Source: Nathaniel T. Jeanson, "On the Origin of Human Mitochondrial DNA Differences, New Generation Time Data Both Suggest a Unified Young-Earth Creation Model and Challenge the Evolutionary Out-of-Africa Model," Answers Research Journal, September 2016.
"Previously, I predicted that a constant rate of mutation over 6000 years would result in 20 to 79 mitochondrial genome-wide nucleotide differences. This prediction captured the average non-African mtDNA difference (38–40 nucleotides) quite well. However, after the paper was published, I was made aware that the upper end of this prediction (79 nucleotides) also barely captured the average African DNA difference (~77 nucleotides; average from Ingman et al. 2000). To reach this difference of 79 nucleotides, a constant rate of mutation and a generation time of 15 years had to be assumed. Since a 15 year generation time is at odds with typical practices today in the West ..."
"In African nations surveyed around 1976, nearly a third (32.8%) of women were married by ages 15-19 ... This percentage was nearly three times higher than the percentage among women from non-African nations. ... Since mtDNA in humans is thought to be inherited primarily through the maternal lineage, this finding cast my previous mtDNA calculations in a new light."
The author goes on to explain that if the evolutionary model is accepted, then there is a severe shortage of mtDNA differences to reach the timeline evolution requires.