zen_tom

In another thread, there were some suggestions to the effect that, man, having invented hospitals and medicine etc has effectively stopped the march of evolution.

I'm not entirely sold on this idea, since I think that selection criteria play more of an important role in evolution than the old 'fittest survive' notion. By selection criteria, I mean what men find attractive in women and (perhaps more importantly?) what women find attractive in men.

In the west, many people would only consider having a child in a very strict set of circumstances, with someone they feel is 'right'. (There are of course, many other people who don't apply these criteria)

If our pre-disposal to good personality, bone-structure, intelligence, social abilities etc is part of our sexual selection process, then both these traits, and the preference for them will likely be passed onto our children.

This double-hit, if anything, might be accelerating our progress down the evolutionary path. Some recent scientific claims (that I will try and find a link to at some point) suggested that from the outset, man has evolved and changed at an unprecedented rate compared with other creatures - perhaps this is likely to continue?

Anyway, I wanted to hear your thoughts. No doubt, the idea of technological enhancement of the human/body/brain could be said to be an evolution of sorts, as could the idea of the creation and development of intelligent machines - but if possible, lets try and stick to natural evolution of people over the next few thousand years.

noodles

evolution's not dead

sure, it might be slower or smaller because of what we have going on now, but it still happens. just because we're not evolving obvious body adaptions like a large beak to crack open nuts doesn't mean that they're not happening on some level.

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flstf

I believe that the natural selection process and thus the gene pool is being altered dramatically because of our medical progress. People who not so long ago would have died before they could reproduce are being kept alive now and passing their inferior genes on to the next generation. I'm not saying this is a bad thing just pointing it out.

Like one of my high school friends used to say, "we have a natural selection process going on here, the football players and the cheerleaders always seem to wind up together".

Charlatan

Natural selection has been greatly affected by the fact that we have cured or have managed many diseases and disorders...

That said, we are rapidly entering a phase where we are taking control of the process of evolution. Right or wrong, for better or worse the pandora's box of genetics has been opened. In time we will be able to modify ourselves in some very interesting/horrifying ways...

Add to this the fact that machines have already altered the way in which we interact with the world... Everything from cars, planes, stand mixers, computers, etc. Have and continue to have an effect on how we develop...

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sapiens

I agree. Sexual selection is still operating in human population. People are not mating indiscriminately. If those traits by which people preferentially select a mate are at all heritable, evolution will occur.

Another important consideration to keep in mind: present day is just a blip (not even a blip really) in human evolutionary history. Even if evolution has "stopped" in human populations (which I seriously doubt), it has't stopped for very long.

raveneye

To paraphrase your argument using biological terms, human technology has reduced the importance of "natural selection" because it has reduced the importance of external natural forces on human survival and reproduction. However, technology has done nothing to reduce "sexual selection" or female mate preference or male-male mate competition.

I agree that sexual selection is just as strong in humans everywhere as it was a million years ago. But natural selection has weakened only in developed societies. In undeveloped societies mortality rates are still very high and probably influenced by genetic traits such as disease resistance and behavioral traits related to social dominance.

Charlatan

Are you suggesting that humans in "underdeveloped" parts of the world will evolve differently than those in the "developed" parts of the world?

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sapiens

Individuals in "underdeveloped" parts of the world are likely exposed to different selection pressures than those in "developed" parts, but I would guess that there is too much gene flow between "underdeveloped" and "developed" populations in the present day to expect divergent evolution.

C4 Diesel

A little off... Medical progress doesn't change natural selection in the sense of it changes the selection criteria... It DOES AWAY with selection criteria, which stops natural selection and thus the gene pool would not change under those circumstances.

To those who say sexual selection are causing evolution... Yes, people have preference, but people define sexual standards for themselves based upon their own fitness (in this manner "fitness" denotes the overall quality of the individual based upon species-based sexual preference). People who are less fit will accept a mate who is corrspondingly less fit. Therefore the less fit also reproduce. (how many people do you know that suck at life so badly that they, not by their own choice, will never be able to marry or have kids?)

And to Tom's question... The conditions required for no evolution are scientifically defined. It requires:
1) no selection pressures
2) no population isolation
3) no random mutation within the genome

The last condition cannot be satisfied naturally, so there will always be evolution, by chance at the very least.

