Let’s see, evolution is supposed to do basically one thing: it weeds out mutations which result in a lesser likelihood of survival for the animal that has the mutation, like mutating away the teeth in a crocodile. So you get born a toothless alligator, and before you know it your genes get lost to the pool, because you are one useless reptile. Your brother croc gets born with an extra set of teeth, or claws, or whatever, and he grows to be the strongest of the bunch, survives longest, reproduces more often, and his genes are out there and stay there. Eventually, with a bit of luck, all crocodiles of your species have more teeth or claws, or you develop into a new species – that is, everyone except you, because you died toothless. Bear with me, I’m trying to set the stage.
Correct so far?
Now: there is no evolution in the human species anymore, thanks to the advances of science. First and foremost, it is unlikely that any bodily trait, mutated in any way, will aid the survival of most humans, because they don’t hunt food – they find it somewhere in the worst case, or buy it somewhere in the best.
Thanks to modern medicine, too, mutations will be corrected after birth if possible, or the embryo destroyed beforehand. If a human is born with twelve fingers, and can use all of them (in my opinion a very useful trait in the age of computer typing), that will be surgically corrected. The future holds even more direct ways of halting evolution: if you can manipulate genes, of course people will want to remain as they are today, except they may wish for more hair on their heads and less on their ass – but will anyone say, “give me a third arm, it would come in handy?” Hardly, even if that were the way evolution was going.
So the question is: did humanity stop evolution of its species already? Will it?
(First off, let me stipulate that I assume that we all know that a functional extra arm will not simply appear on a single round of gene mutation and that your further example was simply a way to throw out an easily grasped idea rather than one that we have to niggle over how the change could occur.)
In the example quoted, we already find individuals born with a sixth finger on each hand. (I am not sure how functional they are; I never felt the need to question the one person I knew with extra fingers “Gee, do they work?”) However, surgically removing them (which we do not now do) would have no effect on the inheritance of that genetic trait. If people who developed extra fingers reproduced at a sufficient rate and suffered no other “side effects” from the genetic change, their number would begin to grow within the population.
In the context of a trait that conferred more resistance to bacterial disease or UV rays, for example, such a trait could, indeed, begin to propagate through the population and eventually affect the entire species. Or such a trait may propagate through the species in a sporadic manner, and when we suddenly blew the ozone layer to hell or encountered a sufficiently nasty bacterium, the people who had inherited the trait would be at a great advantage to survive the changed environment.
In one area, we have been messing with humanity in ways that could potentially harm the species. We are using medical science to keep alive past the breeding age people who suffer genetic problems that previously kept them out of the gene pool. Type I Diabetes, hemophilia, Cystic Fibrosis and several other diseases are being “beaten” by new therapies that allow children suffering from them to actually live (relatively) normal lives, grow up, and, increasingly, have kids of their own. To the extent that any of these types of diseases are heritable, allowing such people to reproduce means that there will be a larger percentage of the population at risk for those diseases.
The hope is that gene therapy–in which the actual heritable genes are corrected–will provide an answer to allow those children to grow up without “endangering” the species.
In terms of genetic engineering overwhelming future development: it could happen. However, it is also possible that there will be enough of the apparently “useless” genetic code that we will never fully understand and from which new traits could still arise.
It is a truism within Science Fiction that once we can manipulate individual genetic code, everyone will want to play wild and crazy games with their bodies (or their kids’ bodies). I don’t know that that is absolutely true, but I suspect that it is closer to human tendencies than the idea that we would want to lock ourselves into an “old” mold.
Re-reading the post of BigE, I see I may have jumped to the incorrect assumption that “surgically removed” meant amputated, when it may have meant “corrected with gene therapy.” I think the base of my post still stands, however.
Yes, that was what it was…somehow I suspect that the likelihood of a functional extra arm is fairly remote, given that I don’t know of any land-living animal with an uneven number of limbs. Is there any?
That’s a good one that I had come to think of as well, but thought I’d just not mention so that the the more basic point about visible mutation doesn’t get spoiled…
and also
I find that there are more commonly people who don’t give much of a damn about technological progress and new inventions in general, and new social developments in particular, than there are people who advance the borders of science and society into previously unknown grounds. For one thing, I guess there’ll be a couple of religions who’ll be opposed to changing God’s creation as we see fit; and many conservative people who will think likewise. Will they be dragged kicking and screaming into the age of Genetic Experimentation, or will some humans evolve themselves (and that’s not evolution really, is it, when you do your own evolving?) to create a “super” race? Bit of a hard question, but that’s why we’re here…
Very few people will care about the notion of carrying science into the future. However, look at how popular mere cosmetic surgery and lasik surgery have become in a rather short period. Now what happens when some geneticist hires some jennifer (Anniston, lopez, etc.) to hype what Monsanto or GenCorp could do for you?
