This is major news: the authors of the study on the ancient East African genome of Mota have recanted their conclusions. In a correction note echoed by Nature they say:
The results presented in the Report “Ancient Ethiopian genome reveals extensive Eurasian admixture throughout the African continent“ were affected by a bioinformatics error. A script necessary to convert the input produced by samtools v0.1.19 to be compatible with PLINK was not run when merging the ancient genome, Mota, with the contemporary populations SNP panel, leading to homozygote positions to the human reference genome being dropped as missing data (the analysis of admixture with Neanderthals and Denisovans was not affected). When those positions were included, 255,922 SNP out of 256,540 from the contemporary reference panel could be called in Mota. The conclusion of a large migration into East Africa from Western Eurasia, and more precisely from a source genetically close to the early Neolithic farmers, is not affected. However, the geographic extent of the genetic impact of this migration was overestimated: the Western Eurasian backflow mostly affected East Africa and only a few SubUSaharan populations; the Yoruba and Mbuti do not show higher levels of Western Eurasian ancestry compared to Mota.
We thank Pontus Skoglund and David Reich for letting us know about this problem.
This makes much better sense admittedly. I strongly appreciate the willingness of Gallego, Jones et al. for publicly amending their wrong as quickly as possible. It's said that erring is human but correcting is only for the wise.