However, to people that say sexual selection does affect the genepool, I will offer you this... While the less fit do reproduce, they very infrequently reproduce with the more fit (not too many people who are ultimately attractive, have great personalities, and are supremely intelligent with mate with anything much less than themselves). You could possibly make the argument that this creates sexual isolation of the two "populations". However this would be a difficult case to make because it requires very little interbreeding to bring a population's genepool to the species average.

. . . I teach this stuff to college kids. Haha...

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raveneye

Actually C4, one could argue that sexual selection is currently having a greater evolutionary effect than in the past because it is no longer held back by natural selection, at least in developed societies.

Anybody want to suggest human traits that probably evolved by sexual selection? Here are some possibilities:

--many racial differences in facial features (no adaptive value, however certainly important in sexual attraction)

--sex differences in voice pitch

--sex differences in size, muscle mass, hair

--fat content in breasts in women (no adaptive value, but apparently important in sexual attraction . . . . )

Charlatan

You also need to remember that things like modern transportation (i.e. stream trains to the airplane and automobiles) have drastically effected the diversification of the gene pool.

Intermixing between nationalities, let alone village to village has greatly increased since travel and immigration has become more prevalent.

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wilbjammin

Since social status is a huge part of what humans consider to be desirable traits, and because social status is largely a media construct focused on wealth - natural selection is a concept that is outdated.

People do look for desirable traits, such as symetrical faces, good hygene, etc. But, in general, fitness is not something that comes in play as much as it used to because it is not necessary. Look at those suffering from bulemia and anorexia or extreme obesity that find partners. Now there is a larger variety of what can be found that is survivable for humans, so the umbrella is getting larger.

What I consider to be odd about this is how much emphasis is put on these discussions of (big E) Evolution. Focusing on evolution seems to put the emphasis off of the fact that the primary responsibility that we have as individuals and society is to lay the groundwork for the generations that come after us. If we care about "evolving" as a society, or as humanity, then we need to pay close attention to the opportunities we create for ourselves through economic policy, access to resources, polution and climate issues, and what causes death of anything in the cycle of life (war, fires, land management, floods, etc.).

We have a lot of control of our fate as humans, to look at a broader evolutionary picture of humanity is bound to (ironically) leave us very short-sighted.

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bingle

I think it's definitely true that we've affected natural selection, but I just can't agree with the idea that we've somehow transcended nature and evolution.

After all, the reason humans have been so successful as a species is our brain. It's better than having the sharpest claws or the longest beak, but it's still a naturally evolved tool. Now we're simply using that tool to the best of our ability in order to help our species survive.

Saying that by doing so we've stopped evolution or natural selection is like saying that turtles have stopped evolving, because even the sick or weak ones are still protected by a hard shell.

There's a tendency to think of things produced by our brains as separate from the natural order, but in reality it's just like beavers using their enormous teeth to build dams. Our tools affect our environment on a much larger scale, but all we're doing is utilizing the tools evolution has given us.

Of course, it may turn out in the end that we're an evolutionary dead end, and that we've used our tools to destroy our environment to such a degree that we select ourselves out, but even that will be a part of natural selection. Or it could turn out that we standardize our gene pool to such a degree (by removing some of the pressures of selection) that we'll be unable to adapt to changing conditions and just die out. It will suck for us, of course, and for many other species, but it's still a part of the evolutionary process. Even if we wanted to overcome natural selection, we'd be unable to.

Bingle

Yakk

Family planning is a selection criteria.

Stable societies that aren't awash in mass violence is a selection criteria.

First, you are assuming a very strong correlation between parent and child fitness, for two seperate pools to form.

Second, people change. At 13, that eventually supremely intelligent, ultimately attractive and great personality person might knock up the ditzy cheerleader, or be knocked up by the football quarterback.

And this trumps all the other arguements.

I was once worried by possible genetic drift of the human race into strange places, caused by our lack of 'survival-traction', on a genetic level. But very shortly people will be picking what genes go into their children.

The power, scale and impact of this will make sexual selection look as important as cosmic background radiation is currently to evolution.

To take a possiblity from RAH, even if all you did was select which of your own genes get put into your progentety, the impact would be huge.

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zen_tom

I doubt this will ever be the case, it will always be cheaper and easier to have children in the natural way, without resorting to fiddling about with genes etc. Screening for various diseases etc may be viable, but again, I don't see that having an effect, except perhaps by narrowing the ranges of diversity in the population.

