I was thinking about evolution and natural selection one day, when a thought hit me : human evolution will not continue in normal society. Think about it - in the past, evolution worked because the animals with good genes survived long enough to have children, their only goal in life. If an animal had bad genes (too weak, too stupid, etc.) it would not survive to reproduce and the genes would not be passed on.
In modern society, this doesn’t happen. EVERYONE (barring those who die from unnatural causes, or disease, etc.) lives long enough to have children, because society protects them. If you’re mentally retarded, you won’t be killed by wild beasts because you can’t defend yourself adequately, or starve because you can’t hunt, etc. - society will protect you. If you’re weak, or have brittle bones or bad eyesight, etc. you won’t be killed in a fight over food, or territory, because the laws of society will protect you. And if you do get injured because you are retarded, or weak, or whatever, medical technology can most likely save you. Remember that Far Side cartoon? the plankton turns into a fish turns into a frog turns into a rat turns into a monkey turns into a strong, tall, caveman, who turns into a short, fat, bald guy with bad posture, waiting for the bus? Does anyone besides myself see this as a problem?
P.S. - I’m not making fun of fat people, or retarded people, or anyone else I’ve mentioned, so please don’t take offense.
P.S. - I’m not making fun of fat people, or retarded people, or anyone else I’ve mentioned, so please don’t take offense.
You may not be making fun of them, but you are placing a value on them. This is something evolution does not do.
Think about this: Early on in our history, we had to defend ourselves against predetors with only our hands. However, one smart fella figured out that using a sharpened stick made the job a bit easier. Would you say that evolution stoped working back then, as individuals who normally would have died at the hands of a hungry animal were subsequently able to fend off such attacks and live long enough to reproduce?
Society itself is a tool of sorts, and we all use it in one way or another to help us pass along our genes.
Your logic is quite similar to that of the eugenics movement. Remember, all that is required to be “fit” in evolutionary terms is the ability to reproduce. This says nothing about hair color, eye color, religious beliefs, mental capacity, etc.
Looks like Heembo sneaked in while I was typing, but I’ll start at the top.
Genetic evolution of humans will continue as long as every single person doesn’t have the same number of offspring, and as long as inherited characteristics affect how many offspring one has.
I think those conditions are going to continue to be met for quite some time (i.e. as long as I can imagine). I can think of lots of people who’ve died of inherited diseases without having any children. And for example, from what I hear, being able to play basketball really well can lead to many, many, many offspring (though I’m not sure how much of Wilt’s ability is genetic).
So evolution is definitely still happening. However, the selective forces have changed a bit over mankind’s history. For instance, in the U.S. today, very few people are being eaten by lions before they have a chance to raise children, so there’s not a lot of selection against slow running. On the other hand, a lot of men do die from heart disease, often before they fully raise children, so so being genetically resistant to heart disease is today a good gene that’s selected for.
And of course, selective forces could change in the future. Maybe spaceships will have limited size, so short people be are chosen for crews. If that makes them wealthier or have higher status, then being short becomes a good gene.
Is it a bad thing that lion predation isn’t a big selection force for humans right now? I guess the answer depends on what you think humans are here for, and what’s ‘good’.
Me, I’m kind of glad that being nearsighted or unable to run isn’t a fatal condition. I think the contributions of Ben Franklin, FDR, Thomas Edison, Homer, and all kinds of other people made the world a better place. I’m also glad that my parents haven’t been eaten by lions, even though they can’t run very fast any more.
Hi Quercus. I just wanted to clarify a few things you said.
Genetic evolution of humans will continue as long as every single person doesn’t have the same number of offspring, and as long as inherited characteristics affect how many offspring one has.
I’m not sure what difference it would make if everyone has the same number of offspring. Can you explain why you think evolution will stop when everyone has 1.5 children?
On the other hand, a lot of men do die from heart disease, often before they fully raise children, so so being genetically resistant to heart disease is today a good gene that’s selected for.
