Mitochondrial DNA is that portion of inheritance that is primarily inherited from the female of a species. This property extends even into both plants and animals. The reason for this is that the only mitochondrial DNA introduced by the male is from sperm flagella and most of that is what is termed ‘trash’ DNA or is lost in the process. Mitochondrial DNA is mostly derived from the unfertilized egg. The ratio of Mitochondrial DNA in the female of a species has a prevalence of from 1000 to one to 100,000 to one over the male of a species.
If one considers that the oldest common bond between a common male and a common female in the human species is about 60.000 years (6000 years for creationists) ago and the average turnover time for a single generation is about 16 years over that time, no more than 4000 unions have occurred over the longer period. No more than about a tenth of a percent of male mitochondrial DNA can have survived the selection process if everything were equal (400 unions and .006% for creationists over the shorter period).
This is the reason that Mitochondrial DNA can be used as a marker for counting generations. The impurities introduced by the male mitochondrial DNA which actually survive in today’s homo sapiens act as a tracer of generations. The female mitochondrial DNA is the foundation.
The above thesis is highly simplified in its presentation and is only intended to convey how genetic lineage is calculated.
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