Halx

At the very least, if we cant continue to get stronger and more adapted, then we will continue to get smarter and more capable. Cut off one path and we will go in the other.

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Yakk

When we have reliable in-vitro pregnancy, it will be easier to have children the non-natural way. There are ... species survival problems with that.

Lets assume we have the GeneBlaster 2000. You put a drop of blood onto a sensor, and it takes your genes and quickly generates a chromosome map.

A certain percentage of your gene's will be 'known' to medical science. The GeneBlaster 2000 will look up those gene's online (or in a local database), and tell you which chromosome they come from, and what the suspected and known effects of that gene are. More importantly, it can tell you what the difference between your two chromosomes are.

So, now you have a system that tells you, roughly, what the effects of given random chromosome is. (very rough, however).

If you make a child with chromosome17a, they'll end up with 5% more muscle mass than chromosome17b, on average.

Now, all you need is the ability to sort sperm or eggs based on having chromosome17a vs chromosome17b (which people already do for male vs female sperm), and for it to be cheap.

Raising a child costs as much as buying a home. Westerners spend alot on children -- a small enough pre-birth cost that could have a large impact on your child will be used.

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CSflim

The real question that is being posed is, 'Is the level of selection pressure significantly high?'

To us in the developed world, it would seem that it is very low (‘selection pressure’ is strongly correlated with ‘death rate’). In order to debate about this, we need to consider the people who are not successful in passing on their genes (having children). The most common cases seem to be:

Personal choice: Is this a genetically controlled trait? Certainly not! However is there a genetic component that influences this decision? Perhaps; say, genes that result in independent thinking, and going against social norms. But it seems that people who choose not to have children form a very small subset of the people who show these much more general traits. Alternatively maybe there is no genetic component affecting the decision at all. Nature vs. nurture abounds.

Unfortunate Events: Victims of sheer bad luck and circumstances beyond their control who die before they pass on their genes, e.g. a car crash. There are no genes for good luck, so this will not be affected by evolution. I would also include deaths resulting from war in this category.

Disease: Most terminal diseases affect people only when they are older. So these will not significantly affect evolution. However diseases that strike young people also are significant. If there is a genetic predisposition towards these diseases then evolution will strive to reduce and/or remove this predisposition from the gene pool. However the speed of this depends entirely on how widespread the disease is. It will probably be very slow. In comparison the diseases themselves may be evolving if they are caused by viruses or bacteria, and they will do so at a much faster rate.

Impotence: It seems that impotence is covered by what I said in "Unfortunate events" and "Disease". As far as evolution is concerned, impotence is equivalent to death. If there is anything genetic that affects impotence, this could be selected for/against.

Failure to find a mate: This has been the situation most eluded to in this thread. The significance of sexual selection entirely depends on how many people there are who go through their life and fail to find a mate. It is not obvious that this number is significantly high. In such cases it is likely that it is a result of being "too picky", and so this trait may be selected against.
Much has been made of how intelligent/successful/beautiful people have a tendancy to mate with other intelligent/successful/beautiful people. But don't forget that unintelligent/unsuccessful/ugly people also mate with each other. So there is not necessarily a selection pressure due to this 'caste' system of mating. The idea of divergent evolution is ridiculous in this situation as 'intelligent', 'successful' and 'beautiful' are not nearly sharply enough defined and there is enough cross-breeding to keep the species together.
If being unintelligent, unsuccessful or ugly is in-of-itself hazardous to the health then this will effect natural selection directly rather than via sexual selection.


Have I missed out on any? In areas of the world where the death-rate is higher, then the selection pressure will also be higher, resulting in faster evolution. It has been suggested that a genetic resistance to AIDS among prostitutes has been evolved in Africa. (I can't find a reference for this, but I seem to remember reading it some time ago. Can anyone confirm this?).

It is too easy to merely shows ways we can evolve. In doing so, you must also show the ways that we die (childless).

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C4 Diesel

Holy jeez, I have a lot to reply to...

Not a chance. People with small breasts don't reproduce? People with less desirable facial features don't reproduce? That may be the societal preference but these people still reproduce and thus the genepool is not directed regarding these traits, making any sexual selection unrelevant with regard to them. Also, vocal differences and body structures are a result primarily of natural selection. Voice so the genders can recognize male from female (and thereby recognize possible rivals / mates). However while people may have a sexual preference for a certain body type, others still reproduce.

