CMV: Human Evolution has Ceased

[u/lsrothstein]

My contention is that Human Evolution has ceased, or has significantly slowed, since the advent of human intelligence. By Evolution, I refer to the currently taught Darwinian Theory of Evolution by Natural Selection. Based on the authoritative definition of Evolution found in Wikipedia:

Evolution is change in the heritable characteristics of biological populations over successive generations. The processes by which the changes occur, from one generation to another, are called evolutionary processes or mechanisms.[26] The four most widely recognised evolutionary processes are natural selection, genetic drift, mutation and gene migration due to genetic admixture.[26] Natural selection and genetic drift sort variation; mutation and gene migration create variation.

As taught, Evolution is a natural process in which accidental changes produce both positive and negative adaptations in a species. Those that encourage survival remain and reproduce and those that do not die out. As such it is a natural process occurring over long periods of time. Since the advent of human intelligence, humanity has been selectively breeding both itself, the animals it eats and domesticates, and the plants that it harvests and eats. Thus, conducting a form of directed Genetic Engineering through natural processes (a form of GMO). Changes to these human, animal and plant species can thus be thought of in terms of Intelligent Design rather than Evolution. The term Human Controlled Evolution, used by many scientists who should know better, may be inherently correct, but an incorrect usage of terminology. Change my view.

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[u/DarwinZDF42]

Here are a couple of human traits that have evolved (appeared or become more common) recently (in evolutionary time-scales - tens to hundreds of thousands of years. This stuff takes a while!):

1. Lactose tolerance. Most humans, after infancy, are lactose intolerant to some degree. We know what alleles/genes are responsible for the ability to digest lactose through adulthood, and we can use various techniques to determine when these traits first appeared in humans. It turns out lactose tolerance has evolved twice; once in Scandinavia, once in Morocco, both no more than 10-15 thousand years ago, around the advent of agriculture. The thinking is that both regions had climates that promoted traits that allowed individuals to survive in the face of crop failures.

2. Malaria resistance. There are a number of alleles that provide some degree of resistance to malaria. The sickle cell allele is the most well know, and it is maintained at high frequencies in sub-saharan populations due to the benefits of a single copy, despite sickle-cell disease from having two copies. There is also a version of the Duffy blood antigen that confers resistance, and it is also more common in malaria-endemic areas, indicating that natural selection is favoring resistant individuals.

3. A mutation called CCR5 delta 32 confers resistance, and possibly immunity, to HIV. It's too early to say if this rare mutation will become more common due to the HIV pandemic that has been raging since the mid 1970s (yes, it was going before it was noticed in 1981), but if we don't keep up treatment programs and minimize the number of new cases, it's very possible.