The origin of humans a tale of tangled roots

Dr Daniel Zadik from the Department of Genetics has written an article for his blog examining evidence regarding where humans originated.

In the article he outlines how the discovery of Neanderthals across Europe and Homo erectus in Java resulted in the development of new theories regarding types of 'cave-man' that may have existed in the past and where they would have settled and lived.

Using modern genetic techniques, it is now possible to determine that more differences are found amongst the peoples of Africa than across the rest of the world, which strongly suggests that from an initial population of modern humans in Africa, a relatively small group left the continent to populate the world. But where specifically within Africa did these modern humans originate?

Around 200,000 years ago people appeared who are indistinguishable from today’s. Known as Anatomically Modern Humans (AMH)  they constitute the vast majority of our ancestry. However, while the oldest AMH bones known are from southern and eastern Africa, the continent's acidic soil would mean that many bones would not be preserved.

Thankfully, mitochondrial DNA (or mtDNA), is passed down by mothers and changes slowly only by mutation. These mutations can be used to construct a family tree of mothers and their mothers, going back through time. With every generation, some branches die out when a woman has no children, while the mtDNA on other branches become more common.

Going back far enough all modern mtDNA must descend from one woman, dubbed the “Mitochondrial Eve”. Given that the greatest diversity of branches is found across southern and eastern Africa, this suggests that 'Eve' may have lived there.

Dr Zadik concludes by suggesting that while it is difficult to say for certain where AMH's originated, genetic evidence can at least provide a rough idea - and that investigating the possibilities is part of the joy of genetic research.