Jgnat the Genographic project uses mitochobdrial DNA which is passed only through the egg. Thus, it is not a combination of male and female genes. It is a haploid gene - meaning that it has only one dose of chromosomes. The haploid mitochondrial DNA shows only the female lineage of a person. Diploid genes are two sets of combined chromosomes, the female set coming from the egg, the male chromosomes from the sperm.
Mitochondrial DNA is categorized into several types and groups termed haplotypes and haplogroups. That is, there are variations in the genetic code of mitochondria that fit into clusters. These clusters can trace lineage far back into time.There are 39 different and distinct mitochondrial DNA groups into which all humans fit and there are variations on these types.
While mito chondrial DNA analysis is not only easier than other forms of genetic testing, it has a further advantage. All DNA mutates over time. But mitichodrial DNA has a fairly steady rate of mutation that permits a reasonably accurate estimate of exactly when a particular group of people migrated from their primary group.
Thus, two important factors can be determined through analysis of mitochondrial DNA. First, a living person (or the mitochondrial DNA from the remains of a deceased person) can be tested to determine the specific racial group from which the Individual came.Secondly, the approximate time when that Individual's ancestors migrated from their primary racial group can be determined.
One way to view mitochondrial DNA testing is that it may be able to provide a racial family tree extending back to the beginning of humanity. The current idea in mitochondrial DNA analysis is that ancestry on the female side can eventually be traced back to a common ancestor (sometimes referred to the "Genetic Eve"). The 39 types of mitochondrial DNA were presumably derived from this ancestor.So you can imagine the implications of that!