Does natural selection still exist in humans?

[Go Blue]

Let's keep this just confined to developed nations. I was thinking about this not too long ago. It seems that in today's world, most genetical disadvantages that people have don't really matter and thus they won't be selected out by natural selection. There are a few exceptions I think, but with modern science, it seems that almost everyone can reproduce and pass on their genes. Thoughts?

[hmkpoker]

The principles behind natural selection still exist, so we are still "evolving"...it's just more likely that the social/technological effects are going to have more impact than natural selection. But yes, human society develops so much faster than evolutionary effects that I don't think they'll matter much.

[Go Blue]

Right, I know we're still evolving but I was questioning whether there is natural selction. It just seems to me that any advantages that people may have don't give them a higher reproductive chance and same for disadvantages and lower reproductive chance.

[yukoncpa]

I don't know if this will answer your natural selection question, but try here (http://www.straightdope.com/classics/a3_047.html)

[chrisnice]

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Right, I know we're still evolving but I was questioning whether there is natural selction. It just seems to me that any advantages that people may have don't give them a higher reproductive chance and same for disadvantages and lower reproductive chance.

[/ QUOTE ]

Natural selection doesnt play much of a role in the evolution of humans anymore. Technology and medicine is what keeps us strong today. 200 years ago nature made sure we were fit as a species, today we make ourselves fit.

[tolbiny]

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The principles behind natural selection still exist, so we are still "evolving"...it's just more likely that the social/technological effects are going to have more impact than natural selection. But yes, human society develops so much faster than evolutionary effects that I don't think they'll matter much.

[/ QUOTE ]

Whoever passes along their genes at a higher frequency to the next generation is, by definition, the most "fit". Natural selection still applies to our species- although it may be working on a slower/longer (whichever word youprefer) time frame than in the past. One of the key ideas that triggered darwin was that more offspring were being reproduced than could survive to produce their own prodigy. Because of medicine and technology a higher % of people are living to reproduce, but it is still a % and people still reproduce at different rates. Since this is true, and the sources of variation still exist then there is no reason to assume that natural selection has discontinued.

[Matt R.]

Yes, it's still going on. There will always be sexual selection unless something starts forcing randomized partnerships. People still die of diseases at a young age, thus lowering their fitness if they haven't reproduced yet. There's plenty of other disorders that greatly diminish someone's chance of reproductive success. The selective pressure is proportional to the genetic variance in a population. Until you get rid of all genetic variation, or somehow remove *all* selective pressures from an environment (i.e. through genetic engineering, perfect medicine, etc.), there will always be natural selection going on.

[PokerPadawan]

Brainstorm: There are cultural differences in rates of reproduction. For example, your typical white collar family has fewer babies than your typical blue collar one. You might consider this selection, but it isn't really, since it is mostly a life choice. And it would only have an effect on biological evolution if there is a genetic difference between those two populations. I think humans, though, are sufficiently genetically mixed that there probably isn't.

[PokerPadawan]

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The selective pressure is proportional to the genetic variance in a population. Until you get rid of all genetic variation, or somehow remove *all* selective pressures from an environment (i.e. through genetic engineering, perfect medicine, etc.), there will always be natural selection going on.

[/ QUOTE ]

You are forgetting that the Fundamental Theorem of Natural Selection is only applicable in restricted cases and doesn't necessarily hold in epistatic, recombinative, and other generally messy cases. Also, the genetic variance in the human population is probably much smaller than the phenotypic and environmental variance. I'm just guessing. I've never read a paper on this. But you can just look around and see that most causes of death are either common to us all (cancer, heart disease) or are environmental (accidents, starvation). Most selection based on mate preference and such are phenotypic (blond hair, symmetric face) or external (wealth, power).

[Rduke55]

There was just a thread on this a couple of weeks ago.
Most of the people commenting in this thread are wrong. Natural selection is still around. Gene flow due to migration, diseases, etc.
We're not going to get rid of it. Just because we haven't seen the huge differences (such as speciation) that we have seen in the past does not mean that it is not applicable. It's ridiculous to think that because we haven't changed in major ways over the past few thousand years that we've overcome natural selection. Evolution is typically very slow as we perceive it. A lot of animals have very long periods of apparent stagnation. Lampreys, crocodiles, and sharks look pretty similar now as they did in prehistoric times.
Would you say bowerbirds are free of natural selection? They have no natural predators and plenty of food. So much so that they spend most of the time constructing elaborate bowers to try and attract females (sexual selection).