I think some people are confusing sexual selection with sexual preference. Just because you would like to have a mate with certain traits does not mean that those traits cause sexual selection. In order for sexual selection to occur, the other (negative) traits must correlate with less reproduction due to the inability to find a mate. Like I said previously, very few people are so undesirable that they can't find anyone to have kids with. This happens primarily because our genetics tend towards a 1/1 male/female child ratio and our society is monogamous.

This can be a correct statement, but I believe you have the wrong idea. Interbreeding among populations may cause genetic diversification at the level of individual populations (eg. an isolated tribe), but as a species it actually causes a sort of averaging-type effect which reduces diversity. Introduce enough of the rest of the world's genepool into that one population, and soon enough that tribe will be a lot more like everyone else.

Physical fitness is not what I meant. I meant fitness in the sense of reproductive success. In this sense, fitness is defined as and increase in adaptation to the environment, as brought about by genetic change. Therefore, a greater degree of fitness causes those creatures to survive (be "naturally" selected) and mates look for the traits that are a sign of fitness (hence they are "sexually" selected).

However, this is exactly my point that sexual selection really does not come into play. Even the seriously ill find partners.

A sexual preference. It does not cause sexual selection.

In the sense that genocide erases populations, yes. But this is a human-induced, conscious event. I believe the issue at hand was whether evolution was still naturally occurring, and I do not consider warfare to be a natural event.

Well, the assumption is that the parents traits will most likely be passed on to the childern, but yes, it's not so simple. That's why I said you'd have a tough time defending that position, and I didn't really try to.

Lastly, I agree that soon enough we'll be genetically engineering ourselves at a rate millions of times faster than what would ever happen naturally.

Whew... I like it when you guys make me think. It's so stimulating.

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CSflim

Good post Diesel. You cleared up much of the conceptual confusion many seemed to be having.

However, you then state:

What is a natural event? Ants engage in war. Is this unnatural too? Or only unnatural when humans do it? Why the distinction?

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flstf

I don't understand. If people who would ordinarily die from disease before they are able to reproduce are now kept alive to reproduce won't they pass their weaker immune systems etc..on to the next generation? As an example if we save the half million children listed below with early medical treatment won't they pass on their weaker genes?

zen_tom

I'm interested in the idea that selection (of a mate) is more important than fitness (for reproductive survival) Something I read about Peacocks made me think about it.
A Peacock has a huge, beautiful tail that seriously hinders its movements, making it an easy catch for predators - however, because the Peahens like Peacocks with big tails, their chicks who will grow up to have big tails (and the preference for big tails) This feedback loop of genetics creates, in the case of the peacock, an extreme body shape - similar things occur in other fowl, insects etc, but often the most extreme body forms relate in part to quality/preference pairings.

The quality/preference pairing might provide a stronger force in evolutionary terms than the speed, tooth sharpness, or other food-related survival of the fittest elements. When we think of evolution, we tend to think of lions chasing gazelles and as a result the lucky lions parent stronger progeny, while the escaping gazelles do the same. But this quality/preference thing to me seems like it could be a much more powerful influence (especially in reasonably 'comfortable' environments)

If that's the case, it could explain the rapid evolution of our species, and mean that without genetics etc we may still be in a period of rapid development.

tecoyah

I am of the opinion that physical evolution is only discernable in time frames bordering on the hundreds of thousands of years, with occasional jumps that can be seen in the thousands. I do see a technological form of evolution taking place now, which is somewhat evident when one looks back over just a few centuries.
Perhaps the term techolution would be a fitting description of the current path of our species.

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Yakk

Counterexample: Dogs.

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tecoyah

Humans engineered dogs....unless you consider intervention a natural form of evolution, this is a relatively null point.

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Pacifier

If there is a strong selective force pressure on a certain species it seems to happen faster. I've read an article about a snake in australia which changed in the last 70 years (20 generations). It faced the Cane Toad which was bought to australia by humas. the toad is poisonous. so the snakes head became smaller so it only can eat smaller toads (less poison), also it became longer (more "body volume" to dilute the poison). This, small, evolution happend in only 70 years.

http://www.abc.net.au/science/news/e...sh_1250708.htm

But like I said there needs to be a strong selective force, humans are no long under such pressure I think. So such fast evolution seems inpossible for us. But since we are so impatient perhaps we should start our own evolution when we have understossd the mechnanisms and genetics?

