[Nathan Rossman]

Nathan Rossman  asked the Naked Scientists:

Hi Chris,

I really enjoy listening to the programme and hope you keep posting them online for me to download.  

My question is:

I am familiar with the science of genetics from an entry-level perspective. I've recently read the book entitled "The Seven Daughters of Eve" by a guy called Bryan Sykes.

In the book he has states that using mitochondrial DNA he has traced all of the living people on Earth today back to, I think it was, 31 common maternal ancestors.

What is the limit to how far we can go back into the past with this DNA? I'm sure much has been published since the book was published in 2003. Anyway, my question it, could Mitochondrial DNA be used to go back across species boundaries, far enough back to a Cro-Magnon or early hominid?  

Thanks, keep up the good work!  

Nathan Rossman
University of Missouri-Columbia

What do you think?

[RD]

Stefan Lovgren
for National Geographic News
August 31, 2005

Scientists have sequenced the genome of the chimpanzee and found that humans are 96 percent similar to the great ape species...

The number of genetic differences between humans and chimps is ten times smaller than that between mice and rats.

http://news.nationalgeographic.com/news/2005/08/0831_050831_chimp_genes.html

[blakestyger]

This is a very interesting question.
Mitochondrial Eve is a concept only and it is the philosopher of science Daniel Dennett who has given the best explanation of it by using set theory.
He starts off with a set of 'all the people in the world' and then one of 'their mothers'. These two sets will overlap a bit as some of the mothers are still alive. Then there are succeeding sets of 'their mothers' that don't overlap - as a mother cannot be a mother to herself. These sets become progressively smaller as they go back in time - as some women have no children and there are population of the world increases forwards in time, epidemics, wars, natural disasters etc.
Eventually you are left with a set containing one woman - Mitochondrial Eve. The problem arises when we ask the question - where did her mitochondria come from if not from her mother?