@The alchemist and
@Shimbiris are more knowledgeable on this field.
According to my understanding, C group and Kerma were almost identical and many believe they are just a continuation of one another. We have nothing to do with these Nile valley cultures but we are indeed of the same stock.
We descend from Gash which was like a parallel ‘sister’ culture to the aforementioned cultures above. Gash was further east towards the Red Sea Eritrea/East Sudan away from the Nile Valley. Gash is also the most likely location of Punt.