(Yeah, there will be religious groups in opposition. Have we made abortion illegal lately?)
I would have to completely disagree. Humans are still undergoing evolution, modern medicine or not.
Evolution is, in the simplest sense, is descent with modification, and that is certainly still going on. In order to stop evolution, each subsequent generation would have to be identical to the previous generation.
In another thread, I wrote a poem about it.
Well, that’s true of any organism… most mutations are probably harmful or neutral regardless of technology.
This certainly can’t and won’t be done for all mutations.
I suspect genetic manipulation will have the opposite effect: it will speed up evolution to an unprecedented degree. People will be able to manipulate the genetic composition of their offspring, and people will make different choices.
In the distant future, it’s even possible to speculate about humans with functional gills or wings, even if it does sound half-baked now, what might 500 years of genetic technology bring about?
Most humans of course live in undeveloped and semi devloped nations without easy access to eevn the most basic medical care and have to work physically hard from dawn til dusk to survive, so that statement is utter crap. 
Hunting is not the only means of obtaining food that requires physical fitness and hasn’t been the primary means of obtaining food for most humans for over 5000 years. An Nigerian farmer does not just find food, she grows it by lugghing water 5 km a day and following livestock over rough terrain 12 hours/day. I wish we all did live in a world where we could just find food, but try and remember most humans aren’t as lucky as you an I.
Even if we’re going to make the ridiculous assumption that no genes are shared between the first and third world the ability to hunt or enegage in hard labour is still a major decing factor in the economic success of most of the world’s population. Most jobs remain unskilled or semi skilled and even most skilled jobs give a distinct advanatge to somone who can walk upright, talk, look reasonably attractive, lift things etc.
Again not even close to being true for the majority of humanity. Most people can’t manage to get tetanus vaccinations, let alone surgery or gene therapy to correct the fairly minor type of mutations you use in your examples.
Short answer: No.
As already mentioned most people are still dependant on exactly the same menatl and physical characteristics they have been for the last 40, 000 years just for survival.
Secondly evolution will still occur until we can eliminate all disease, war, violent death and other selective pressures along with all social inequality. Basically we need to remove everything that could possibly prevent an inividual from producing as many young as possible. If we have a war every hundred years that kills young men before they breed we’ve altered the genetic makeup of humanity. Every disease like aids puts some pressure on teh human population. If AIDS were the only cause of death in humans eventually every human would inherit the genes that make us immune to AIDS. It may take millenia but that slight selective advanatge would cause the gene to spread throughout the world, and we have real evolution.
Basically the idea that evolution has stopped or even slowed appreciably is nonsense. You can only liminate evolution if you eliminate all selctive pressures, and I can’t even conceive of such a world.
My basic understanding of evolution is that mutation is caused by solar radiation (?) and mutations which help a species to survive are passed on genetically to offspring.
I guess the key words are “help a species to survive”.
We developed world Eloi have medicines to help us survive, whereas the underdevloped world Morlocks miss out on those…
So, just looking at that one example, to go along with Gaspode’s comment, should people in underdeveloped nations (if economic boundaries somehow remained static long enough for evolution to occur, which is a nonsense, but anyway) eventually have better resistence to disease than people in developed countries?
On the other hand, if the question is more like “will homo sapiens evolve into a new species”, I’d say that the answer is: possibly, but if so only if there is sustained reproductive isolation for a particular population (ie., some tribe that is completely cut off from cross-cultural breeding or possibly a population of planet-colonizers in the distant future)…I say this because the extent to which humans have overtaken the planet and so freely intermix combined with the way that we manipulate our environment to overcome obstacles (as opposed to being controlled by the environment) would seem to make it difficult for speciation to occur.
Then again, of course, I could be completely wrong.
But all things change. Just wait until an asteroid wipes out 99% of humanity. Or until we start colonizing other worlds (i.e., small, isolated tribes breeding in different environments).
…certainly doesn’t keep his thoughts to himself, does he? But no matter:
That’s not the main point of the question, but note that I said “worst case” and “best case”, with much room in between for Nigerian farmers. In my personal opinion, it is much better to lug water and protect livestock for 12 hours than it is to have to rely solely on what you find – among the trash of cities, or where ever. Might not be your opinion, but it is mine.
