One of the most famous examples of accelerated natural selection is that of the peppered moth. The moths changed color to better blend in with soot-covered structures and trees.
Is there any example of something similar happening as a result of extended periods of war or violence in a region?
Not to my knowledge. For natural selection to be effective in changing gene frequencies, it has to be maintained over a period of many generations. (Or else it has to be extremely severe, well above the fatality rate in any major conflict.)
I’m not necessarily looking for the natural selection being the direct result of violence-driven deaths of a population. It might be because war substantially changed the environment of a region.
For context, I’m collaborating with a science teacher to create a series of lessons at the intersection of science and war. So I’m looking to hit natural selection from that angle if there’s a way to do so.
The way you stated this kind of implies the moths had (conscious) choice to do this. It is better stated (and in line with how evolution/selection works) to say “the moths that happened to change color to blend in with the soot-covered structures and trees, survived (to propagate)”
The 14th century was a terrible time, plagued by wars and well, plague. The Black Death alone is thought to have killed up to a third of the world’s population. Should that have accelerated natural section to produce hardier humans, since both war and disease tend to disproportionately affect weaker people?
Research focusing on post-plague-era differences suggest there may have been some evolutionary advantages to surviving it, but it’s far from conclusive.
Natural selection favoring reproductive viability and success in wartime conditions? What would that look like?
It’s a science fiction trope, to be sure, but it’s depicted as unnatural selection, as in manipulating the behavior of a sentient race to engage in wars they can’t win in an effort to reduce aggressive tendencies (by killing off the most aggressive and warmongering individuals). See Larry Niven’s treatment of the Kzinti race.
I think I may not be communicating this very well. As a hypothetical:
Perhaps war in a region resulted (for whatever reason) in mass deforestation, decimating the food supply of a particular type of bird. This created evolutionary pressures which favored birds who were able to successfully feed on alternate food sources. Something simple like that.
The main effect of the Black Death in the UK was to open up opportunities for survivors to become upwardly mobile. People who waked the land in serf-like conditions were suddenly able to acquire property and become farmers in their own right.
There is historical evidence of people at the bottom of society opening up shops etc, but this was unrelated to genetics, jut the chance of avoiding premature death.
The question would be whether there was some kind of heritable trait that conferred an advantage for survival under those circumstances. Like say… some sort of biochemical quirk that made one less prone to getting the Black Death, or maybe lets you have a higher chance of surviving it.
The only things I can think of warfare wise in that era might be something like faster reflexes, more endurance, or the most likely, resistance to disease/infection. Over generations of soldiering, I’d think that it’s possible that genes to enhance resistance to disease and infection could become selected for in certain populations.
I’m having trouble thinking of instances in war (specifically) caused long-term environmental changes over large areas.
When European and African diseases largely decimated Native American populations in the Americas after Columbus’s voyage, agricultural areas in many places soon reverted to forest. But that was more the result of disease rather than war, and I am not away of distinct selection pressures created by forests.
Human genomes may show the long term selective results of disease, and perhaps change in diet (e.g. the spread of genes permitting the digestion of lactose by adults in Europe). But it would be hard to pinpoint the effect of wars.
It’s theoretically possible for massive mortality in war to change gene frequencies in the next generation. However, once the war is over the selection pressures will generally revert to what they were before the war, and so any changes won’t be propagated.
Well, you’re going to have o come up with a more common and longer lasting side effect of war than deforestation, istm. I’m sure school kids might not notice but I would definitely feel like you were trying to shoehorn natural selection into such a learning program if you used “deforestation from a war” as an example when it’s not really common and there’s hundreds of better studies of deforestation in non-war contexts.
I think a lot of folks are assuming that the OP is talking about changes in humans, but he never actually says that, and in fact his two examples are birds and moths.
How much area was hit by Agent Orange, in Vietnam? That’s the best example I can think of for war-caused environmental change.
It’s a hypothetical. I’m not trying to shoehorn anything. I’m wondering if there are any documented real-world examples of war causing a significant enough environmental impact to accelerate natural selection.
That seems promising - I know there’s been a ton of research on the long-term environmental impacts of Agent Orange.
Another one that may be worth looking into is the Western Front in WWI. Besides the chemical warfare, some of the areas were once forests before being shelled into a cratered wasteland. Maybe the trenches themselves also physically cut off and isolated wildlife populations as well?
I know it’s a hypothetical. “Natural selection” just seems an odd choice for a “war and science” subject.
To stick with the hypothetical, the most famous American war relatable deforestation is the use of Agent Orange in Vietnam. I have no trouble believing that had an effect on natural selection either immediate or long term. It would feel shoehorned into a “war and science” subject because there’s plenty of better examples of the effects of deforestation and herbicide use than the Vietnam War. So my point was that if you really want natural selection in there, it would be better to find something more common and specific to wars. Like populated areas being emptied, increases in manufacturing, leftover war materials all over the place or something. I’m really just suggesting a line of search.
double post
I might have a bit of an example of war impacting natural selection of some non-human species, but I don’t think it’s quite correct to call it “accelerating” natural selection.
A work colleague had the opportunity to spend several months in Croatia after their war in the early 90’s, and his job was to help establish a fish culture program to restock the water bodies. It seems that the war had caused a lot of poverty and the locals took to fishing everything they could to survive. The war basically forced massive over fishing in the area which decimated the fish stocks. I don’t have the details of what species or to what extent, but it was bad enough that their government asked other countries for help.
Over-harvest of a population can have very large genetic impacts by reducing genetic variability. The Wikipedia page on genetic bottleneck describes this a bit, and in the first line even refers to one possible cause as human genocide:
There are probably lots of examples of less resilient shorter-lived species having their habitat destroyed or their numbers vastly reduced as a result of human warfare, which would lead to genetic consequences.
Have there been any observable effects in the Zone Rouge in France? There are areas where only few types of plants grow, because of the high concentration of heavy metals in the soil. But are there any observable changes in plants or animals over the past century?
I would argue, without my tongue in my cheek, that war has in fact been maintained over a period of many generations. There’s no way that war hasn’t affected natural selection in humans, to an absolutely massive degree. But it’s not something that’s easy to measure or study.
The question, I suppose, is whether such selection would lead to greater reproduction among surviving soldiers (most sent to war shortly after reaching sexual maturity) or people who did not go to war. My speculation would be that the evolutionary favor would go to the peaceful. Since, you know, soldiers die.