|Daughters of Eve
By Jennifer Viegas
April 21 — It may be the world’s largest known family tree.
Researchers from Oxford University in Oxford, England, have identified seven ancestral matriarchal groups from which all Europeans appear to be descended. These maternal clans form the root of a family tree that has sprouted millions of individuals.
Every European, according to the study, can trace his or her evolutionary history back to the seven ancestral mother groups, also referred to as the Seven Daughters of Eve.
The researchers, who both
discovered and formulated the genetic groupings, say these women would
have lived between 8,000 to 45,000 years ago.
Hamsters Inspired Theory
Bryan Sykes, professor of human genetics at Oxford University, first suspected Europeans could have common lineages when he was a young boy. His inspiration came from a news story he read that stated all hamsters in the world came from one pregnant female found in the Syrian desert in 1930.
Time passed, but he remembered the hamsters. In recent years, he tested out the hamster idea by identifying and ordering the individual components of DNA taken from the droppings of several of these rodents.
He discovered that one specific kind of genetic material, mitochondrial DNA, appeared to be identical among all of the hamsters. This kind of DNA can only be passed down from a mother to her children.
Men have mtDNA in their sperm, but a
chemical marks it for destruction during the fertilization process.
Therefore, the hamster study findings prompted Sykes to add matriarchal
clans to his developing theory about common lineages.
Unlike hamsters, which share one type of mtDNA, the human test subjects’ DNA clearly fit into seven distinct groups: the seven daughters on the European family tree. The “daughters” notion is more figurative than literal, as it broadly refers to seven matriarchal genetic groups, rather than to seven individual women.
Leonardo Salviati, a post doctoral researcher at Columbia University who specializes in mitochondrial DNA studies, says Sykes’ theory “is plausible.”
“Mitochondrial DNA allows us to trace human evolution,” says Salviati. “DNA mutates at a very slow rate, so if you can accumulate mutations and categorize them in specific groups, you can draw direct ancestral lineages.”
Mutations in this kind of DNA occur in humans about every 10,000 years. Sykes, therefore, is able to guess when each of the seven female genetic lines first appeared in Europe.
The earliest suspected arrival date, 45,000
years ago, corresponds with the appearance of modern human remains in
fossil records. But this date is thousands of years ahead of when
anthropologists previously thought migrants arrived in Europe.
Links to African Eve
Further, all seven of the genetic groups appear to be descended from the “Lara” clan, one of three clans that still exist today in Africa. This supports the African Eve theory, proposed in the late ’80s by biochemist Allan Wilson, Mark Stoneking and others, which states that all humans share a common African ancestor. Wilson and his colleagues used the same genetic material, mtDNA, for their study.
Terry Melton, president of Mitotyping Technologies, a firm specializing in mtDNA forensic studies, says, “[Sykes] presents a great idea, but the system is not perfect. A consensus may be derived by formulating haplogroups [gene groups], but it would be impossible to do this with 100 percent accuracy.”
Melton explains that some parts of the mtDNA
mutate faster than others, so additional variation could appear within
the seven daughter groups.
What About Americans?
Americans of European heritage may fit into one of the seven categories. But different genetic groups based upon mtDNA variations likely exist for those without European ancestors.
Native Americans, for example, appear to have descended from Asians who migrated to the Americas sometime between 30,000 and 3000 BC. Melton says they seem to have limited mtDNA variations, meaning that they probably descended from just a few Asian lineages.
In future, Sykes hopes to map out genetic
groups for other continents, to perhaps find out more about the mothers
to us all.