This question can only be answered with two levels. In one sense, yes, what you write is true: different environments and different histories necessarily construct different organisms with different gene sequences that pertain to those different conditions which have determined their systems particular uniqueness.
In a certain sense, the whole issue has been improperly framed i.e. it has spawned from an intellectually glib postmodern culture which simply doesn't think in reasonable/coherent ways.
At a strictly biological level, there are differences that mostly arise from heat and light differences; so, African's have longer legs because animals at the equator need to dissipate heat, which is more effectively done when the core of the body is smaller, and the limbs longer. The reverse of this makeup can be found in Neanderthals and their barrelled chests, as well as Eskimo peoples who have evolved in the North. And light, or UV rays, determine the degree of melanin in the skin; melanin is a protein with the unique property of being able to breakdown uV rays, and hence, is again just a structurally evolved difference - but simply surface level.
At the neurological level, human brain-minds are enormously plastic, and so, constantly undergoing differentiation in terms of cultural elements and developmental history (i.e. critical periods which reify certain homeostatic patterns); and so, indeed, there is a quasi-behavioral difference between human ethnic groups, but at the same time, look at how malleable we are! Papua New Guinea aborigines can pick up and assimilate without problem any element of modern culture so long as they learn these skills early on. This strongly supports the image of a dynamically plastic process which responds more or less to the same relational meanings i.e. from the bottom-up, which is why its not a problem for aborigines to jump-forward thousands of years of civilization i.e. they already have the neurodynamical prerequisites to assimilate complex abstract knowledges about reality i.e. sciences, philosophy, etc
All in all, racism, or caring too much about race, reflects a small-mindedness that spends way too much energy focusing on minor and paltry differences, at the expense of very large and very general dynamics (i.e. recognition of needs) which more or less determine how well a society functions and how highly a person is able to regulate their emotions.
