Stanford geneticist: Human intelligence is declining

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Re: Stanford geneticist: Human intelligence is declining

#21  Postby stevecook172001 » Nov 20, 2013 6:24 am

Veida wrote:It isn't clear to me that selection on brainpower is less today than it used to be. Seems to me that selection pressure might have been stronger on other things than brains before - things such as on endurance, strength, resistance to infection, etc, that are less important today. I wouldn't be surprised if selection on brains is actually stronger today than it used to be.

Natural selection occurs in the unforgiving crucible an organism's capacity to survive to reproductive age in the face of unrelenting environmental demands. Any organism that does not meet these demands will die before that point and so not pass on its genes to a next generation. It's as simple and as brutal as that. To that extent, since the very earliest formations of complex human civilisation itself, we have at least partially removed ourselves from that cold equation. However, as our technologies have further advanced, the process of removal has accelerated in recent centuries in many parts of the world. So, I am baffled as to why you think that natural selection pressures on human cognition will have increased over time. I think you may be confusing cultural selection pressures with genetic ones. Cultural selection pressures will drive learned cognition. They have absolutely no effect on the genetic contribution to cognition. Or, at least, they will have no effect if reproductive success is not directly implicated in those cultural pressure, which, in principle, it is possible for them to be I guess. However, if you think that is what has occurred, then it is incumbent on you to give at least one example because I, for one, am at a loss to think of one.
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Re: Stanford geneticist: Human intelligence is declining

#22  Postby tuco » Nov 25, 2013 8:15 am

James Flynn: Why our IQ levels are higher than our grandparents' - http://www.ted.com/talks/james_flynn_wh ... rents.html
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Re: Stanford geneticist: Human intelligence is declining

#23  Postby Beatsong » Nov 25, 2013 8:34 am

According to the doctor, humans were at their most intelligent when “every individual was exposed to nature’s raw selective mechanisms on a daily basis.” Under those conditions, adaption, he argued, was much more of a matter than fight or flight. Rather, says the scientists, it was a sink or swim situation for generations upon generations.


This is moronic. Individuals never have been exposed to nature's selective mechanisms, because selection does not act to change anything about the individual. It's only the species as a whole that is exposed to nature's selective mechanisms.

Furthermore, the species is so exposed now exactly as it always has been, and exactly the way that every species always has been and can't not be. It's just that the environment acting upon us has changed, as it too always does.

The idea that the proximity of natural peril makes people more intelligent should be easily testable (if you're one of those people who believe that intelligence itself is testable). Just compare the intelligence test results of people in societies where that peril is still a part of everyday life, with those of us pampered softies in the west.
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Re: Stanford geneticist: Human intelligence is declining

#24  Postby Veida » Nov 25, 2013 9:03 am

stevecook172001 wrote:Natural selection occurs in the unforgiving crucible an organism's capacity to survive to reproductive age in the face of unrelenting environmental demands. Any organism that does not meet these demands will die before that point and so not pass on its genes to a next generation. It's as simple and as brutal as that.

No, that's actually not a fair description of natural selection.

Natural selection is about differential reproductive success. Dying before reproductive age is one way to be worse than others at reproducing. Another way is to have less offspring. Natural selection can be in play even if no single individual dies before reproductive age, and even if all individuals have offspring. All that is required is that there is a difference in how well individuals reproduce, and that the traits which cause this are hereditary.

Therefore, as long as on average, those who are slightly better endowed in terms of intelligence have slightly more children than those who are slightly less fortunate, natural selection will favor higher intelligence.

It remains to be shown that this is not the case.
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Re: Stanford geneticist: Human intelligence is declining

#25  Postby Beatsong » Nov 25, 2013 9:17 am

Veida wrote:Therefore, as long as on average, those who are slightly better endowed in terms of intelligence have slightly more children than those who are slightly less fortunate, natural selection will favor higher intelligence.


... assuming (as does the opposite POV that you are disputing) that intelligence is a genetic endowment. :whistle:
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Re: Stanford geneticist: Human intelligence is declining

#26  Postby Veida » Nov 25, 2013 9:25 am

Beatsong wrote:
Veida wrote:Therefore, as long as on average, those who are slightly better endowed in terms of intelligence have slightly more children than those who are slightly less fortunate, natural selection will favor higher intelligence.


