Over 6 million years our brain evolved from reptilian base level functioning (geared to keep us alive via fright and flight default setting) to what it is today- conceptual and emotional (& still evolving). Seems the reptilian brain is our default setting which is why we so readily revert back to our base level responses.
[en.wikipedia.org]
[humanorigins.si.edu]

This book is sooo interesting ... in my view worth every penny!

You miss the point with your tangent ... this topic and the book are about base primal instincts that give rise to tribalism/ racism.

@Earthling50 No, I don't think I do - I'm simply stating that although some things are natural, it's entirely possible for us as a species capable of abstract thought to bypass them. That's not a comment on your post or you, but on those who seek to use this sort of argument to try to excuse - or even advocate - racism.

@Jnei ...yes there are people who believe humans are superior to the rest of nature and therefore natural laws do not apply to them. The book debunks most of those myths. Still, its encouraging to see people making an effort to rise above their base level instincts respecting and getting along with others regardless of race or religion. That however is not the norm; its tolerance and civility that you don't find everywhere. A trip to Saudi Arabia or some other Muslim majority country will give you a reality check.