5 August, 2013 – 12:54 april holloway
A new study published in the journal Science has revealed that almost every man alive today can trace his origins to one man who lived approximately 135,000 years ago, and that this ancient man was alive at the same time as the woman who his known as the ‘mother of all women’, providing evidence for an ancient ‘Adam and Eve’.
The research team obtained their results by undertaking the most comprehensive study to date on the male sex chromosome. The Y chromosome is passed down identically from father to son, so mutations in the chromosome can be used to trace back the male line to the father of all humans. The study involved sequencing the entire genome of the Y chromosome for 69 men from seven global populations. By assuming a mutation rate linked to archaeological events (such as the migration of people), the team concluded that all males in their global sample shared a single male ancestor in Africa roughly 125,000 to 156,000 years ago. This challenges previous research which suggested that men’s most recent common ancestor lived just 50,000 to 60,000 years ago.
But before jumping to any conclusions, it must be pointed out that a separate study in the same issue of the journal Science found that men shared a common ancestor between 180,000 to 200,000 years ago, and yet another study back in March in the American Journal of Human Genetics, showed that several men in Africa have unique, divergent Y chromosomes that trace back to an even more ancient man who lived between 237,000 and 581,000 years ago. The variations in results are due to the fact that gene studies always rely on a sample of DNA, which can never provide a complete picture of human history. Different DNA samples lead to different estimates of how old our common ancestors really are and only further analyses will help to pinpoint a more precise date range.
A similar analysis has also been conducted to trace back a common ancestor of all women, known as ‘mitochondrial Eve’. The DNA from mitochondria, the energy centre of a cell, is carried inside a female’s egg, so only women pass it on to their children. The DNA held inside mitochondria can therefore reveal the maternal lineage to ancient Eve, who is believed to have lived in Africa between 99,000 and 148,000 years ago – almost the same time period during which the Y chromosome ‘Adam’ lived.