[Rduke55]

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You are forgetting that the Fundamental Theorem of Natural Selection is only applicable in restricted cases and doesn't necessarily hold in epistatic, recombinative, and other generally messy cases.

[/ QUOTE ]

Why do you think this? Look at the literature on antibiotic resistance in bacteria. Lots of recombination and epistatic interactions there and it's definitely natual selection.

[ QUOTE ]
Also, the genetic variance in the human population is probably much smaller than the phenotypic and environmental variance.

[/ QUOTE ]

Source?

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I'm just guessing. I've never read a paper on this. But you can just look around and see that most causes of death are either common to us all (cancer, heart disease) or are environmental (accidents, starvation).

[/ QUOTE ]

But different populations have different incidences of diseases - in many cases due to genetics. It's ridiculous to make a statement like that in defense of your argument becaue I would use it to say the opposite.

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Most selection based on mate preference and such are phenotypic (blond hair, symmetric face) or external (wealth, power).

[/ QUOTE ]

I'm confused by this as well. Non-sexual selection is based on phenotypes too.

[PokerPadawan]

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Most of the people commenting in this thread are wrong.

[/ QUOTE ]

Everyone is saying that it is still around, but probably not the most important factor in human evolution anymore. Are you saying this is wrong?

[Rduke55]

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Most of the people commenting in this thread are wrong.

[/ QUOTE ]

Everyone is saying that it is still around, but probably not the most important factor in human evolution anymore. Are you saying this is wrong?

[/ QUOTE ]

I'm saying it varies between populations and times and you cannot make a statement like that based on the information people are putting foward.

[PokerPadawan]

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You are forgetting that the Fundamental Theorem of Natural Selection is only applicable in restricted cases and doesn't necessarily hold in epistatic, recombinative, and other generally messy cases.

[/ QUOTE ]

Why do you think this? Look at the literature on antibiotic resistance in bacteria. Lots of recombination and epistatic interactions there and it's definitely natual selection.

[/ QUOTE ]

You're statement makes it clear you didn't understand what I'm saying. Do you know what the Fund. Thm. of Nat. Sel. is? It is the statement that the rate of evolution is proportional to the genetic variance. I'm just saying it doesn't apply in most cases.

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Also, the genetic variance in the human population is probably much smaller than the phenotypic and environmental variance.

[/ QUOTE ]

Source?

[/ QUOTE ]

Read my next sentence: "I'm just guessing."

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I'm just guessing. I've never read a paper on this. But you can just look around and see that most causes of death are either common to us all (cancer, heart disease) or are environmental (accidents, starvation).

[/ QUOTE ]

But different populations have different incidences of diseases - in many cases due to genetics. It's ridiculous to make a statement like that in defense of your argument becaue I would use it to say the opposite.

[/ QUOTE ]

I'm not arguing that there is not a small effect due to natural selection. Why are you trying to back me into that corner? You need to reread more carefully. Read what we are all saying more carefully.

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Most selection based on mate preference and such are phenotypic (blond hair, symmetric face) or external (wealth, power).

[/ QUOTE ]

I'm confused by this as well. Non-sexual selection is based on phenotypes too.

[/ QUOTE ]

I was trying to distinguish natural from unnatural (man-made) selection processes. The OP was asking about natural selection. Phenotypic was the wrong word, but I don't know what word would mean unnatural pressure. External?

[Rduke55]

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You're statement makes it clear you didn't understand what I'm saying. Do you know what the Fund. Thm. of Nat. Sel. is? It is the statement that the rate of evolution is proportional to the genetic variance. I'm just saying it doesn't apply in most cases.

[/ QUOTE ]

If you're referring to Fisher's work then yes, I'm quite familiar with it. And that's not the way it was originally stated or the modern version of it. And your substitution of "evolution" instead of "fitness" is misleading.

You're making a very common mistake in interpreting it. Fisher's original work was misconstrued for decades as stating what you alluded to previously. In fact, the whole reason it is commonly misunderstood is because of Fisher's feud with Wright and Wright's misinterpretation of it as being the dogmatic statement you made. Just putting that statement out without looking at the papers or at least reviews is vastly oversimplifying the concept. For example, Fisher stated that average fitness of the group is only useful in a wider context (when compared to other groups and the environment) not as a stand-alone.

