by Jane Harris Zsovan

Forget Botox. The hottest babe around is at least 150,000 years old, and looking good, all things considered. She's mitochondrial Eve, of course, believed by some to be the mother of all living humans.

Her many defenders, including Bryan Sykes, author of the Seven Sisters of Eve, have turned the mother of all grannies into a pop culture icon - and a poster granny for anti-racism. But, however worthy the cause, we must how much is fact and how much fiction. All the more so if the cause is worthy.

African Eve's claim to fame

Eve's proponents say that our mitochondrial DNA is passed down only through the maternal line. And if you go back far enough, every living human being is her descendant. In other words, while other women lived alongside and before her, she is the only woman fruitful enough to have succeeded in passing her mitochondrial DNA down to every human being alive today.

But here's a problem we need to consider: If paternal MtDNA is also inherited in humans, as it has been demonstrated to be in sheep, then it may not accurately reflect our maternal inheritance. And, if that’s the case, we can't be sure that everyone's most common recent female ancestor lived in Africa. That doesn't mean that the Out of Africa hypothesis is incorrect. Rather, we must ask, is MtDNA analysis sure enough to support the hypothesis?

If not African Eve, who?

African Eve has always had her disbelievers in the field of human evolution. As John Noble Wilford explained in "Critics batter proof of an African Eve" (New York Times, May 19, 1992),

No one is disputing the considerable evidence showing that the earliest prehuman ancestors branched off from chimpanzees and gorillas in Africa 5 million to 10 million years ago. The ancestral species Homo erectus began migrating to Asia and Europe more than one million years ago, which could be within the time frame for the mitochondrial DNA results, depending on assumptions of mutation rates.

Then, as Dr. Wolpoff has argued, modern Homo sapiens could have evolved from these ancient ancestors independently in many parts of the world. Dr. Wolpoff and Dr. Alan Thorne, an anthropologist at the Australian National University in Canberra, have reported that paleontologists are finding at widely separated sites important similarities between the skulls of ancient humans and their modern counterparts, similarities that they said were "hard to square with a theory based on African migration and mass replacement."

This alternative view of human evolution argues that "modern humans evolved everywhere, as populations mixed and advantageous genes spread." (National Geographic News, January 11, 2001).

The scientists who take this latter view (multiregionalists) are not saying that different groups of humans have separate ancestors. Rather, they are saying that all modern humans descend from more or less the same ancestors, but scattered in different regions, rather than from a single woman in Africa.

Many human evolutionists are attached to African Eve because she eliminates otherwise troubling questions. For example, if the multiregionalists are correct, modern humans appear quite suddenly in a number of different places, and a cause must be sought. But if there really is an African Eve, the evolutionist can simply assume that she was healthier and more fertile than other women.

As Friderun Ankel-Simons and Jim M. Cummins point out, it's not surprising that Eve’s supporters have been reluctant to consider evidence that casts doubt on her existence: “Regardless of whether the African Eve Hypothesis is correct or not, it cannot be supported by the assumption of strictly matrilineal mtDNA evolution.”

Textbooks, blogs, and popular authors can still sometimes be heard to insist that there is no paternal contribution to mitochondrial DNA, perhaps based on old information. For example, in his widely read 1986 book,The Blind Watchmaker, Richard Dawkins has stated that the sperm contain no mitochondria:

All the mitochondria in you are descended from the small population of mitochondria that travelled from your mother in her egg. Sperms are too small to contain mitochondria, so mitochondria travel exclusively down the female line, and male bodies are dead ends as far as the mitochondria is concerned. Incidentally, this means that we can use mitochondria to trace our ancestry, strictly down the female line. (p. 176)

He amended this "dead-end" assessment slightly in his 1995 book River Out of Eden, A Darwinian View of Life:

Sperms are too small to contain more than a few mitochondria... these mitochondria are cast away with the tail when the sperm head is absorbed in the egg fertilization.

Actually, as we have seen, some sperm mitochondria do enter the egg and we do not know the size of the influence they have. The fact that there are only a few of them may or may not be decisive.

So was there an African Eve? Perhaps but, despite progress, we do not really know very much about our origins yet. It is perhaps a bit like trying to predict the picture represented by a 5,000 piece puzzle - where we do not have the picture on the box - after discovering a few matching pieces in various places. We are influenced not only by what we see in the few pieces filled in but by what we want or expect to see in the vastly greater blank spaces.

Back to Part One: Our Mitochondria: A piece in the puzzle of our origins?

Back to Part Two: What Does Our Mitochondrial DNA Say About Human Ancestry?

Resources for series

Ankel-Simons, F., and J. M. Cummins. 1996. "Misconceptions about mitochondria and mammalian fertilization: Implications for theories on human evolution." Proceedings of the National Academy of Sciences USA 93 (1996): 13859-13863.

Cummins, J. M. 2001. Cytoplasmic Inheritance and Its Implications for Animal Biotechnology. Theriogenology 55: 1381-1399.

Sutovsky, P. and G. Schatten. 2000. "Paternal Contributions to the Mammalian Zygote" Fertilization After Sperm-Egg Fusion." International Review of Cytology 195: 1-65.

Yanagimachi, R. 2005. "Male Gamete Contributions to the Embryo." Annals of the New York Academy of Sciences 1061: 203-207.

Crozet, N., M. Dahirel, and P. Chesne. 2000. "Centrosome Inheritance in Sheep Zygotes: Centrioles Are Contributed by the Sperm." Microscopy Research and Technique 49: 445-450.

Klotz, C., M.-C. Dabauvalle, M. Paintrand, T. Weber, M. Bornens, and E. Karsenti. 1990. "Parthenogenesis in Xenopus Eggs Requires Centrosomal Integrity." Journal of Cell Biology 110: 405-415.

Palermo, G. D., S. Munne, and J. Cohen. 1994. "The Human Zygote Inherits Its Mitotic Potential from the Male Gamete." Human Reproduction 9: 1220-1225.

Palermo, G. D., L. T. Colombero, and Z. Rosenwaks. 1997. "The human sperm centrosome is responsible for normal syngamy and early embryonic development." Reviews of Reproduction 2: 19-27.