Evolution and Modern Medicine.

What effect is modern medicine having on human evolution? Good or bad?

It would seem to me (although I could be wrong), that more defective people are just passing on more of their defective dna.

As to what is the solution if this is true (which as I explained, is still a big If), I don’t know. Eugenics is such a nasty and outdated word. But there is always genetic counseling, for couples with certain genetically-passed on disorders.

What do the rest of you think about this subject?

:):):slight_smile:

If they’re successfully reproducing, is their DNA defective?

The difference between eugenics and genetic counseling is the difference between me saying “Zere vill be no babies wiz Huntington’s disease!” and someone who’s a carrier for it deciding on their own to adopt rather than try to have a biological child.

If medical science can correct these defects, or make them survivable, then by definition, in the context of evolution, that DNA is no longer defective.

I often see people claiming that evolution no longer works on humans, or that we’ve escaped natural selection. What’s really happening is that we are changing our own environment, and therefore, altering the selective pressure acting on our species. I do agree that as a whole, our species is currently experiencing much less selection than do most species, or than we did in the past. But without a time machine that lets us look into the future, we can’t call that “good” or “bad”. I suspect that, barring a total collapse of civilization, medical science will help us fix problems faster than evolution can act.

Medicine allows more people to survive and contribute to society. That’s good. Assuming we are hurting ourselves by letting “defective” people survive because we won’t meet an arbitrary standard of genetic purity is very eugenics-ish, yes.

Which of these “defective” (how are you defining this, by the way?) would have grown old enough to have children before the advent of modern medicine? Probably nearly all of them.

Well, all of them were still passing their genes happily along before. It doesn’t much change the genetic situation if they are still passing their genes along happily to their children but now have the added benefit of modern medicine to help them live longer, more fulfilling lives.

Also, just because the people you deem “defective” might have a few more kids now than before doesn’t stop “non-defective” people from breeding. The human gene pool isn’t going to be weakened from having a slightly greater variety in it, especially when we have so many samples of what just about everybody will agree are “normal” people. The concept that a few non-desirables could even possibly do harm to human evolution absolutely is eugenics wrapped up more politely. It doesn’t make any real biologic sense.

Who of us does not have some (lots of) defective DNA? Who would decide that the DNA is so defective that the carrier should not be allowed to reproduce? It usually turns out defective means “not like those of us with power.”

I for one like that there are a lot of defective DNA out there. Less competition for me

I was first confused that someone with a 2002 join date wouldn’t have seen this topic debated here a dozen times since then, but your post count is pretty low, so you’re probably out more than in.

True, but so what? They’re not eliminating any of the “good” genes, and who knows what is going to be a good or bad gene 500 years from now?

Taking cystic fibrosis for an example. It is a recessive, single gene trait, inherited on chromosome #7.

As of about 25 years ago there was significant childhood mortality. Patients simply did not live long enough to reproduce. As each patient died tow “defective” copies of the relevant gene were removed from the gene pool.

With identification of the gene and better treatment the life expectancy has gone up substantially. Patients typically live into their reproductive years. However the disease process affects fertility.

A large majority (around 98%) of men with CF are infertile without using assisted reproductive techniques. This is due to part of the disease process that causes a failure of the vas deferens to form normally. Women with CF have more or less normal fertility.

So now more people with CF live to pass on their genes. Some will use assisted reproduction with pre-implantation genetic testing. This can actually lead to an increase in “defective” gene frequency making the gene pool, as a whole, sicker. All courtesy of modern medicine.

Human evolution is so slow thanks to our long generation times that there just hasn’t been enough time for modern medicine to have a significant effect.

And as for the future, either society will collapse and modern medicine won’t exist, or society will advance and our descendents will simply fix any inconvenient defective genes. Modern medicine isn’t going to have long term effects because it isn’t a long term phenomenon, it’s a transient one. This in fact is a major problem with most questions along the lines of “what effect will X have on human evolution”; X usually is something that isn’t going to last long enough to matter on an evolutionary scale.

And indeed, expanding on that, the rate at which human society changes, and technology advances, is so fast that human evolution is crawling towards a goal that is moving faster than it ever could, and is accelerating.

