Question

The pattern of genetic similarity and differences among human populations allows us to reconstruct the evolutionary history of our species. Label the lettered parts of your answer.

A. What taxonomic group would include L1 + L2 + L3, but not Homo sapiens neaderthalensis?

B. Where and when did that (L1 + L2 + L3) taxonomic group originate?

C. Was there ever any interaction between (any part of the) taxonomic group you named above and Homo sapiens neaderthalensis; if so, what was the nature of that interaction?

D. Drawing on the information in your answers to parts A, B, and C, and on patterns of current human genetic diversity, explain the sequence and timing of events that led to the present situation, with a single kind of hominin occupying the whole planet.

Answer 1

Today, the oldest mtDNA haplogroups are found in Africa. The first haplo-groups were L1, L2 and L3, and they gave rise to other macro-haplogroups and branches of the global phylogenetic tree during the migration waves from Africa all over the world. Haplogroup L3 is ancestral to macro-haplo-groups M and N. They arose in northeast Africa and spread into Europe and Asia. Haplogroups H, I, J, N1b, T, U, V, W and X derived from haplogroup N, and at present they comprise the majority of mtDNAs in Europe. The Asian haplogroups A, B, C, D, F and G derived from M and N. Haplogroups A, B, C and D are frequent among Native Americans.

B. Before the migration out of Africa, three main lines of Homo sapiensdiverged from the !Kung line:bearers of mitochondrial haplogroup L1 (mtDNA)/A (Y-DNA), bearers of haplogroup L2 (mtDNA)/B (Y-DNA), and carriers of haplogroup L3 (mtDNA).

African hunter-gatherers that correspond to the mitochondrial haplogroup L1 are several groups of pygmies like the Aka and Efé from Congo, the Baka from Cameroon and the Hadza from Tanzania. Consistent with their genetic relatedness, they also share many cultural similarities. For example, their ritual gatherings revolve around storytelling, music, hunting and dancing, and there are no ritual fights involved. Also, little murder and violence is involved in their relationship with their neighbors and in all cases they rather have peaceful commercial relationships with neighboring pastoralist tribes such as the Bantu. Moreover, unlike the !Kung there is no archeological nor ethnographical evidence of war. It seems that in case of conflict all L1 mtDNA bearers choose to move apart rather than to fight.

African hunter-gatherers that correspond to the mitochondrial haplogroup L2 are the Mbuti from Congo. They also form a pacific society with no archeological or ethnographical evidence of war and where conflicts are ridiculed and jokes used to alleviate tensions. Again, their ritual gatherings involve music, storytelling and dancing, without ritual fights. And their wives value their men as long as they consider them good hunters.

Finally, descendants of the mitochondrial haplogroup L3 constitute the vast majority of hunter gatherers all over the world. The reason for this is that anatomically modern humans that evolved in Africa, migrated to Eurasia and Oceania within the last 80,000 years and then migrated to the Americas within the last 30,000 years. The geographic expansion of a small number of anatomically modern humans out of Africa resulted in a population bottleneck. For example, based on mtDNA studies it has been proposed that all non-Africans belong to one tiny African branch, bearers of haplotypes M and N, which are closely related in an L3 sub-branch, meaning that the entire human population outside of Africa is descended from only two closely related sub-branches of L3.