Scientists come up with new theory on the origin of primates

January 20th, 2010 - 5:28 pm ICT by ANI  

Washington, January 20 (ANI): A team of scientists has come up with a new theory on the origin of primates, which says that each major primate group has evolved locally from a widespread ancestor on the supercontinent of Pangea about 185 million years ago.

Michael Heads, a Research Associate of the Buffalo Museum of Science, US, arrived at these conclusions by incorporating, for the first time, spatial patterns of primate diversity and distribution as historical evidence for primate evolution.

Models had previously been limited to interpretations of the fossil record and molecular clocks.

“According to prevailing theories, primates are supposed to have originated in a geographically small area (center of origin) from where they dispersed to other regions and continents,” said Heads.

In this new approach to molecular phylogenetics, vicariance, and plate tectonics, Heads shows that the distribution ranges of primates and their nearest relatives, the tree shrews and the flying lemurs, conforms to a pattern that would be expected from their having evolved from a widespread ancestor.

This ancestor could have evolved into the extinct Plesiadapiformes in North America and Eurasia, the primates in central-South America, Africa, India and south East Asia, and the tree shrews and flying lemurs in South East Asia.

Divergence between strepsirrhines (lemurs and lorises) and haplorhines (tarsiers and anthropoids) is correlated with intense volcanic activity on the Lebombo Monocline in Africa about 180 million years ago.

The lemurs of Madagascar diverged from their African relatives with the opening of the Mozambique Channel (160 million years ago), while New and Old World monkeys diverged with the opening of the Atlantic about 120 million years ago.

“This model avoids the confusion created by the center of origin theories and the assumption of a recent origin for major primate groups due to a misrepresentation of the fossil record and molecular clock divergence estimates,” said Heads.

“These models have resulted in all sorts of contradictory centers of origin and imaginary migrations for primates that are biogeographically unnecessary and incompatible with ecological evidence,” he added.

The tectonic model also addresses the otherwise insoluble problem of dispersal theories that enable primates to cross the Atlantic to America, and the Mozambique Channel to Madagascar although they have not been able to cross 25 km from Sulawesi to Moluccan islands and from there travel to New Guinea and Australia.

Heads acknowledged that the phylogenetic relationships of some groups such as tarsiers, are controversial, but the various alternatives do not obscure the patterns of diversity and distribution identified in this study. (ANI)

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