Ancient West African foragers in the context of African population history

Ancient West African foragers in the context of African population history

Lipson, M., Ribot, I., Mallick, S. et al.

This paper focuses on analyzing genomic data from four juvenile individuals from the archaeological site of Shum Laka, Cameroon. Comparing the DNA from these individuals to the genomic profile of modern day individuals from Africa, with emphasis placed on western Central Africa, hunter-gatherers, and farmers. They retrieve DNA samples from four out of the six petrous bone samples. Two individuals date to the early Stone to Metal age (8,000 bp) and two individuals date to the late Stone to Metal Age (3,000 bp). They used Illumina sequencing, as well whole-genome shotgun sequencing for two individuals (2/SE II and 4/A) and sixty-three individuals from five present-day Cameroonian populations.

The two earlier individuals carry the mtDNA haplogroup (L0a2a1), a widespread haplogroup in Africa. The two later individuals carry L1c (L1c2a1b), common in farmers and hunter-gatherers in Central and West Africa. The rare Y chromosome group A00 was found in individual 2/SE II (8,000 bp), which is found only in the western part of Cameroon. A00 is the oldest known branch of Y chromosome tree, splitting roughly 300,000-200,000 bp. They then used a PCA analysis to compare the relationships between the four individuals and present day and ancient sub-Saharan Africans.

The samples show admixture with about 35% ancestry from related hunter-gatherers from western Central Africa and about 65% from a basal West African source. The study also reveals a ghost source that contributed to West Africans and East African hunter-gatherers, which is consistent with other reports of archaic ancestry in African populations.

Overall, there were a series of population splits involving West African related lineages and two East African related lineages, as well as non-Africans. This suggests that the center of the radiation was possibly in East Africa, with estimated divergences of African and non-African populations placed at 80,000-60,000 bp. The results also showed that the Central African hunter-gatherers split 250,00-200,00 bp or earlier and they would later diversify. This paper shows there were at least four modern human lineages that diversified 250,000-200,000 bp.

Kailie Batsche
Potluck article for 4 February 2020

Article: https://doi-org.proxygw.wrlc.org/10.1038/s41586-020-1929-1
Photo: MATTIAS KLUM/NATIONAL GEOGRAPHIC IMAGE COLLECTION/ALAMY STOCK PHOTO