While it is good to have these experimental results, isn't it one of the primary characteristics of living things that they have an affinity for their own and that the closer the genetic relationship, the greater the affinity? The fact that racial difference may not have been encountered earlier in our evolution doesn't say anything about family/tribal differences that would account for differences in appearance that would be obvious to those in close contact and would readily substitute for and precede race. How many times have outsiders been at a loss to see physical differences that are clear to the "natives". Think of the Hutu and Tutsi, originally selected from the same pool of people. That even colored shirts, sports affinities and speech patterns can create visceral dislike that is entirely irrational indicates how readily we act in line with this nature of ours.
Japan would 'very clearly' prefer Britain remain in EU, says PM Abe (Reuters)
from the article: Are we born racist? A new Israeli study has some surprising answers