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CSflim

Are you refferring to <A HREF="http://en.wikipedia.org/wiki/Eugenics">eugenics</A>?

You must consider what this means in human terms; the sterilization (or murder) of those who are considered "unfit" (by whatever metric).
Though perhaps the ends are admirable (maybe), I really don't thing that it justifies the means.

If you are not suggesting eugenics, then what are you suggesting? Genetic engineering?

(I almost ended the thread via <A HREF="http://en.wikipedia.org/wiki/Godwin's_law">Godwin's law</A> in reply to this post, but quickly came to my senses)

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raveneye

Of course they do. But reproduction is not all or none. If there are any small differences in reproductive rate, and if those differences are correlated with heritable traits, there will be evolution as a result.

There are many human traits that clearly have been influenced by sexual selection, I don't see that as at all controversial.

flstf

Sorry for the threadjack.
Thanks for the link. I must be really new at this messaging debate game. I have been shot down by the old Nazi/Hitler reference several times on these forums. Didn't know I was a victim of this law.

CSflim

You make a correct point, that 'fitness' is measured not only by the ability to sucessfully reproduce, but also based on how many times reproducution occurs. But it remains to be shown that women (or men for that matter) with socially desirable qualities reproduce more often than others. It is possible that they have sex more often, and with more partners, but with the widespread use of contraception, maybe this point is rendered insignificant?

People seem to be working off the assumption that social status is equivalent to biological sucess. This was undoubtedly true years ago, but is it true today?

It is not outrageous to suggest that the number of children a person has is not positively correlated with intelligence, sucess or beauty. It is also plausible that it could be negatively correlated. On the other hand it may not be correlated at all. All three possibilities are open.

What we really need to see is statistics on this topic. Since 'intelligence' and 'beauty' are far too vague, 'sucess' judged via wealth might be a useful metric.


Do not forget the topic of this thread. We are asking whether evolution is going on right now. I am not casting doubt on sexual selection. Large female breasts are quite likely the product of sexual selection opperating in the past. Nor am I casting doubts on the fact that evoltuion is still happeneing. It most certainly is. I am just wondering in what manner is it occurring, and at what speed?



EDIT:This post has been significantly edited for clairity, as people seem to have misinterpreted my intentions with it. I believe that it now gets accross its point much better. I hope that this is not considered dishonest. I am not trying to "cover up" my mistakes, just clarify my intentions.

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C4 Diesel

Here I go again...

Allow me to explain a little better. War is natural. War on the scale that we have it is definitely not. A plane flying over and dropping a nuclear bomb (or hundreds of other bombs) is not natural. Although the idea of warfare is seen (albeit rarely) in other forms of life, we wage warfare using products of technology which are not natural, and makes our wars unnatural. Also, other animals do not consciously commit genocide (the best known way of cutting down on aspects of the genepool).

Yes, they will pass on their genes. This is why the genepool is staying the same. If they died and did not have children, the genepool would change (theirs would no longer be in it). But since their genes are in it now, if they have children the children carry their genes also, and the genepool does not change.

It's not that the tail is more important than fitness... It's an INDICATION of fitness. A tail costs a lot of energy to grow, slows the bird down. Therefore it takes a very fast, strong peacock to outrun predators even with the large tail, and it also means the bird is well fed since it had that extra energy. Therefore it actually helps the peahens select the most fit peacocks.

Although this is a matter of opinion as much as anything else, I would say no. The reason for that is even under many selection pressures, we still cannot evolve faster than our genes can mutate. This being the case, and with the generation time ever increasing, natural evolution is a slow thing for humans.

I like the point you're making how the amount of sex doesn't correlate to the amount of offspring. Also, the alleles (traits) are not evenly distributed. Someone with a great personality might have small breasts, but you don't care because she has a great personality... Or a very attractive male could be dumb as nuts... Because the alleles are so spread out in the population, it's very hard for sexual preference to translate into sexual selection. Reproduction is, in this sense at least, somewhat random.

