authors are sceptical about the interpretation of the discoveries and advocate a more nuanced approach to classifying the fossils.

Wood and Harrison argued that it is naive to assume that all fossils are the ancestors of creatures alive today and also noted that shared morphology or homoplasy - the same characteristics seen in species of different ancestry - was not taken into account by the scientists who found and described the fossils.

They suggested there were a number of potential interpretations of these fossils and that being a human ancestor was by no means the simplest, or most parsimonious explanation.

Wood and Harrison cautioned that history has shown how uncritical reliance on a few similarities between fossil apes and humans can lead to incorrect assumptions about evolutionary relationships.

They pointed out the cases of the Ramapithecus discovery in south Asia, which was touted in the 1960s and ’70s as a human ancestor, and Oreopithecus bambolii discovered in Italy, which was assumed to be a human ancestor because of some of its skeletal features.

After more detailed research was done on both of them, both were found to be fossil apes instead.

The study will be published in the upcoming issue of the journal Nature. (ANI)

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