Wikipedia mentions "Since animal mtDNA evolves faster than nuclear genetic markers" with a few sources.
Some sources:
- Power, Sex, Suicide by Nick Lane (2006) page 361 mentions:so this property is also important for the human mitochondrial molecular clock.
While nuclear DNA can barely distinguish between chimps and humans, the mitochondrial clock ticks fast enough to reveal differences accumulating over tens of thousands of yearss
- www.ncbi.nlm.nih.gov/pmc/articles/PMC3350313 says it for metazoans
- www.quora.com/Why-does-mitochondrial-DNA-mutate-faster