Roll back the clock

One way of working out how far back the human line goes is to use the 'Mitochondrial Clock'.

Mitochondria are like the engine of the cell - they supply the energy to help the cell do what it needs to do. But what's handy is that these little boiler houses have their very own package of DNA (separate from that found within the nucleus of the cell).  Rather being a mix of both parent's DNA - like in the nuclear version - the package found in Mitochondria comes entirely from the mother.  That keeps things nice and simple.

As time goes on that DNA mutates a little and on average it mutates at a predictable rate.  So if you take a group of modern day people and see how different their mitochondrial DNA is, then it's possible to trace how far back it would have been that those people had the same DNA pattern - what's dubbed as Mitochondrial Eve.

Well a new piece of work has looked at the accuracy of this method and calibrated it. The researchers worked out that humans dispersed from a small population around 55-70 000 years ago (Soares et al, American journal of Human Genetics 2009).  As part of their study they ran checks against known points in recent history where human populations have resettled, and these used these to verify their findings. What this means is that the group being tested shared an ancestor in a small group of human beings all that time ago.

This is way before Adam and Eve walked the Garden of Eden and together with other evidence illustrates that the human lineage extends a long, long way. I discuss the Biblical for this here