... assuming (as does the opposite POV that you are disputing) that intelligence is a genetic endowment. :whistle:

Or at least that genetic factors contribute to that which we call intelligence.
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Re: Stanford geneticist: Human intelligence is declining

#27  Postby Veida » Nov 25, 2013 9:52 am

Veida wrote:Or at least that genetic factors contribute to that which we call intelligence.

It seems to me that there must be such factors. I don't see any other way that our large brains could have developed. They make birth difficult, they make childhood last a long time, they require an anatomy that interferes with female walking and running, and they require lots of energy. Therefore, they must provide substantial benefits, and moreover, there must be genetic factors that can be selected for. It's unreasonable to think that we got our brains by genetic drift.
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Re: Stanford geneticist: Human intelligence is declining

#28  Postby Beatsong » Nov 25, 2013 10:21 am

Sure. Our brains, like any other part of us, are the result of how we have evolved within the context of natural selection. But that doesn't mean that there are significant genetic differences between most individuals now in the structure of those brains.

The anatomy of our hands and feet is also evolved, but (barring specific and extremely rare deformities) everyone is born with the same number of fingers and toes.
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Re: Stanford geneticist: Human intelligence is declining

#29  Postby Veida » Nov 25, 2013 10:58 am

Right, and everyone is born with the same number of brains.

ETA: I don't see your point. There is obviously variation in hands, and there is obviously variation in brains.
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Re: Stanford geneticist: Human intelligence is declining

#30  Postby Agrippina » Nov 25, 2013 1:35 pm

Yes, mostly, everyone is born with one brain (made up of difference parts). I don't think we could function with more than one brain.
A mind without instruction can no more bear fruit than can a field, however fertile, without cultivation. - Marcus Tullius Cicero (106 BCE - 43 BCE)
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Re: Stanford geneticist: Human intelligence is declining

#31  Postby Veida » Nov 25, 2013 1:57 pm

Agrippina wrote: I don't think we could function with more than one brain.

Evidence says otherwise :-)

The Hensel twins - one body, two heads: http://www.bbc.co.uk/news/magazine-22181528
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Re: Stanford geneticist: Human intelligence is declining

#32  Postby Beatsong » Nov 25, 2013 2:13 pm

Veida wrote:There is obviously variation in hands, and there is obviously variation in brains.


Well yeah, there's variation in everything. The problem comes when we try to extrapolate specific things like a singular scale of "intelligence" from such variation. The simple and trivial fact that variation exists, does not mean that we can assume whatever we like about how that variation manifests itself.
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Re: Stanford geneticist: Human intelligence is declining

#33  Postby Agrippina » Nov 25, 2013 3:26 pm

Veida wrote:
Agrippina wrote: I don't think we could function with more than one brain.

Evidence says otherwise :-)

The Hensel twins - one body, two heads: http://www.bbc.co.uk/news/magazine-22181528


Two heads, two people. You called them "twins."
A mind without instruction can no more bear fruit than can a field, however fertile, without cultivation. - Marcus Tullius Cicero (106 BCE - 43 BCE)
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Re: Stanford geneticist: Human intelligence is declining

#34  Postby Veida » Nov 25, 2013 3:38 pm

Beatsong wrote:
Veida wrote:There is obviously variation in hands, and there is obviously variation in brains.


Well yeah, there's variation in everything. The problem comes when we try to extrapolate specific things like a singular scale of "intelligence" from such variation. The simple and trivial fact that variation exists, does not mean that we can assume whatever we like about how that variation manifests itself.

Did I, though?

What I was arguing against was the notion that because virtually nobody dies before reproductive age anymore, at least not in the western world, natural selection does not provide any pressure towards maintaining or increasing human intelligence (whatever that is).

The only assumption made (and that is shared by the opposing view) is that whatever it is we call intelligence is to some extent heritable. I haven't claimed, for example, that intelligence can be measured as a single value.
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Re: Stanford geneticist: Human intelligence is declining

#35  Postby Veida » Nov 25, 2013 3:44 pm

Agrippina wrote:
Veida wrote:
Agrippina wrote: I don't think we could function with more than one brain.

Evidence says otherwise :-)

The Hensel twins - one body, two heads: http://www.bbc.co.uk/news/magazine-22181528


Two heads, two people. You called them "twins."


