Allan Charles Wilson


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(1934–1991) New Zealand biochemist

Born at Ngaruawakia in New Zealand, Wilson was educated at the University of Otago, Dunedin, and at Washington State University before completing his PhD in 1961 at the University of California, Berkeley. After working at the Weizmann Institute in Israel and at universities in Nairobi, Kenya, and Harvard, he returned to Berkeley serving as professor of biochemistry until his death from leukemia in 1991.

In 1967, in collaboration with Vincent Sarich, Wilson, following the work of Emile Zuckerandl, argued that molecular clocks could reveal much about the early history of the human race. Against the opposition of paleontologists they claimed that the divergence between man and the great apes began only 5 million years ago. Their view seems to have prevailed.

In the 1980s Wilson sought to challenge the paleontologists once more, this time on the issue of the emergence of modern humans. While anthropologists favored a date of 1 million years, Wilson's work suggested a time no later than 200,000 years ago.

He chose to work with mitochondria, the cellular organelles which convert food into energy. Like a cell nucleus, mitochondria also contain DNA. It encodes, however, only 37 genes as opposed to the 100,000 of nuclear DNA. Further, mitochondrial DNA evolved rapidly and regularly and, surprisingly, it is inherited from the mother alone. It follows, Wilson pointed out, that “all human mitochondrial DNA must have had an ultimate common female ancestor.” Where and when, he went on to ask, could she be found?

Wilson adopted the parsimony principle that subjects are connected in the simplest possible way. That is, the fewer differences found in mitochondrial DNA, the closer they were connected. Mitochondria from 241 individuals from all continents and races were collected and analyzed. The tree constructed had two branches, both of which led back to Africa.

What was the date of this ‘African Eve’ as she was quickly dubbed by the press? Wilson measured the ratio of mitochondrial DNA divergence between humans to the divergence between humans and chimpanzees. The ratio was found to be 1:25 and, as human and chimpanzee lineages diverged 5 million years ago, human maternal lineages must have separated by 1/25 of this time, namely, 200,000 years ago. Wilson's hypothesis, first presented in 1987, has provoked considerable opposition.

Subjects: Science and Mathematics.

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