https://drum.lib.umd.edu/handle/1903/11443
Page 122:
"Besides the Boni and Sengwer, all current East African hunter-gatherers share common haplotypes (mtDNA L4, L3a, L0d3 and Y chromosome B2a and B2b), suggesting that the current East African hunter-gatherers might represent remnants of the previous pre-Holocene and early Holocene population in the region. The Boni and the Sengwer appear to have had substantial levels of gene flow from other neighboring populations that appear to have the hunter-gatherer “genetic signature”. In fact, the Orma and Kalenjin populations that neighbor the Boni and the Sengwer, respectively, carry hunter-gatherer haplotypes at moderate frequencies indicating possible “reverse” gene flow."