By comparison, white humans have less than 1% of the genes of the less archaic Neanderthal, who additionally had a relatively developed brain, and whose evolution was geared toward survival under demanding conditions. The mixing of genes with humans may have occurred as little as 40,000 years ago, while hominids evolved separately for up to a million years. Quote from the study: We determined that the a posteriori average for the time of partitioning is 625,000 years before the present (B.P.) [95% highest a posteriori density (HPD) interval: 360,000 to 975,000], the time of admixture is 43,000 years B.P. (95% HPD: 6000 to 124,000), and the fraction of admixture is 0.11 (95% HPD: 0.045 to 0.19). Analyses of three other West African populations (ESN, GWD and MSL) yielded consistent estimates for these parameters (Figure 2 and Table S7). Combining our results for the West African populations, we estimate that the archaic population separated from the ancestor of Neanderthals and modern humans 360,000 years (ka) to 1.02 million years (Ma) B.P. and then introgressed into the ancestors of today's Africans from 0 to 124,000 B.P., representing 2 to 19% of their ancestry. We caution that the true underlying demographic model is likely more complex. We found that the median merger time of non-archaic segments is 0.865 Ma ago for both populations, while the median merger time of archaic segments is 1.51 Ma ago for the YRI and 1.15 Ma ago for the MSL (a 1.69- and 1.23-fold increase in age for the YRI and MSL, respectively).