The marvel of modern population genetics tells us that the human race originated in Africa and lived there in isolation for 150,000 years. Those who remained are the ancestors of most of the one billion people who live in Africa today. About 60,000 years ago a small group of about 1,000 to 2,500 people left the continent for unknown reasons, and it is this remarkably small group of people who become the ancestors of everyone else in the world.
This is but one of the many intriguing details that populate this well-structured book on ancestral science by Christine Kenneally, an award-winning Australian journalist and PhD linguist who became intrigued with genetics and genealogy during her search for information about her unknown grandfather.
The result is a text that not only explores the power of modern genetics but also chronicles the use and misuse of genealogical information.
Genealogy
Over half of the book is focused on the development, growth, and applications of the increasingly sophisticated systems that can be used to probe one's family tree. We learn of http://Ancestry.com with its 12 billion family records, http://FindMyPast.com, and the massive Mormon data base that is 32 times the size of the data in the Library of Congress. Genealogy studies, as the author points out, go back to the bible with its "Abraham begat Isaac" etc.
Genealogy surged in popularity with the European aristocracy and grew with the public's fascination with possible personal connections to famous and infamous personalities. Kenneally also tells of the dark side of genealogy, with its roots in eugenics, Nazism, and its application of class against class.
She is candid about the controversies surrounding the field and the skepticism with which it is held by many scientists. To some it has "the real world verifiability of astrology"-a field occupied by "dilettante hobbyists." She quotes Richard Lewontin, the famous Harvard biologist: "Why do we feel pride (or shame) for the action of others over whom we have no influence?"
The book, however, also takes a more humanistic view and provides examples of more positive aspects of tracing one's lineage. Kenneally gets at the heart of genealogy's emotional appeal with the analogy "then we probably should not feel any satisfaction when our favorite football team wins a game-Perhaps genealogy is no more complicated than the impulse to cheer for the home team," she writes.
The book examines the origins of the eugenics movement and links it with the xenophobia of the 1880s, the distortions of Darwin's theories, and the writings of an American, Madison Grant, who in 1916 penned The Passing of the Great Race, which Hitler's doctor, Karl Brandt, used as a defense at the Nuremburg trials. In Kenneally's view, eugenics was not a science but simply a ruse used 'to give long-standing social divisions a scientific rationale."
But genealogy, Kenneally concludes, has value when it illuminates stories of populations whose past has been distorted by a biased historical record. She illustrates this with persuasive narratives of African-Americans, Jews, Australian convicts, and orphans.
She says she also believes that culture can contribute to enduring changes in human behavior and sites the work of Nathan Nunn and Leonard Wantchekon, who linked the loss of community trust brought about by the slave trade in the 19th century to the persistent disruption of the economy and lives in Africa a century later. This view is provocative but seems less than compelling. To her credit, she adds a note of skepticism: "No one is suggesting that lives of ancestors can be examined like a fortune-teller's deck. Correlation is not Causation."
Modern Genetics
The latter part of the book is devoted to the impact of modern genetics. Critical are the realizations that the Y chromosome is passed from father to son intact and that microsomal DNA is passed on only from the mother. That coupled with modern high-throughput genomics is accelerating our knowledge about ourselves at a breakneck pace.
For example, we now know that large populations of what was once the Mongolian Empire harbor the Y chromosome from Genghis Khan. Population genetics studies have uncovered the genetic origins of the British people. Science has established the presence of Neanderthal genes in almost all of us, along with genes from Denisovans, a pre-human race discovered only in 2010. Some of us no-doubt harbor genes from a yet-unidentified race.
But for individuals, modern genetics may not be so revealing. Going back 10 generations, we have 1,024 ancestors in that generation alone and the genetic contribution of each is minuscule. Indeed over successive generations much genetic information is lost and we are in "the odd position of being biologically unrelated to many of our blood relatives," she writes.
While many of us would like to take some pleasure from finding we are related to Joan of Arc, Christopher Columbus, or William Shakespeare, genetically it's not meaningful. By 16 generations back, we have 65,336 ancestors, and most have contributed little or nothing to us genetically. Furthermore, our DNA doesn't tell us "what a person will look like, think like, or live like. They are records only of our ancestors; they tell us what once existed."
DNA
The book also discusses the contribution of DNA to our understanding of race. DNA studies reveal that the concept of race is a myth. Simply put, the ways we differ from one another across racial or ethnic divides are far smaller than everything we have in common.
However, simply saying that race doesn't exist doesn't appear to be rapidly changing people's minds. None the less, modern genetics has made us aware of just how much racial mixing has gone on throughout history.
Personal Genome Data
The book closes with candid discussions of what personal genome data actually reveal. Both the author and her husband had them done. Most of the information found, she says, was not illuminating or particularly informative. Her husband, worried about a family history of multiple sclerosis, was told that he was "less likely than the average person to develop MS."
Why then does Kenneally, elsewhere in the book, seem surprised that doctors often don't look at this data when dealing with patients? She seems to answer her own question, commenting that 21st century genetics is not as determinative as we had hoped or feared: "Your genome is just the first hand that life deals you. How you play it is up to you."
2014, VIKING, ISBN 0670025550; AVAILABLE IN HARDCOVER, PAPERBACK, KINDLE, AND AUDIO EDITIONS
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