True, but bear with me for the purpose of discussion. Reduce the OP to “will evolution in developed countries cease”, or something thereabouts, if you find that a more discussable supposition.
Ah, that’s a good point right there. Of course, I had neglected to consider that nature’s dangers may not be the only selection process. Thanks for the idea!
However, the AIDS example doesn’t fit my OP, since I had stipulated that genetic therapy would be among the causes of the stop of evolution – obviously, genetic therapy will be able to stop AIDS, if genetic factors play into AIDS immunity. Might take time, I’ll admit to you.
Imagination, that’s the key! No, really, you only have to eliminate all selective pressures for which genetic causes are not the key, for you can genetically alter everything else [that is, you will likely be able to alter everything else in some future]; in other words: get rid of war, get rid of hunger, get rid of violence. It’d be said to say that one cannot conceive of such a world, for it should be what everyone should strife for.
An interesting twist to this discussion that you have entered is the part that unnatural causes play in evolution – I’m especially struck by the notion that war plays into evolution. Of course it does, but I had never thought of that. So thanks again for a good thought.
Firstly Big-E let me apologise. I had no idea how gruff that post sounded when I posted. In mitigation I’ll say that I did post it after spending 10 hours lighting fire breaks.
You’re quite right to say that scavenging food on a garbage heap in Brazilia isn’t necessarily a better lifestyle than herding goats in Nigeria. However both still require hard physical labour and both still exert considerable selective pressure on the people involved. The weak will succumb to disease from infected glass cuts in Brazilia and to heat stroke and dehydration in Nigeria but the end result is the same: some genes will enhance survival ability in children. That was my whole point. You stated that “it is unlikely that any bodily trait, mutated in any way, will aid the survival of most humans, because they don’t hunt food”. To give you an example in context of why I reject this: A child is born in Brazilia who has heavily keratinised skin on his feet like crocodile hide. He will suffer from fewer cuts and needlesticks while climbing over the garbage piles and so suffer less diseases, particularly things like tetanus, AIDS and hepatitus that could prevent him from ever breeding. Immediately we have a situation where a bodily trait will aid the survival of most humans.
Now as for whether evolution in first world countries will decrease, in reality the answer is no. As I stated in my first post this assumes that there isn’t a massive interchange of genetic material between the first and third worlds and we know this isn’t true.
Now if you’re going to rule out the IADS example because we could all be genetically engineered to possess only AIDS resistant white blood cells then I don’t follow you. If all humans at some point in the future possess this gene then we have got evolution. The genetic make-up of the species has altered. Just because it’s been done artificially doesn’t make it any less eveolution. Are you in fact asking whether natural evolution can be stopped simply because we can note any beneficial genes and immediately distribute them to the entire population? If so then the answer is yes, but it’s a bit like saying my house is fireproof because I’ve already burned it to ashes. You’re just pre-empting an outcome and declaring the outcome avoided. Not real logically sound.
You then go on to say “you only have to eliminate all selective pressures for which genetic causes are not the key…get rid of war, get rid of hunger, get rid of violence”. Unfortunately genetic causes are the key to war as much as they are to disease. There are a lot of genetic factors that make people favoured by war, or starvation, and there are just as many factors that make people favoured by disease. You couldn’t make a person who is genetically immune to all diseases because the very gene that prevents disease A will grant susceptibility to disease B (as an example it’s thought that the genes that cause aging are designed to prevent cancer). Similarly the very gene that promotes fatigue resistance in war may well be the one that slows reflexes. That’s why humans have such a wide genetic make-up. We have some individuals who will survive any situation they encounter, but no individual that will survive them all. Gnetic engineering may enable us to produce humans that are optimised for life in Montreal working as surgeons, but such people won’t be optimised for life in Nairobi working as gardeners. Completely different environmental pressures. The only way to optimise humans (or any other species) completely is to equalise the environment and eliminate all inter and intra-species competition. That may be theoretically possible, but the organisms that you’d have, by not engaging in any competition with each other, would no longer meet the definition of human. As such you’ve defeated yourself by forcing the entire human race to evolve into something no longer recognisably human.
So in summary.
Has human evolution stopped: No, not even close
Can human evolution be stopped in the conceivable future: No
Can human evolution be stopped in the dim, distant future using any technology that we know of or could even imagine today: No
the chemical environment is also a factor in causing mutations. I don’t know the proportion of radiation-induced to chemical-induced mutations.