I believe it's just the opposite. The Mitochondrial DNA line is preserved in the females. So if an invader came in and killed all the males and took their women as wives exclusively, then the DNA record would show their descendents as having 100% DNA of the conquered people and no DNA from the invaders.
Fathers can be influential tooBiologists have warned for some years that paternal mitochondria do penetrate the human egg and survive for several hours... Erika Hagelberg from the University of Cambridge, UK, and colleagues... were carrying out a study of mitochondrial DNAs from hundreds of people from Papua-New Guinea and the Melanesian islands in order to study the history of human migration into this region of the western Pacific... People from all three mitochondrial groups live on Nguna. And, in all three groups, Hagelberg's group found the same mutation, a mutation previously seen only in an individual from northern Europe, and nowhere else in Melanesia, or for that matter anywhere else in the world... Adam Eyre-Walker, Noel Smith and John Maynard Smith from the University of Sussex, Brighton, UK confirm this view with a mathematical analysis of the occurrence of the so-called 'homoplasies' that appear in human mitochondrial DNA... reanalysis of a selection of European and African mitochondrial DNA sequences by the Sussex researchers suggests that recombination is a far more likely cause of the homoplasies, as they find no evidence that these sites are particularly variable over all lineages.
by Eleanor LawrenceIs Eve older than we thought?"Two studies prove that the estimation of both when and where humanity first arose could be seriously flawed... The ruler scientists have been using is based on genetic changes in mitochondria, simple bacteria that live inside us and control the energy requirements of our cells. Mitochondria are passed from mother to daughter and their genes mutate at a set rate which can be estimated - so many mutations per 1,000 years... However, these calculations are based upon a major assumption which, according to Prof John Maynard Smith, from Sussex University, is 'simply wrong'. The idea that underpins this dating technique is that mitochondria, like some kinds of bacteria, do not have sex... Two groups of researchers, Prof Maynard Smith and colleagues Adam Eyre-Walker and Noel Smith, also from Sussex, and Dr Erika Hagelberg and colleagues from the University of Otago, New Zealand, have found that mitochondria do indeed have sex - which means that genes from both males and females is mixed and the DNA in their offspring is very different... Prof Maynard Smith and his colleagues stumbled over mitochondria having sex in the process of tracking the spread of bacterial resistance to meningitis... For the 'out-of-Africa' theory to hold water, the first population would have to have been very small. Sexually rampant mitochondria may put paid to this idea. Maynard Smith thinks that the origin of humanity is much older - may be twice as old - which, according to Eyre-Walker, means we are likely to have evolved in many different areas of the world and did not descend from Eve in Africa."
by Sanjida O'Connell 15th April 1999