At some future period, not very distant as measured by centuries, the civilized races of man will almost certainly exterminate and replace throughout the world the savage races. At the same time the anthropomorphous apes, as Prof. Schaaffhause has remarked, will no doubt be exterminated. The break will then be rendered wider, for it will intervene between man in a more civilized state, as we may hope, than the Caucasian and some ape as low as a baboon, instead of as at present between the negro or Australian and the gorilla.

We can see this point by making an analogy between populations and families. Blue eyes are inherited in a roughly recessive fashion. That means that two brown-eyed parents may have two children with blue eyes (as in the chart to the left), while two people who are unrelated may share the same blue eyes. Clearly on that particular gene, two unrelated individuals can be more similar than parents and their own offspring. But it doesn’t follow from this that parents and offspring are less genetically similar overall than strangers with the same eye color. Rather, it tells us to be careful of extrapolating from just one gene when it comes to thinking about overall patterns of genetic relatedness.
This is false. 5 to 10 thousand years ago a set of strangely mutated humans arose. They continued to be able to digest lactose sugar as adults, in contravention of the mammalian norm. In fact, humans are the only mammals where many adults continue to be able to consume milk sugar as adults. The rapidity of this shift has been incredible. 5,000 years ago almost everyone in Scandinavia was lactose intolerant. Today, very few are. The area of the European genome responsible for this shift is strikingly homogeneous, as a giant DNA fragment “swept” through populations in a few dozen generations.

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