What is the effect on the human genome over time of saving unhealthy children?

Does the human genome become weaker over time until most kids need some kind of intervention to be saved, or is the effect of saving super-preemie babies, kids with chronic, genetically mediated diseases, weak immune systems etc, etc, irrelevant in the long run?

In other words, in the past nature selected for hardier and more fit humans by killing those that could not survive. Now we have lots of people walking around and making babies that would have died without medical intervention. Is there some real price to pay somewhere down the line re the hardiness of the genome, if less healthy people propogate in much greater numbers than before or is this a non-issue geneticallly.

As a side question, if we acquire the ability to re-write a person’s DNA in utero at some point in the future, will this whole issue become moot?

Do keep in mind, natue has a tendancy to preserve what we would view as weakness (say, sickle-cell anemia) in recessive genes, just in case a plague of malaria occurs.

Besides, hardier != well-adapted. If a person can hunt but not read, would they be considered as a mate for many of us?

There is no real measure of genome “strength.” In general, the only thing evolution cares about is fitness. We currently live in an environment where patients with sickle cell disease or cystic fibrosis do not have the drastic reduction in fitness they did when we were hunter-gatherers in Africa. These people are now fit to reproduce – in this case it is the environment that has changed, not the genome. If the environment were to change again (i.e. all hospitals were blown up), they would cease to be fit again.

If you actually go and figure out the allele frequency of things like CF and SCD, something becomes apparent immediately. The heterozygous frequency is huge – CF is carried by 1/25 people of European descent and SCD by something like 1/7 people of African descent… I don’t feel like Hardy-Weingberging the numbers right now (figure out q[sup]2[/sup] when 2pq=1/25 or 1/7 and p+q=1), but the percentage of homozygous individuals is tiny compared to this. Therefore, most of the allele contribution to the gene pool is by asymptomatic carriers. This applies to more rare conditions as well – you find often hundreds of times more heterozygotes for a disorder than homozygotes. In short, is why eugenics doesn’t work – you can’t do anything by selecting against the homozygous affected individuals and if you plan to select against heterozygotes, you will find that a startling number of people will get selected against.

As for your second question, it is hard to predict given the modalities of gene therapy currently being pursued. But in all probability, yes.

I think that keeping the weak and sick alive and viable will have the same effect on humanity as on any other population. It will eventualy make the population at large physicaly weak. I dont think it will matter much because people can compensate with machines. Then again , what happens when the lumberjacks and longshoremen have all been replaced by their less able counterparts? Who will build things when it is harder for people to do a “hard days work”? I have a theory, but since I am no genetic expert there will probably be a few flaws in it. I think you can look to the conflict in Afganistan to see some of the results already. Your average Afgani fighter wears the same style jacket shirt and trousers year round. The soviets on the other hand were stopped by the cold weather in Afganistan. Is this because the Afgani people are better acclimated to the climate or is it because with their generaly low level of technology only the strong can survive there? The soviets have bitterly cold winters as well , so I dont think it was just the weather. The only other thng it could be is that more of the weaker genes were bred into the population of the soviets due to their higher levels of technology. More of the weaker genes survived and continued to be passed on, resulting in weaker people.


It probably “weakens” the gene pool to some extent. However, it will not be long (certainly within 50 yrs) before we are able to alter our DNA to such an extent that many or most of those “bad” genes can be eliminated. We will also most likely be able to manipulate our genes to such an extent that some individuals will essentially be differnet species (unable to reproduce traditionally).

Obviously these techniques won’t be available to all 10 billion or so humans on the planet in 50 yrs, but I think the effect of genetic engineering will dwarf any “weakening” of the gene pool.


If we are all engineers and none of us construction workers, then we will build better tools. Not a bad thing, as I see it. But I’ll bite: Under what scenarios is human strength, speed, endurance not replaceable by machine strength, speed, etc.?

How can we build better tools if we are too frail to lift them? If the recessive genes become the dominant genes then humanity could all end up like Stephen Hawking. Smarts are great, but what good does it do you to be smart if you cant wipe your own ass? On the other end of the spectrum, we could all end up physicaly stong, but mentaly deficient. What good does it do you to be as strong as an ox , but too dumb to even realize that you have an ass to wipe? Then there are the carnival “freaks” like the wolf man and flipper boy. THey are pretty normal, but they have congenital disfigurements that will make life difficult for them. What good is it to be trapped by a bodie that is just non functional.


Perhaps you ought to ask someone who does have a physical handicap/deformity if they’d rather not be alive. Hopefully this doesn’t sound too reactionary to you, but implying that there’s somehow no satisfaction to be had by a person in a body that’s less than perfect (however you’d define that) is pretty ignorant, and flat-out wrong. Maybe, though, that’s not what you were trying to say.


Evolution doesn’t work like that. Recessive genes cannot become dominant. I’m guessing you knew that and meant infrequent genes become the norm. But that would only happen if those “infrequent” genes provided a survival (reproductive) advantage. Hos would that happen? You could argue that the invention of agriculture allowed some people to survive who would have died as hunter gatherers. Did this hurt the gene pool? Hell, you could argue that the first hominid to chip a stone tool allowed some of his fellow hominids to survive who would have died if they had only their bare hands to work with.

It just doesn’t make sense to worry about “weakening” the gene pool. Especially, as I said above, when we are on the verge of being able to manipulate the genome at will. Mistakes in genetic engineering are more scary to me than the fact that “weak” children survive today.

