Final answer:
The MRCA of human mtDNA lineages lived in Africa between 100,000-200,000 years ago, as indicated by phylogenetic analyses of mitochondrial DNA. This DNA is passed down exclusively through the maternal line, allowing researchers to study the origins of modern humans.
Step-by-step explanation:
The MRCA (Most Recent Common Ancestor) of human mtDNA lineages is estimated to have lived in Africa between 100,000-200,000 years ago, as indicated by phylogenetic analyses. Mitochondrial DNA (mtDNA) is used to study the origins of modern humans because it is passed down exclusively through the maternal line. By analyzing mutations in mtDNA, researchers have traced the ancestry of all modern humans back to a common female ancestor who lived in Africa around 200,000 years ago.