I also agree that if we don’t nuke ourselves, technology will probably make the notion of human evolution moot* within mere centuries, as at the very least, we’ll be able to entirely engineer our genome.


  • I know some people here call whatever happens to humans “evolution”, even artificial selection of a genome, but for me this is a misleading use of this term at this time.
    It often is followed by “…so we’ll still be evolving” as though it’s a simple continuation of an existing process.

One side-effect of our huge success in species survival is that we’ve moved the emphasis from survival-based selection to sexual selection. We’re still evolving – to become more physically attractive.

Firstly, as mentioned, if we are evolving we are slowly evolving towards an ever-moving target, for the brief time remaining before we completely synthesize our genome (or just live within machinary) and all bets are off.

But secondly, are you sure that there’s a correlation between physical attractiveness and birth rate? And that that correlation is more significant than others such as wealth or personality traits?

No species ever evolves “to become” something. That is, there is no trajectory of a species evolution that can be predicted over what would be considered an evolutionary timescale.

Except the concept of what constitutes “physically attractive” is almost entirely cultural, and changes hugely from generation to generation and from place to place. Look at the paintings of a few centuries back, for instance. Once again, we’re shifting the target far, FAR more quickly than evolution can keep up with.

Historically the biggest killer of kids was infectious disease and malnutrition. Since breeding age is about 15-30, most diseases of Western lifestyle do not matter.

More than that, the purpose of life is different now. A healthy immune system is overrated in the age of hygiene and medicine. We should be encouraging people would can function in and expand our technocratic society, not people who can survive malaria and zinc deficiency.

The big problem is people who cannot function in developed society have higher birth rates. It applies on an individual level and national level. Afghanistan and Uganda have much higher birth rates than south Korea or Canada. Plus people who aren’t foresighted to consider the responsibility of children have the most. The dumbest people I’ve known usually have the most kids and have them younger. That is the bigger problem. Basically evolution is currently rewarding an inability to plan ahead or get you societies shit together. Evolution rewarding bad health is not the problem, evolution rewarding people who aren’t foresighted, intelligent and responsible while punishing those who are, both individually and collectively is.

Culture definitely plays a part, but I think people really want to believe it is a much bigger factor than it is.
I’m living in China right now, and what a surprise; the women considered pretty here I also find to be pretty, and drawings of beautiful woman going back as far as people could actually draw here also look good to me.
And virtually no culture anywhere would consider say, old age or diseased skin to be preferentially attractive.

Of course, I agree with this 100%.

Heh! Wealth and manners are also probably way up there. All of these are now the mode of sexual selection for people who live in nations where starvation has largely been eliminated.

And arrant stupidity is still selected against, both as a sexual preference (few people enjoy making love to fools) and in the “Darwin Awards” sense, where incredible stupidity leads to accidental death. Death is sometimes nicknamed “The Fool Killer,” and not without reason.

Also…I don’t have to demonstrate that these effects are highly significant; for evolution, it only matters that they exist at all. Even a tiny bias in survival or reproduction is still a forward-propogating differene. (All of which I’m not in a position to document formally anyway, so never mind.)

I don’t know about that; you’re assuming that ugly men and women don’t have kids, which is definitely not the case.

Maybe some sort of Eloi and Morlocks thing is where all this leads, but I doubt it. My guess is that it’s always been this way from the get-go, but that attractive traits don’t correlate nearly so well to things that will help your offspring. In other words, back in caveman days, having a tall spouse with big shoulders, deep voice and symmetrical features meant that he’s likely a better prospect, much like big boobs, a round butt and symmetrical features did for women.

Nowadays, they don’t mean so much in practical terms with the advent of agriculture and sanitation- what may make the difference for your offspring is someone’s intangibles - stuff like family connections, intelligence, chosen career, wealth, etc… that don’t always fire up the crotch so much.

Yes, but evolution does proceed in visible directions. Cheetahs are fast; elephants have long noses; humans have big brains. Humans’ brains have been getting bigger.

I didn’t speak of a “goal,” only of a trend. I didn’t make a prediction.

You are not at all incorrect; you simply are rebutting points that no one has made.