I guess you missed my point, Eonwe. I am not saying that people shouldnt live, or wouldnt want to live, but what if eveyone were born deformed. That was the point I was trying to make with the whole post. What if deformitys and defects became the norm. How self sufficient is someone who can not do the most basic things for themselves. Now what happens if everyone is like that, so that there is no one to help because the can barely help themself.

for John Mace , Nope I didnt know that. I only know what I read and see on discovery and TLC. I remember reading about how they can get fruit flys to hatch without wings after a few generations. I dont see why something like that couldnt happen to people in a some what longer time span.

Ah… so in some distant distant future, what if everybody is born with vestigal arms, for example?

Do you really think we would get that far? I think the odds of that are quite low. What indications are there today that people are going to stop being able to function in any way as a result of technology. Perhaps there will be no more lumberjacks, to use your example, but if I were to decide to be a lumberjack and get all buff and strong, I’d have just as much a chance of passing on “physical strength” genes as if I sat at a desk pushing buttons all day.

That’s an awfully big “if”, of course.
Recall that there are a number of factors at work in determining whether a gene will get passed on to future generations. First and foremost, the individual has to be able to reproduce. This means being able to survive to a sufficient age (which, with modern medical technology becomes more likely), but the individual also has to find a mate. If the Stephan Hawking look is a big turn on for most members of the opposite sex, then one might well expect the frequency of such a condition to rise. If it isn’t, then it likely won’t.

If a particular allele does not result in any noticable physical difference, then it may have a higher chance of being passed on (again, assuming it does not otherwise adversely affect the individual’s ability to reproduce). An increase in frequency of such alleles may well eventually make humanity more dependent on proper medical care – which essentially represents a specialization to a given environment. Such a specialization may make us more susceptible to extinction, but do not automatically doom us as a species: one of our strengths as a species is our ability to continually modify our environments, rather than simply respond to changes in them. So long as we can continue to do so, such a major shift in the genome will likely have little overall affect.


You have to be careful about extrapolations. You cannot take an isolated issue (like a few “deformed” individuals) and extrapolate out to infinity assuming that nothing else changes. For example, if there were a “deformity” that required someone to be cared for constantly, and if that deformity occured in, say, 75% of the population, those people would start dying off since there wouldn’t be enough people, as you said, to take care of them. The population would tend to stabilize at some level below 100% occurance.

Think of the balance in nature of predator and prey. You cannot affect one population w/o affecting the other.

But let’s just say that you were correct. That the gene pool was being destroyed by recessive genes. What would you propose? Eugenics?

The only thing I can see is that the species adapts to the environment. Our present environment includes sophisticated medical care. Should that become unavailable, those who would live only because it, won’t.

I don’t see the evolutionary problem.

Wasn’t that what happened to H. G. Well’s Eloi in The Time Machine?
If you by weaker mean less fit in a Darwinian sense, then probably not – since what made us fit 100,000 years ago, is not necessarily what makes us fit today. If you by weakness and strength mean the ability to survive in a natural environment without the help of technology – then yes; short circuiting natural selection will make the gene pool weaker (less able to cope). However it is questionable weather natural or sexual selection has much relevance anymore (I don’t really buy into the argument that it’s still just natural selection in a new environment). But I think it must make us pause if it turns out our personal physical survival or reproduction is increasingly dependent on technology. If we’re first on the tiger’s back, it can be very hard to get off.

Naa. Nature does not make plans for the future. If genes exist in the gene pool, it must be because they offer some advantage now, or because nature hasn’t kicked them out yet. Of course, if they’re recessive, they’re likely to hang on for a longer time, but if they truly have nothing positive to contribute to the whole organism – out they must go eventually.

This is a hard question; perhaps you could give us your best answer too. There are some words that are surrounded by such a degree of controversy as to nearing taboo – eugenics being one of them of course. And you suggest (I may mistake your sentiment) that such actions would always be out of the question, but if, for the sake of argument, the human species was truly in severe danger (are there any other kind?) would you sacrifice the species for the individual?

> Stephen Hawking
BTW. Hawking had a very nice wife (I think he divorced), and at least two children, how they fare I know not.

Let us not forget that we have made great strides in understanding and diagnosing genetic diseases to the point where a simple blood test can determine in advance the chances of passing on something like cystic fibrosis or sickle-cell anemia, as well as in-utero tests. Armed with information a couple can choose not to have a child or (and I really don’t want to get into this can of worms) terminate a pregnancy. Wouldn’t this have the effect of “strengthening” the gene pool?


I don’t really have much to say about Eugenics. My comment was specific to Burner, who would not let go of the idea that we were all headed down the path to ruin. I didn’t understand his point and since he didn’t seem to understand what I was getting at, I wondered what he thought we should do about it.

I would take a pretty libertarian attitude toward eugenics, I suppose. I can’t image a realistic scenario where it would make sense to sacrifice the individual for the sake of the species.

Actually, couldn’t you make the opposite case-that human beings are becoming MORE fit and stronger today, because of modern medicine, nutrition, better living conditions?


Yes-- our exploding population proves that point. We have taken control of our own environment to a great degree.

Yes, if you define humanity to include its technology. But because of the comfortable conditions that we create for ourselves our bodies may end up losing their general-purpose toughness. We may become increasingly vulnerable to anything from which our technology cannot protect us.

Looking on the positive side, perhaps advances in genetics will give us the ability to correct any serious deficiencies in ourselves should any genetic deterioration cause us problems in the future.

However we are becoming less and less able to even survive as a species should civilisation collapse and we lose our technology.