If you go read some more recent papers on it you'll see what I am saying.
In fact, Fisher's later work from the later 40's onward talks about junctions and recombinations and their influence on NS.

And even so, another major point is that with the older misinterpretation of Fisher's work, it still is true for a part of natural selection and you can't use a refutation of that aspect as evidence that humans are free of natural selection.

Sorry, I'm rambling.

[Rduke55]

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I'm not arguing that there is not a small effect due to natural selection.

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It's more than a small effect.

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You need to reread more carefully. Read what we are all saying more carefully.

[/ QUOTE ]

I did read the "I'm just guessing" part. /images/graemlins/tongue.gif
But seriously, there are some GIANT misconceptions in this thread (and the other ones on this topic).

[ QUOTE ]
I was trying to distinguish natural from unnatural (man-made) selection processes. The OP was asking about natural selection. Phenotypic was the wrong word, but I don't know what word would mean unnatural pressure. External?

[/ QUOTE ]

I may be misunderstanding you here but which traits are the ones specific to humans?
I'm assuming you don't consider hair color and facial symmetry man-made traits.
And many species use resources as a form of mate-selection so that's not specific to humans either.

[PokerPadawan]

This is interesting. I think we probably agree mostly on this. I haven't read recent reviews on the FTNS, but I do agree that it is a vast oversimplication. I would never use it to argue anything. And you're right that I did mean fitness instead of evolution. I bet to a biologist that is a stupid mistake, much like the confusing of mass and weight is to a physicist. I just see the FTNS thrown around and it bothers me, because I don't think it is as general as most people seem to think it is.

[PokerPadawan]

Human-specific selection? People in some countries get better health care. Some people choose to ride motorcycles. Some governments "encourage" boy babies. Would these work?

[Rduke55]

[ QUOTE ]
This is interesting. I think we probably agree mostly on this. I haven't read recent reviews on the FTNS, but I do agree that it is a vast oversimplication. I would never use it to argue anything. And you're right that I did mean fitness instead of evolution. I bet to a biologist that is a stupid mistake, much like the confusing of mass and weight is to a physicist. I just see the FTNS thrown around and it bothers me, because I don't think it is as general as most people seem to think it is.

[/ QUOTE ]

It certainly isn't and that's one of the big problems. As a strict mathematical theorem it definitely has some problems, which is the source of a lot of the antipathy people have for it. But the theorem indicates some concepts that are pretty deep in evolutionary thought.

[Rduke55]

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Human-specific selection? People in some countries get better health care. Some people choose to ride motorcycles. Some governments "encourage" boy babies. Would these work?

[/ QUOTE ]

In that most other species lack motorcycles, yes.
However it's dangerous to say stuff like bank accounts are an aspect of human-specific selection when there are analogous (homologoous) examples in nature.

[Rduke55]

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This is interesting. I think we probably agree mostly on this. I haven't read recent reviews on the FTNS, but I do agree that it is a vast oversimplication. I would never use it to argue anything. And you're right that I did mean fitness instead of evolution. I bet to a biologist that is a stupid mistake, much like the confusing of mass and weight is to a physicist. I just see the FTNS thrown around and it bothers me, because I don't think it is as general as most people seem to think it is.

[/ QUOTE ]

What is your field? I assumed you were a biologist-type.

[PokerPadawan]

I'm an astrophysicist and astrobiologist, but I've thought a lot about how evolution might proceed on other worlds.

[Go Blue]

But do "diseases" really act against natural selection? I'm not an expert in this field, so I could be wrong, but many diseases (I think) happen by chance. For example, you can consider Down Syndrome (sp?) an example, but that can happen to anyone's offspring. Same with cancer, as another example. What I was specifically thikning of was: what IS really needed in today's society (again, restricting this to just developed nations) to have a higher reproductive success? A long time ago, it may have been something like the ability to run faster, being physically fit, being able to think better, etc. But now, is anything like this really an evolutionary advantage still? For example, being smart can make you more money and get you a good woman. But if you're not smart, you can still make a living and mate with someone. Being more physically adaptive (e.g., stronger, faster) can make you more physically attractive and get you a good woman. But if you don't posses these characteristics, you can either be successfully via being smart, or just survive on some blue collar job; there will be SOMEONE out there to mate with. I think this is in a big part due to laws against polygamy. If polygamy was still allowed, there is a good chance that all the women would take the few men that are really good looking and built, or those with money, leaving everyone else out. Does this make sense?

