Modern Evolution

Are people continuing to evolve, physically? Assume that we have changed dramatically in appearance since olden times (we have gotten taller). But have we changed in other ways?

Evolution never stops, but I think it’s safe to say that we are influencing our own evolution in unprecedented and unknown ways. As for getting taller, that’s more a result of better medicine and nutrition than of evolution.

What’s the difference? It’s more like we’ve helped accelerate evolution – or guided it. The better medicine and nutrition has allowed the human body to adapt differently.

Adapting to one’s environment = Evolution (sort of, you get the picture).

As for the OP. Um … I don’t know. Maybe. Are we less hairy than we were 1000 years ago? Are we darker as a whole? Lighter? Bigger lung capacity? Less? How could we tell? I doubt it would be very easy to gather that sort of data on an adequate number of people from thousands of years ago. And since evolution is only really noticable over longer periods of time than that, we may never know.

What will probably happen is that 5000 years from now, people will compare us with people from 5000 years ago and be able to indicate the differences with an entirely new frame of reference.

I think what I’m trying to say is that you can’t really “see” evolution when your smack dab in the middle of it.

Which upon re-reading is pretty much what you said.

[Emily Latella]
[/Emily Latella]

My favorite example is how our jaws are shrinking and our third molars (wisdom teeth) are being crowded out or simply not existing in at all. They served a function at one time (chewing things that would make granola seem like pudding) and having a nice big jaw with lots of big molars gave an advantage in the survival game. As time went by we started to pre-grind our food and wisdom teeth became less of an advantage.

Without the need to chew wood such a large, heavy, calcium-rich jaw with big, hungry muscles to power it became almost a liability, or, at least, presented no advantage. Mutations that resulted in smaller jaws and no wisdom teeth were not liabilities and the people carrying the mutation could breed. However, when you got a small jaw AND wisdom teeth you ran a risk of a fatal abcess. Modern dentistry removes the extra teeth, modern medicine kills the infection, and we survive to pass along our faulty genes. So much for the continuing evolution of humans.

But if you made our nutrition worse and removed our medicine, we’d be pretty much the same as we were before.

Nutrition and medicine don’t by themselves affect the gene pool directly. Clearly though, there are people who lived to reproduce who would not have made it without medicine or better nutrition, but IMO that’s not a direct effect.

There really hasn’t been enough time for nutrition and medicine to have that big an effect on our gene pools. But since I’m not very well studied in this area, I will now brace myself to be corrected by those far more knowledgable.

The reason it isn’t evolution is that evolution requires genetic change, not somatic change. What is evolution? It is the differential reproduction of alleles between generations. If you take two herds of sheep and feed one grain and the other one thistles, the grain-fed sheep are going to be bigger and healthier. The thistle-fed sheep are going to be puny and stunted. But there is no evolutionary change in either population, if you take the puny population and feed them grain they will get larger and vice-versa.

So what we have to look at are whether there are some alleles that are more likely to be overrepresented in future generations. If people with blue eyes have more children than people with brown eyes, that is evolution because eye color is under genetic control.

I think we have seen some evolution over the past few thousand years. I suspect that the ability of adults to digest lactose has been selected for among dairying cultures. I also wouldn’t be surprised if different populations had varying responses to alcohol, based on how long alcohol has been available in those populations.

Molars not coming in at all? I don’t think evolution works that way.

If not growing molars is an inherited genetic trait, and if that trait provides a survival advantage, then people without molars would, over a very long period of time, become more numerous than folks with molars.

But now that we can safely remove molars, the survival advantage is gone. So, in this example, natural selection is subverted by science.

On the other hand, geneticists might isolate the gene for growing up molar-free, splice it into embryoes and eliminate molars in one generation. That’s genetic engineering - not evolution. At least, not evolution through natural selection.

If you want to expand the definition of evolution to include intelligently modifying our genome, then OK. Is that the question that the OP is really asking?

[wild speculation]Personally, I think that within the next 200 or 300 years, genetic engineering will render natural selection for humans obsolete. And a few centuries after that I expect that we’ll manage the entire earth’s ecosystem like one huge farm. Then a supervirus will wipe us all out. [/wild speculation]

Cecil’s Take

Lemur explained what I was getting at with nutrition and height in humans.

women prefer taller men which apart from nutrition is why men are getting taller.

evolution only stops if the environment stops changing and it never does… also do not disregard the effect of sexual selection - part of natural selection - the peacock has a big flashy tail because the girls like it.

i advise you read the mating mind by geoffrey miller and dawkins selfish gene - or even better almost like a whale by some guy i cant remember… its a lot more complex than you think

This would only be valid if you could show that women are not only “preferring” taller men, but that women were actively rejecting shorter men–(I don’t know any short guys who were not able to get married and have kids)–and that the women who chose taller men chose to have more children than those women who “resigned” themselves to mating with shorter men.

Taller men may have some sort of “earlier” selection of mates, but since even among polygynous societies we do not generally have a “herd sire,” I doubt that we are actually breeding for height.

Ah, but tomndebb, you forget the modern lesson of the Chickadee! Just because two people get married and have kids, doesn’t mean the wife wasn’t sneaking nookie from the studmuffin down the street while her husband wasn’t looking.

So only the tall guys are getting any extracurricular activity?

It wouldn’t necessarily have to be the case that tall guys are the only ones getting any extracurricular activity. Only that guys (and girls) with “tall” genes are reproducing more frequently than guys and girls with “short” genes.

The big thing to remember is that selective advantages are usually NOT survival advantages. Much more important are reproductive advantages. Sure, you can’t have any kids if you’re dead. But many genetic traits don’t kill you but definately impair your fertility…either through impaired ability to mate, or through impaired ability to produce gametes, or carry a baby to term.

If we look at modern society, we see that many people have no kids, for many different reasons. Other people have many kids, again for many different reasons. It seems to me that most of these reasons are non-genetic, but there are still many that are genetic. As long as people with different genes reproduce at different rates, we have evolution by definition.