It really doesn’t matter what happens after you have the children, as long as THEY don’t die before they get a chance to have offspring. How many women ask a guy if their father died of heart disease and then decide not to sleep with them because of an answer in the affirmative? Remeber, all you have to do is get the girl pregnant…
And of course, selective forces could change in the future. Maybe spaceships will have limited size, so short people be are chosen for crews. If that makes them wealthier or have higher status, then being short becomes a good gene.
[Foghorn Leghorn voice]
No, no, no son, you’ve got it all wrong.
[/Foghorn Leghorn voice]
It don’t work that way. Socio economic status most likely shares a negative correlational value with evolutionary “fitness.” Look at average number of children per houshold, and you will find that as SES goes up, # of children goes down.
I know you were asking Quercus, but if nobody minds…
Fitness is a relative measure. If all members of a species have the same number of offspring, there can be no differences in fitness between the different genotypes, and therefore no evolution. The relationship between one’s genetics and the number of offspring, or evolutionary success, is severed.
I’m also not so sure about socio-economic status having a negative correlation with evolutionary fitness. A person has fewer children doesn’t necessarily have a lower fitness; more of their children may survive (r- vs. k-selected strategies).
I agree with your point about the heart disease. So long as your children survive to reproduce, it won’t have an effect on fitness. A similar discussion from IMHO took place a while ago.
Don’t confuse the PROCESS of evolution by the THEORY of natural selection. Evolution is basically change (usually towards some direction, although that path can change or double-back) which is always happening on some level and will continue, even within a given species in unchanging surroundings as they all have different sets of genes.
The means by which the next generation is selected from us all is generally accepted to be “natural selection” ; the fittest survive or end up out-numbering the inferior. Natural selection (the driving force OF evolution) doesn’t always favor the classic idea of fit, ie: biggest/strongest/fastest. Fitness is whatever gives you an advantage over your buddy in getting to the women (or men) and coming up with kids that survive to have kids of their own. Perhaps today the “fittest” are the smooth-talking scummy bar flies, or perhaps the low-income welfare moms with eigth kids and more on the way, or maybe even the men who make regular deposits to the sperm donors… whatever gets your seed out there. From a biological perspective, your kids don’t need to become rich or respected or happy, just as long as there’s lots of them and they pump out more copies of your family’s blueprint, you’re fitter than any olympic athelete or business tycoon. Natural selection will just favor whatever traits the times dictate, and those aren’t always gonna be the high caliber track stars.
Note from a previous poste; you don’t just need to get people pregnant - those kids have to survive delivory, childhood, and far enough into adulthood to produce children of their own in order for YOUR genes to be considered biologically fit. No use knocking up 50 women if your kids all die of some childhood genetic disease you passed onto them… your bloodline would be cut quite short.
Fitness is a relative measure. If all members of a species have the same number of offspring, there can be no differences in fitness between the different genotypes, and therefore no evolution. The relationship between one’s genetics and the number of offspring, or evolutionary success, is severed.
I had never thought of evolution from that angle before. Thanks for the insight.
I’m also not so sure about socio-economic status having a negative correlation with evolutionary fitness. A person has fewer children doesn’t necessarily have a lower fitness; more of their children may survive (r- vs. k-selected strategies).
I may have miscommunicated. What I was trying to say was that evolutionary “Fitness” should not be confused with economic prosperity. I attempted to illustrate this point by pointing out the negative correlation beween NUMBER OF OFFSPRING and SOCIO-ECONOMIC STATUS. In general, the more offspring an individual has, the more fit they can be considered in evolutionary terms.
Although I don’t have statistics to back me up on this issue, I would guess that a majority of the children born of lower socio-economic stautus parents survive long enough to produce offspring. I would also posit that the average number of children who survive long enough to bear children is higher in low socio-economic groups than it is in higher socio-economic groups.