[PokerPadawan]

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If polygamy was still allowed, there is a good chance that all the women would take the few men that are really good looking and built, or those with money, leaving everyone else out.

[/ QUOTE ]

Do you really think women would do that? Sounds more like a male fantasy. /images/graemlins/wink.gif

[purnell]

IMO it is trivially correct that as long as some people reproduce and others don't, natural selection is still taking place. This would still be the case even in the case of enforced universal eugenics.

"You cannot go against nature, because when you do
Goin' 'gainst nature is part of nature too."


/images/graemlins/smirk.gif

[purnell]

[ QUOTE ]
I don't know if this will answer your natural selection question, but try here (http://www.straightdope.com/classics/a3_047.html)

[/ QUOTE ]

/images/graemlins/laugh.gif Thanks for the belly laugh.

[Go Blue]

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If polygamy was still allowed, there is a good chance that all the women would take the few men that are really good looking and built, or those with money, leaving everyone else out.

[/ QUOTE ]

Do you really think women would do that? Sounds more like a male fantasy. /images/graemlins/wink.gif

[/ QUOTE ]

I think they'd have no other choice, just like back in the day. /images/graemlins/smirk.gif

[Rduke55]

[ QUOTE ]
But do "diseases" really act against natural selection? I'm not an expert in this field, so I could be wrong, but many diseases (I think) happen by chance. For example, you can consider Down Syndrome (sp?) an example, but that can happen to anyone's offspring. Same with cancer, as another example. What I was specifically thikning of was: what IS really needed in today's society (again, restricting this to just developed nations) to have a higher reproductive success? A long time ago, it may have been something like the ability to run faster, being physically fit, being able to think better, etc. But now, is anything like this really an evolutionary advantage still? For example, being smart can make you more money and get you a good woman. But if you're not smart, you can still make a living and mate with someone. Being more physically adaptive (e.g., stronger, faster) can make you more physically attractive and get you a good woman. But if you don't posses these characteristics, you can either be successfully via being smart, or just survive on some blue collar job; there will be SOMEONE out there to mate with. I think this is in a big part due to laws against polygamy. If polygamy was still allowed, there is a good chance that all the women would take the few men that are really good looking and built, or those with money, leaving everyone else out. Does this make sense?

[/ QUOTE ]

I'm a little confused by the beginning of your post ("work against natural selection").
Diseases are often "agents of selection." Look at malaria. Several groups of humans that live in tropical regions have resistance to malaria in some form. Whiteys don't. Therein lies on of the big problems say, Britain had, in colonizing certain areas.
These kinds of things happen a lot. The Native Americans were very susceptible to many of the diseases Europeans brought over. Europeans weren't as susceptible because they had evolved some resistance.
Even now it is postulated that the numeber of AIDS resistant people is increasing in certain areas of Africa because of the disease's prevalence there.
Diseases like cancer seem like they are going against this model but it's trickier than that. Because they most often occur after the animal's peak (or at least most active) stage of reproduction, selection does not have as much influence here. In fact, Alfred Wallace had an interesting manuscript on the adaptive qualities of senescence (presumably including cancer). There's also some recent work suggesting that the incidence of cancer in humans is due to certain trade-offs.

As to the second point in your post, it's not necessarily that you can mate but how many offspring you have, how many offspring they have, etc., etc.

[maurile]

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Natural selection doesnt play much of a role in the evolution of humans anymore. Technology and medicine is what keeps us strong today.

[/ QUOTE ]
Your statement implies that everyone tends to have the same number of children (or at least that any differences are not correlated with heritable traits), which is clearly false.

[Max Weinberg]

I read something a while ago that postulated that cultural evolution had taken the place of "natural" evolution with regards to how humans are evolving. It said that the reason why we went from stone hatchets to the atom bomb in a few million years was due more to our exponentially faster cultural growth, rather than genetic evolution.

So I suppose that even though we are breeding more weakness into the human species as a whole (since we can cure or assuage most ailments), our huge cultural/technological evolution more than makes up for it. Just compare present day technology with that of a hundred years ago and imagine what it will be in another hundred years. Faulty genes won't make much of a difference when we can go in and systematically repair them with nanobots and [censored].