Another look at falsehoods about evolution.
We previously addressed the falsehood “Evolution has stopped for humans” and concluded that background change in allele frequency independent of natural selection does not just stop for any viable, continuing population. So, no, saying that “evolution has stopped for humans” is tantamount to saying that “gravity has stopped for my coffee cup” (which is sitting here on my desk minding its own business).
But this question is a falsehood at another level. In reality, there are two additional questions that are actually being asked when this question is brought up:
- Aren’t humans no longer subject to natural selection?; and
- Aren’t humans not likely to give rise to a new species?
The first assertion is a widely held belief with absolutely no foundation, so it qualifies as a true Falsehood. The second question is not so widely discussed. Here, we’ll focus on the first and leave the second for another time.
Are human beings “still” subject to natural selection? This is a loaded question: Loaded with tricky words like “are” and “still” and “selection” and “human being.”
Let’s start with the Are-Still problem. A species is an entity that has temporal (time) and spatial (geography) dimensions. So an expanding population/species covers more and more geography over time, and so on. The “Are-Still” part of this question must be referring to some part of that time-space continuum. I think what is usually meant by “humans” is humans in this modern world of medicine and dominance over the environment, etc. In particular, it means humans as a population not subject to scarcities of food, ravages of predation, and suffering by disease. This is because in many people’s minds evolution roughly equals natural selection and its effects, and natural selection roughly equals these listed aspects of the environment and their effects. The struggle for existence, the competition for food, and so on. And the struggle is over. (Remember, we’re talking Fallacies here … )
The other biggie, sexual selection, is often left out of the discussion. The popular mindset often seems to lack a concept of human mate competition or mate choice as factors in human evolution or human affairs in general. I think this is due to modern conceptions of monogamy. We fool ourselves into thinking that since there is the same number of men and women. and everybody eventually gets married to a member of the opposite sex, etc. , then there really is no mating competition or sexual selection. (Not true, not true, and not true.) This is a deeply fascinating set of assertions, beliefs, fallacies, and innuendos. Almost everything in evolution is about food and sex. But let’s deal with the food first, and save the sex for later. (Always a good plan.)
So “Are-Still” part of this fallacy addresses a particular temporal-spatial chunk of “Human Beings.” What about selection? Here the very simple (and meaningful but nowhere complete) answer is this: If we have removed with modern medicine, agriculture, and deadly weapons the parasites, predators, and food limitations from our environment, that does not mean that we are not evolving. What it means is that a large number of selective forces have shifted. Since we are talking mainly about stabilizing selection related to the ability to find food, avoid predators, etc. (maybe some directional selection as well), this mostly means that we are experiencing “relaxed selection.” This is when selective forces that were there are no longer there (relaxed).
Many people confuse this with “not evolving.” But remember our earlier discussion. “Evolution is change in allele frequency over time.” And remember that mutations are common, and that most of them are weeded out. So relaxing selection almost always has to result in increased rates of evolution. So not only are humans not “not” evolving, human evolution may be accelerated in some areas of the genome. What a time to be alive!
But there is, as you may already be thinking, another big problem with this. The “Are-Still” construct in combination with the environment being less “red in tooth and claw,” and all that, is problematic. And here we are going to get to the part of this discussion where many people will get mad at me. Sorry, but the assertion that we are not evolving because we have solved all of these problems is racist, classist, and Westernist. You are a bad person for thinking these things. But that’s OK, we still love you and you can change.
Different human populations are very closely related to each other, reflecting both recent separation of those populations and long term flow of genes across populations that believe falsely themselves to be separate. There are people right now living in some far off part of the world, whom you’ve never heard of (nor they of you) who are among the most genetically distant from you right now, among whom are individuals who’s great great great great grandson or granddaughter are going to have sex with your great great great granddaughter or grandson and thusly produce offspring. How do I know that? Because I traveled way back in time in an imaginary time machine I keep around for thought experiments, and made that prediction 100 years ago, 1000 years ago, 10,000 years ago, and 30,000 years ago and every time I was correct.
The modern human genome is fluid, it has been fluid for tens of thousands of years, and it will be fluid for whatever future exists until either the sun explodes or somebody really screws up and sends us into extinction.
Right now, as I’m sure you know, a huge part of the earth’s population of humans does not have protection by modern wonders of science from parasites. A lot of people in Uganda are eaten by lions each year. People often starve. In other words, the usual selective forces are very much at work in our species, somewhere, indeed, in many places. Many different forces of selection are at work to differing degrees in different parts of the world and at different times (leading to genetic diversification?) and gene flow is ongoing across the planet (leading to genetic variability that defies sub speciation?)
It was possible, maybe, 25 years ago or so, to incorrectly but convincingly hold up Western Culture and Civilization as the place/time where many of the environmental forces of selection have been reduced. However, more and more people each year living in Western Civilization are less protected because of increase poverty and a widening gap between the “haves” and the “have nots.” On top of that, some of the ravages of nature that we thought we were protecting ourselves from (like bacteria and viruses) are co-evolving with our defenses. And, presumably, or defenses are co-evolving as well. Yet another factor is the novelty of the environment. Some populations may have gotten out of being eaten by lions or running out of food, at least for the time being. But these populations have likely run into other problems. Obesity results in morbidity and mortality and may affect fertility or reproductive success in various ways. Obesity is growing to an epidemic in the US right now. Obesity as a consistent feature starting in childhood will certainly have selective effects. How can it not?
There are probably dozens of effects of “civilization” that have their own selective stories. So Natural Selection is still very much at work in the usual ways. Natural Selection in some areas is relaxed, thus changing evolutionary rates and trends, and not by any means eliminating them. And Natural Selection is working in relatively novel ways through the effects of changes in the environment caused by modernization.
So… Hypothesis: “Human beings are no longer subject to Natural Selection.”
More Falsehoods !!!
This post is one of a series on the topic of falsehoods. The following is a list of falsehoods posts in order:
- The Falsehoods
- “False Pearls before Real Swine”
- Falsehood: A baby is not the biological offspring of its adoptive mother
- Falsehoods: Has evolution stopped for humans?
- Natural Selection is Survival Of the Fittest (A Falsehood)
- Falsehood: Nature maintains balance.
- Is it a Falsehood that Humans Evolve from Apes?
- The poor and the dark skinned have more babies than the rich and the light skinned
- Acting for the survival of the species (a falsehood)
- Culture Overrides Biology (Another falsehood)
- What is the Placebo Effect, and it it getting stronger?