- The Seven Daughters of Eve: The Astonishing Story that Reveals How Each of Us Can Trace Our Genetic Ancestors by Bryan Sykes
Corgi, 368 pp, £6.99, May 2002, ISBN 0 552 14876 8
- Mapping Human History: Unravelling the Mystery of Adam and Eve by Steve Olson
Bloomsbury, 293 pp, £7.99, July 2003, ISBN 0 7475 6174 5
- The Journey of Man: A Genetic Odyssey by Spencer Wells
Penguin, 224 pp, £8.99, May 2003, ISBN 0 14 100832 6
Until recently, the study of human prehistory relied on the material collected by archaeologists and palaeontologists. Bones, stones and pottery are not the only evidence now available to prehistorians, however: the DNA of living humans contains a record of the DNA of their ancestors. Molecular genetic techniques, developed originally in medical, agricultural and industrial research, have been seized on by scientists interested in the history of our species, and have led to spectacular advances in our understanding of human evolutionary history.
Before discussing these three popular accounts of how DNA techniques can be used to study human ancestry, I should declare an interest: I was a postdoctoral research associate in Bryan Sykes’s Oxford laboratory in the late 1980s. When I joined it in 1987, his team was working on inherited conditions such as osteogenesis imperfecta, or brittle bone disease, but my project was an attempt to recover DNA from archaeological bones, something that had not previously been achieved.
Those were exciting days. Earlier in 1987, a group of US scientists had published a paper in Nature, now considered a classic, entitled ‘Mitochondrial DNA and Human Evolution’. Mitochondrial DNA is an ideal tool for the study of evolution because it is inherited only through the maternal line, usually unchanged except for the genetic mutations that occur over time. This means it can be used to trace maternal lineages through many generations. In contrast to the bulk of the DNA carried in our cells, mitochondrial DNA is relatively uncomplicated and easy to study. The authors of the Nature report had studied the mitochondrial DNA of living people and concluded that we are all descended from a common African female ancestor, whom they called ‘Mitochondrial Eve’, or ‘African Eve’. The idea that the whole human race might have a single ancestral mother captured everyone’s imagination. Eve featured topless on the cover of Newsweek.
In the years that followed, scientists generated thousands of mitochondrial DNA sequences and used them to build phylogenetic (or family) trees, to elucidate the history of human populations. The interpretation of the data spawned an ancillary industry of mathematicians and statisticians to help classify and organise the sequences, and a pattern has gradually emerged. For example, Native American mitochondrial DNA types fall into four haplogroups (groups of similar sequences), identified by the letters A, B, C and D, which can be traced back to Asia. Polynesians, who also originated in Asia, were found to belong to mitochondrial haplogroup B. Many sub-Saharan peoples fall into subgroups of a haplogroup given the letter L.
In 1996, Martin Richards at Oxford and several other scientists, including the mathematician Hans-Jürgen Bandelt and Bryan Sykes, concluded that most of the mitochondrial DNA types of living Europeans fall into several major haplogroups, eventually named H, J, K, T, U, V and X. The paper in which they published their conclusions caused controversy because their estimated dates for the origin of the groups were at odds with accepted models of the prehistoric settlement of Europe. Later studies by Richards and his colleagues revised the nomenclature and age of the groups, and warned of the difficulties of classifying and dating mitochondrial sequences.
In The Seven Daughters of Eve Bryan Sykes fleshes out these classificatory schemes and age estimates. He gives the haplogroups names – Helena (Greek for ‘light’), Jasmine (Persian for ‘flower’), Katrine (Greek, ‘pure’), Tara (Gaelic, ‘rock’), Ursula (Latin, ‘she-bear’), Velda (Norse, ‘ruler’), and Xenia (Greek, ‘hospitable’) – and writes about them as the ‘mothers’ of all Europeans, supplying each one with a biography. Tara, for example, Sykes’s own ancestral mother, lived with her brother in a band of hunters in the depths of the last Ice Age.