Correct me if I'm wrong. The Mesolithic dating of Elmenteitan A was done on the assumption that all the bones found at Bromhead's site cemetery were contemporary.
"The UCLA radiocarbon sample was processed under the assumption that a mixture of skeletal parts of different individuals who are contemporary should yield a date of that time period."
Elmenteitan A skull wasn't a part of the fragments that were dated. The radiocarbon dating was done on a mixed group of fragments that didn't include the skull.
"epiphyses of fibulae and ossa calcis of several juveniles, tali of at least three individuals, several lumbar vertebrae, parts of two left femora, parts of three tibiae, and fragmentary pieces of humeri".
"Future absolute dating should concentrate on a comparison of individual dates of different skeletons"
Stratification at the site was poor and samples were mixed together with the changing water levels. Isn't it possible they conflated the Mesolithic HGs with the Eurasian pastoralists?