[[Although I don’t have statistics to back me up on this issue, I would guess that a majority of the children born of lower socio-economic stautus parents survive long enough to produce offspring. I would also posit that the average number of children who survive long enough to bear children is higher in low socio-economic groups than it is in higher socio-economic groups.]]
Yeah, just ask Lee Kuan Yew of Singapore.
This is getting close to a Great Debates thread, but I hesitate as they’ve talked evolution to death… Not that David seems to mind.
Jill
Hi Heembo, I’ll clarify back (I was trying to be mercifully brief in my first posting), though it’s been covered well by others.
mmmiiikkkeee already made the point that when thinking about genetic evolution, ‘fitness’ isn’t about how many children of yours are born, it’s how many offspring you have at some distant point (i.e. great-great-great-grandchildren). Now, someone who has birthed lots of children will often have lots of great-etc-grandchildren, but not necessarily. Having quintuplets and then dying two weeks later so that they’re all starving orphans probably doesn’t contribute much to fitness. Nor does raising 18 children and sending them all to celibate monastaries.
So even after they’re born, as long as you’re still helping out your children in some way, staying alive is a good thing, evolutionarily speaking. And thereofore having a fatal heart attack is a bad thing.
On to social status: being of higher social-economic status is a good thing in and of itself, evolutionarily speaking (and all else being equal). Wealthier people are on average healthier and less likely to die prematurely than less-wealthy people (Quercus pleads lack of time to find the cite). So a magic gene that makes your offspring rich is a definite plus to fitness.
However, I also want to stress that being rich and powerful today has just about nothing to do with genetics and everything to do with environment – growing up in a wealthy household, having the means to go to good schools, benefiting from your father’s connections… it has to do with family, but nothing to do with genetics.
And it is also possible to change socio-economic status from generation to generation. Plus, keep in mind that genetic evolution happens on scales much longer than a couple of generations – in other words a longer time period than our current social structure has lasted, so it can’t of had much of an effect on genetic evolution.
In other words, evolutionary theory is fairly straightforward, but the real world and how humans live and interact is very, very complex.
So genetic evolution and socio-economic status have at best a very subtle and complex relationship. In the real world, broad statements connecting them in a simple way are almost certainly wrong.
[sorry if this last bit got a little long; I thought it was important to add that given this century’s history of mis-using evolution to justify things]
Re the fatal heart attack: truly, it would be a bad thing, but if your children still reproduce, its effects on your evolutionary fitness are negligible. Beyond parental care to ensure the survival of young to reproductive age, there’s little fitness advantage in living past your own reproductive age (although Jared Diamond has pointed out that there is some advantage in social organisms). Having the fatal heart attack after the young 'uns have established their own families would be bad, but would not have a terrible effect on fitness. Genetic diseases that manifest in old age are not likely to have been selected against.
Re socio-economic status: I think Quercus is right on the ball here; socio-economic status is a result of environmental factors and is unlikely to have a large impact on fitness of a genetic lineage over a long period of time.
Wealthier families do tend to have fewer children, but I suspect this is a fairly recent (and I would hope, transient) trend. Limited to the past couple hundred years in the developed world, and is it even discernable over most of the world? I’m not sure because I don’t know much about the demographics of childbearing.
I agree with you on these suspicions, but I would qualify that with “in the developed world.” Most of the planet’s humans may live under different conditions. YMMV.
My thoughts about the eventual evolutionary impact of this: it’s not going to amount to much. I don’t think there will be a link between genotype and socio-economic status for long periods of time into the future (I suppose it’s arguable whether there is one now). Then this effect will amount to some random (with respect to the genotype) drift. That assumes the effect will be sustained for a long period of time. I’m not sure how long wealthy folks have had reduced numbers of offspring, but I’ll bet it’s started pretty recently in human history and isn’t worldwide, either. The limited extent of this effect in time and space makes me doubt it will leave a lasting impact on human evolution, although it makes for interesting speculation.
