Human brains have definitely evolved to allow face recognition and distinction from infancy. There are people with "face blindness," prosopagnosia and they have difficulty distinguishing characteristics of their own face. I have heard someone with face blindness describe distinguishing between two faces similar to distinguishing between two similar river rocks.
It's a trained pattern recognition. When you see a face from your race, you already saw many others like it, so to distinguish people you trained to see the details. You see a face from another race you are not accustomed to, your pattern matcher says "hey, it's that _race_" and then it stops, as it doesn't know to distinguish details for that race.
An interesting study about this[1] shows that children exposed to other races (adopted and moved to another region) lose their initial training.