Oh, and the reason large breasts used to be a sexual preference is also because it is a sign of fitness. Those large fat deposits mean the female is well fed and therefore more likely to be fit.

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CSflim

This is a point of contention and is not accepted across the board by all biologists.
I am not an evolutionary biologist, so am not really qualified to comment on it, but I must say that I find it a bit far-fetched. I find 'memetic' explainations of sexual selection very useful.

Regardless, just to ensure people don't consider tentative hypotheses as on the same ground as established science.


Evolution happens at a faster rate when the selection pressure is high. Although the mutation rate is, in principle, a limiting factor, in almost all cases it is the selection pressure that determines the speed.

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raveneye

I have no doubt that evolution is going on right now in the human population, nor do any other evolutionary biologists that I know of. Evidence of traits evolving by sexual selection in the past certainly is pertinent to the question of whether a similar process is currently operating.

Your points about contraception are well taken. However, as I said previously, very small differences in reproductive rate are all that is necessary to produce large evolutionary change even over the medium term. Anecdotal stories about behavior of acquaintances aren't really convincing in either direction.

CSflim

Which is why I made absolutely certain to portray them exactly as they were("In my experience", "my own subjective interpretations of", "perhaps"), and on the very next line wished for statistics on the subject, even going so far as to state how they could be measured.

My point was that the 'obvious' fact (social sucess = biological sucess) might not be necessarily true.


EDIT: Also, at no point did I state that evolution is not currently happenning. I was merely examining the proposed mechanisms by which it is supposed to be happening.

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C4 Diesel

True, it is a hypothesis, but how are you going to prove it? The only thing provable is that females like the males with big tails. You can't ask the peahen what it thinks. Fact is, it does take a lot of energy to grow and only strong, fast peacocks can avoid predation because of it. From the standpoint of selection pressures, there would be no such pressure for a female to evolve to desire a mate with a feature that merely acts as a hinderance (which is what it is doing if she just wants the tail because it's pretty). The only way that this could be taken as an indication of fitness is because the bird wants it to be. On the other hand, it being an indication of fitness makes it easy to see what male has the best traits. I'm not saying that one is definitively correct, but I think theres an answer that definitely makes more sense.


Where are you getting this idea from? If mutations occurred faster than the selection pressure could be applied, then there would be no extinction from predation. This is like saying organisms are able to adapt faster than they could be killed from a natural cause, and it simply is not true. If it was, why aren't all animals on the African plains that are hunted by cheetahs able to outrun the cheetah? And if they became too fast for the cheetah, why would it then not become even more fast to avoid the starvation of its species? The situation of the limiting rate being selection pressure would put evolution proceeding at a rediculous rate; one that the mutation rate would have no chance of keeping up with.

Mutations occur very, very seldomly (in the sense of mutations / base pair replicated) and are completely random. The genes don't get up and say "we have a pressure, here... we need to do this". It's all just chance, and some chance works out better than others, and chance takes a long time until you reach something meaningful... Similar to the saying about an unimaginable amount of monkeys with typewriters would eventually create a work of Shakespeare.

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raveneye

Well I certainly agree with that, but that doesn't imply that no evolution is happening currently. There's no doubt that it is. Whether anybody would call it human "progress" is a separate question.

CSflim

Discussion of this, while interesting is well beyond the scope of this thread. I was not attempting to counter your argument (in retrospect I should have left out my own opinion on the matter). I merely wished to point out to others reading that this was not a hypothesis accepted by everyone.

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C4 Diesel

I just realized something... If we really are just arguing if evoluton is happening or not, then I think we've come to the conclusion that it has. Although we're debating the rate of evolutoin and if/what selection pressures still apply, no one has (and I don't believe anyone can) said anything about the ceasing of random mutations, which is a requirement for a condition of no evolution. Therefore, unles someone can say something against this, I conclude that we have concluded that there is evolution happening.

. . . Now I'm gonna go watch Tilt. I'll catch you guys a little later.

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CSflim

I clarified this in an 'edit', which was too late!
I believe we are currently evolving. I think we are doing so quite slowly in comparision to much of our past, but we are definately evolving. The aim of my posts have not been to show that we are not evolving. I was merely examining the proposed mechanisms by which it is supposed to be happening.

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CSflim

You've got it the wrong way around. Those are a list of necessary conditions, not sufficient conditions.

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