What's triggering the chimpouts?
The technical answer is “archaic hominin genetic introgression in west african populations. “
Yep.
https://reich.hms.harvard.edu/sites/reich.hms.harvard.edu/files/inline-files/Shum_Laka_published.pdf
Figure 4 (on page 4) is illuminating.
Look at the graphic from this study which analyzed varients of the MUC7 salivary protein. It suggests hybridization in yorubans with a species that diverge ~4.5 mya. That is close to the split with Pan. (Group E)
https://files.catbox.moe/vhnicu.jpeg
Archaic Hominin Introgression in Africa Contributes to Functional Salivary MUC7 Genetic Variation https://academic.oup.com/mbe/article/34/10/2704/3988100
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