In 1987, a trio of University of California at Berkeley biochemists, led by the late Allan Wilson, captured worldwide attention by saying that they had found the biological “Eve.” The researchers used small bodies in the cell called mitochondria that are the source of the cell’s energy. These were chosen because they are small, consisting of 37 genes, are passed between generations by the female, and remain unchanged except for small mutations that occur at a constant rate.

Wilson’s group tested 147 individuals from five geographical regions and, using the accepted mutation rate of 2 percent to 4 percent per million years, concluded that the common ancestor of all of today’s mitochondria types lived in Africa 140,000 to 200,000 years ago. Wilson was quick to point out that Eve “wasn’t the literal mother of us all, just the female from whom all our mitochondrial DNA derives. Other females contributed to the nuclear gene pool.”

This fine distinction was lost on the popular press, however, with the following typical report: “A woman who lived in southern Africa about 200,000 years ago has become known as ‘Eve’ and is the mother of us all.” The Eve hypothesis survived many critics over the years, with a note in the Oct. 8, 1999, issue of Science saying she has been traced to a Khoisan bushwoman in Botswana some 120,000 years ago.

If there was an “Eve,” it follows there should be an “Adam,” and a report in the Jan. 25, 1991, issue of Science gives credit for his discovery to Gerard Lucotte of the College of France in Paris. He made a study of the male Y-chromosome, which also remains largely unchanged between generations except for a measurable mutation rate in a small portion of one arm. Lucotte studied five different population types ranging from native French to African pygmies. Tracing the mutation backward in time and region, Lucotte placed “Adam” as an Aka pygmy in what is now the Central African Republic and having lived 200,000 years ago.

As in the case of Eve, several subsequent genetic studies have been done on Adam, with one in the Oct. 31, 1997, issue of Science giving the results from two research groups from Stanford University and the University of Arizona. Both indicated that Adam was a southern African living 100,000 to 200,000 years ago.

It would seem logical that, if a biological Adam and Eve did exist, they would have lived at the same time. The initial dates given for Adam seem to bear this out, overlapping as they do, with the date given for Eve.

But now Peter Oefner and Peter Underhill, members of the Stanford University group mentioned, have revised the date for Adam drastically downward. After analyzing the Y-chromosome of more than 1,000 men from 21 regions of the world, they have come to the conclusion that Adam existed 70,000 to 50,000 years ago. This would have been far too late for him to have had any kind of liaison with Eve, who is still dated to 140,000 years ago.

In an article in the Nov. 4, 2000, issue of New Scientist, Oefner said he was surprised by “the striking differences” in the ages of mitochondrial DNA and the Y-chromosome. Underhill offered a number of explanations in a Nov. 15 report by Maggie Fox from Reuters. Women were good at passing on their genes, says Underhill, while men hit a genetic bottleneck about 50,000 years ago that allowed one Y-chromosome to become dominant. Among the possibilities is one tribe becoming dominant and claiming women from groups they conquered, polygamy, or large numbers of males producing all daughters.

Whatever the reason, Eve’s mitochondria were widespread when the Adam Y-chromosome became dominant. Oefner says the results actually emphasize the closeness of all humanity and the fact that “we are all sitting in the same boat.”

In a paper to be published in the next issue of Science, Milford Wolpoff of the University of Michigan disputes the Eve hypothesis altogether. He made a study of the skulls of extinct “archaic” humans, such as Neanderthals, and those of early humans who are the ancestors of modern humanity. He said that cranial differences in extinct species should be greater than for groups that were ancestors to humanity today. Instead the differences were the same for both groups, leading Wolpoff to say that Eve never existed but we stem from the mating of early migrating humans, with local archaics spreading a mixture of genes worldwide. And so the debate goes on.

Clair Wood taught chemistry and physics for more than 10 years at Eastern Maine Technical College in Bangor.