My objection wasn't entirely serious - and I don't wish to go off-topic - so I won't go there.
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Re: Stanford geneticist: Human intelligence is declining

#36  Postby Beatsong » Nov 25, 2013 3:44 pm

OK. Fair enough. :thumbup:
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Re: Stanford geneticist: Human intelligence is declining

#37  Postby CAPSLOCK » Jun 07, 2014 9:03 pm

Hi,

Firstly, this is my first post, and while I do not intend to simply re-hash a old topic; I think there is a fairly important aspect to this conversation which has been overlooked.

Barring whether or not Crabtree's findings are accurate, verifiable, falsifiable and repeatable, it raises the question as to whether or not increased intelligence is still evolutionary favourable. Evolution acts to select the "fittest", the members of a species which have genetic adaptions that provide a advantage in their environment.

If studies found a tendency for a species-wide decrease in IQ, this doesn't mean that the advent modern medicine and society is preventing evolution, only that the environment has changed and there is no longer selective pressure for increasing intelligence.

Just my thoughts, I would highly appreciate any feedback. This really isn't my area of expertise, just something that interests me.
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Re: Stanford geneticist: Human intelligence is declining

#38  Postby Darwinsbulldog » Jun 08, 2014 5:56 am

CAPSLOCK wrote:Hi,

Firstly, this is my first post, and while I do not intend to simply re-hash a old topic; I think there is a fairly important aspect to this conversation which has been overlooked.

Barring whether or not Crabtree's findings are accurate, verifiable, falsifiable and repeatable, it raises the question as to whether or not increased intelligence is still evolutionary favourable. Evolution acts to select the "fittest", the members of a species which have genetic adaptions that provide a advantage in their environment.

If studies found a tendency for a species-wide decrease in IQ, this doesn't mean that the advent modern medicine and society is preventing evolution, only that the environment has changed and there is no longer selective pressure for increasing intelligence.

Just my thoughts, I would highly appreciate any feedback. This really isn't my area of expertise, just something that interests me.


Intelligence will be regulated by evolution on a benefits vs costs basis. In terms of gross size, the human brain can't get much bigger, so improvements would have to be made on the connections. Of course, caesarian ops are a way to get around birth canal constraints.

Given the cost of social welfare, the negative aspects of globalization, the increase of robotics, etc, etc, intelligence may once more become vital for human survival. The poor, the uneducated and the lees bright may be in for a really, really rough time. Of course this has been true in less developed nations for some time, but now I think it will be global.
Most people [if the mass media are to be believed] are habituated to think that a global corporation can announce record billions of dollars in profit AND sacking thousands of workers in the same press release. Elections are now about the strength of the economy, with issues like education, welfare, equity etc pushed into the background.
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"When an animal carries a “branch” around as a defensive weapon, that branch is under natural selection".
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Re: Stanford geneticist: Human intelligence is declining

#39  Postby Arcanyn » Jun 08, 2014 6:34 am

I think there's still quite a bit of selection for intelligence - just look how pervasive "alternative" medicine is. All the time, people lacking in critical thinking skills are choosing to forgo real medical treatment in favour of crystals or homeopathy or voodoo dolls or whatever, and dying of what are often easily treatable conditions. Whereas those with critical thinking skills will choose real medicine, and be much more likely to survive.
Never ascribe to stupidity that which is the logical consequence of malice.
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Re: Stanford geneticist: Human intelligence is declining

#40  Postby Cito di Pense » Jun 08, 2014 7:43 am

Arcanyn wrote:Whereas those with critical thinking skills will choose real medicine, and be much more likely to survive.


Critical thinking skills are trained, not inherited. Native intelligence is something else again, and there's simply no way to measure changes in it, because we keep changing the tests to meet society's felt needs. Wake me up when there's a scientific idea in this thread. Otherwise, you're all just being trolled by Fifth Ape. Elvis has exited the arena.

I don't mean to pick on you, specifically, Arcanyn, you're just the most recent post. Your comment, sadly, is only an opinion, and it's demonstrably wrong. More intelligent people may be more or less educable than average, depending on your educational models and paradigms. Educational psychology produces fads demanded of it by society.

Scads of people with ordinary (average) intelligence are enamoured of homeopathy. It's isn't just the stupid ones. Anyone who resents the authority of the medical establishment (or of science in general) might thumb his nose at it for reasons having nothing to do with intelligence, unless you define intelligence tautologically, as you've implied you've done, above.
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Translation by Elbert Hubbard: Do not take life too seriously. You're not going to get out of it alive.
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