Just curious we’re genetically closest to them but before they expanded they were native to the north western part of Kenya so how did we come to be genetically closest to them? Wouldn’t we be more closer to the afar or habash or even Amhara than them? Did we intermix with them a lot and did it change our phenotype. It probably reduced the amount of Eurasian we had which is my guess but I’m not knowledgable on the topic and curious to find out more
It's complicated and I too fully don't understand. But I can answer some of your questions.
Our Eurasian to sub saharan african was probably the same at 40:60 and was never affected since back migration. We remind homogeneous for centuries. So we never had the added Eurasian of 10 to 15 percent found in Ethio semetic groups as well as northern Cushitic groups such as Afar, Beja, Saho and etc. These groups have the extra Arabian in their DNA (most likely from yeman) which is between 20 to 35 percent depending on the ethinic groups. Beni Ameer and Beja can have up to 35% Arabian, Eritreans habesha and Afars 30%, Ethiopians Habasha 25%, northern oromos living close to semetic habasha can have between 15 to 20% and we somalis have on average 5%. This is probably similar to Borana and southern oromos who like us were not affected by the recent Arabian migration.
If I estimate the timeframe of this Arabian migration, I would say between 8th to 16th century. This was when the semetic habasha had the lands of south yeman in their control.