The Seven Daughters of Eve
by Bryan Sykes (W. W. Norton & Company, 2001)
(This column was first published in the September 13, 2001 ArtVoice of Buffalo.)
As a birdwatcher, I have for some years been interested in the contribution of genetics to avian systematics. In particular, before he died in 1999, my good friend Charles Sibley made important contributions to these bird interrelationships. For exampl e, he showed that vultures were not at all closely related to hawks as had been assumed in the past but were instead near relatives of storks.
For that reason I was intrigued when I learned that geneticist Bryan Sykes was applying similar analyses to our human relationships. Turning to his second book on this subject,The Seven Daughters of Eve: The Science that Reveals our Genetic Ancestry, I have found wonderful insights into the history of Homo sapiens, or to put it less formally, us.
Here is Sykes' summary of his work through the 1990s: "My research over the intervening decade has shown that almost everyone living in Europe can trace an unbroken genetic link...way back into the remote past, to one of only seven women. These seven w omen are the direct maternal ancestors of virtually all 650 million modern Europeans. As soon as I gave them names -- Ursula, Xenia, Helena, Velda, Tara, Katrine and Jasmine -- they suddenly came to life. This book tells how I came to such an incredible c onclusion and what is known about the lives of these seven women."
Especially with the assignment of these obviously fictitious names to people who lived hundreds of centuries ago, many readers may believe that this analysis belongs in the same category as the kind of nonsense astrologers put forth. That is a misjudgm ent as Sykes science has stood up to extensive scrutiny and replication. Before he undertook this analysis he had already provided solutions through genetic analysis to several long-standing anthropological problems: (1) Identifying the last Russian Tsar and his family members and rejecting Anna Anderson's claim to be the daughter Anastasia; (2) Showing the Asian ancestry of inhabitants of Pacific Islands and rejecting Thor Hyerdahl's theory that they came from South America; and (3) Establishing that the Neanderthal line did indeed die out.
A major contribution of hisSeven Daughters story is his strong condemnation of racial ancestry trees. Here is his take on them: "Perhaps the most serious objectio n to these trees is that their construction demands that the things at the end of the trees, the populations, be objectively defined. This process in itself segregates people into groups in ways that can tend to perpetuate racial classifications. It gives some sort of overall genetic number to something that does not really exist. There are certainly people who live in Japan and Tibet, but there is no genetic meaning to the population of Tibet or Japan, taken as a whole. As this book will sh ow, objectively defined races simply do not exist. Even Arthur Mourant realized that fact nearly fifty years ago, when he wrote: 'Rather does a study of blood groups show a heterogeneity in the proudest nation and support the view that the races of the pr esent day are but temporary integrations in the constant process of...mixing that marks the history of every living species.' The temptation to classify the human species into categories which have no objective basis is an inevitable but regrettable conse quence of the gene frequency system when it is taken too far. For several years the study of human genetics got firmly bogged down in the intellectually pointless (and morally dangerous) morass of constructing ever more detailed classifications of human p opulation groups."
Highly oversimplified, Sykes' lineages are determined by a "molecular clock" whose rarely occurring ticks are mutations in mitochondrical DNA. The more of the resulting DNA differences between two individuals, the farther back their relationship.
Of special interest about the resulting trees is the fact that they trace back through female forebears. This is, of course, quite different from our usual genealogical trees following male lines. Here is Sykes on this: "The common practice of women ad opting the husband's surname on marriage rather than retaining their maiden names makes it very difficult to trace a maternal lineage, for women s names change at every generation. But neither would retention of the maiden name resolve the problem, becaus e a maiden name is, after all, only another surname -- a father's name rather than a husband's. Against this background it is no surprise that it comes as a revelation to many people that there actually is such a thing as a maternal family tree, a mirror image of the traditional paternal version. I have certainly never seen one drawn out.
