It is quite common to name the growing human offspring as embryo or fetus regardless of the period of intrauterine life. Over many generations, the number of individuals bearing the adaptive characteristics increase until all individuals have them. Genetic fitness is the overall ability to leave surviving offspring who themselves will be able to reproduce successfully. Mitochondrial Eve theory does not say that at some point in the history there was one female member of our species. The difference between gene and individual genealogies is important in the interpretation of the findings led to this theory.
All genes eventually coalesce into a single common ancestor.
The mitochondrial Eve was not necessarily the only female alive at that time, nor the first female to have that particular type. Many other mtDNA lineages may have gone extinct before her. Linkage, association and linkage disequilibrium are all different concepts. The HLA-A locus and hereditary hemochromatosis show linkage in families. Anti-oncogenes are not genes that antagonise the effects of the oncogenes.