"Genetics does help to reconstruct detailed maternal trees even within the existing records, but the best solution for future generations of genealogists would be to create a new class of name altogether. Everyone would get this name from his or her mo ther. Women would pass it on to their children. It would be, in effect, an exact mirror image of the present system with its surnames which people get from their fathers and, if they are men, pass on to their children. We would then all have three names: a first name, a surname and a new one, a matriname perhaps. A man passes on his surname to his children; a woman gives her matriname to hers. Since they follow a maternal line of inheritance, these names will closely correspond with mitochondrial D NA. They will also reflect biological relationships more accurately than surnames, because there is only very rarely any doubt about the identity of a child's mother. In time people would be able to recognize their maternal relatives with the same matrina me in just the same way as they can now link up to their paternal family through a shared surname. But until that time comes, if it ever does, reconstructing maternal family trees through written records alone will be much harder than drawing the male equ ivalent."
Based on the genetic differences, Sykes is able to construct European human systematics over the past 45,000 years. And that is where the sisters come in. Originally more formally identified by letters, these older designations are simply assigned by S ykes to female names -- U becoming Ursula, X Xenia, and so on. He then further fleshes out these "daughters of eve' to their approximate time and place and builds quite reasonable stories around them based on anthropoligical evidence about the people of t heir times. For example, he begins his first narrative, "Ursula was born into a world very different from our own. Forty-five thousand years ago it was a lot colder than it is today, and would get colder still in the millennia to come leading up to the Gr eat Ice Age. Ursula was born in a shallow cave cut into the cliffs at the foot of what is now Mount Parnassus, close to what was to become the ancient Greek classical site of Delphi."
Although the book focuses on European forebears, it has much to say about other matters including the heritage of early Americans. Here is what he has to say about their ancestry of Amerinds: "Four mitochondrial clans dominate the genetics of native Am ericans. All four have easily reconstructed and obvious genetic links with people living in Siberia or north-central Asia today. If they went by land, then their route into the Americas can only have been via Alaska. We have enough information about the s ea-level changes over the past hundred thousand years to know that there were two periods when there was a continuous land bridge between Siberia and Alaska. The first bridge was formed fifty thousand years ago and lasted for about twelve thousand years. The second coincided with the last Great Ice Age, when the land was above sea level between twenty-five and thirteen thousand years ago.
"There is a fierce controversy about when America was first colonized. Did the first people arrive across the earlier land bridge or the later one? There are two early archaeological sites in South America which have been used in the past to support th e earlier date....
"Perhaps the greatest evidence against the earlier date for the colonization of the Americas is that one would expect the population, in a land full of game and without prior human occupation, to explode, leaving abundant evidence all over the place. I t is not as if nobody has looked. American archaeologists have worked hard to find it; but without success. However, there is plenty of evidence of a continuous settlement after twelve thousand years ago, with hundreds of sites scattered all across both N orth and South America.
"The genetic evidence from modern native Americans also favours the later crossing. The accumulation of mutations in native Americans within each of the four clans has given all of them ages that fall well within the last thirteen thousand years. Recon structions from modern Siberian and Mongolian patterns show very clearly that the clans were already established and separate from each other well before they reached America. The same applies to the rare fifth clan, that of Xenia, to which about 1 per ce nt of native Americans belong. As we have already seen, that clan had its origins on the borders of Europe and Asia.
"The genetics fits well with the later land crossing from Siberia into western Alaska, just as the Ice Age was waning and the sea levels had begun to rise once again. But getting into Alaska was not the end of the story. Northern America was covered by two huge ice sheets. One enveloped the Rockies and the high mountains of southern Alaska; the other covered the whole of Canada. At the height of the last Ice Age, when sea levels were low enough to expose the land bridge from Siberia, these two great ic e sheets fused to seal off access to the interior. The first Americans were faced with a dilemma. If it was cold enough to cross into Alaska by land, it was also too cold to get past the ice sheets on the other side. Alternatively, if it was warm enough t o get through the ice sheets, by then the land bridge would be flooded. There had to be a period when the first Americans were stranded in western Alaska. Eventually the two ice sheets withdrew sufficiently to create a narrow corridor between them. This w as no verdant valley, but a harsh passage though which the pioneers advanced little by little. At last the corridor opened out into the rich expanses of the Great Plains which were teeming with game. It must have been a wonderful and welcome sight to thos e first pioneers who had struggled through the ice corridor."
We have heard a great deal lately about the human genome and the race to record it and also about the use of genetic "fingerprinting" in criminal cases. Here is a book describing a quite different line of research which I believe is still more interest ing. And Sykes does an excellent job in communicating science to the lay reader; I know of few who do as well.-- Gerry Rising