Genes and destruction

blackmonkeystatue said:
The average IQ has increased by 3 points a decade though in developed nations.
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Yeah so this is confusing me.

How do genes pass on increased intelligence? I can see that a different combo of genes can lower intelligence (down syndrome), but can't see how a mother and father can produce a combo that will allow increased intelligence of offspring.

Intelligence comes from genes and environment, but whatever you learn from the environment can't be passed onto your children, so what am i missing?
 
Down syndrome is usually due to problems with chromosome arrangement during meiosis. It is therefore not a good example of passing on 'stupid' genes.

There is genetic varation in the population that helps to determine intelligence potential. A combination of 2 parents can either lead to better potential or worse potential. There is basically no difference between the two situations.
 
bizzaroSquirrel,
You can pretty easily find agreement that the average IQ has increased by 3 points a decade though in developed nations. What you cannot easily find is an agreement about why.

Given that, what I'm about to say is purely speculation. Let's work with what you wrote though.

bizzaroSquirrel said:
I can see that a different combo of genes can lower intelligence (down syndrome), but can't see how a mother and father can produce a combo that will allow increased intelligence of offspring.
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Ok. So, if there were less of those "bad" combos, wouldn't it then follow that the average IQ would increase, since there are less of the negative interactions occurring to lower it? Think of it as subtracting a negative, you get positive results. These bad things only happen when the bad recessive genes line up. These bad recessive genes can only line up if they are present in both parents. The more distantly related the parents are, the less likely that both parents will have the same bad recessive genes because they have completely different blood lines.

bizzaroSquirrel said:
Intelligence comes from genes and environment, but whatever you learn from the environment can't be passed onto your children, so what am i missing?
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Well, technically it can. That's what evolution is. That doesn't really matter though.

Dealing with heritability and IQ and parents and kids etc, IQ has a correlation of .5. Let’s say that one parent has an IQ of 130 and the other has an IQ of 150. Average IQ is 100. These parents are 30 and 50 points about the IQ average IQ. The average is 40 [(30+50)/2]. IQ has a correlation of .5. (.5x40)=20. So the child would be expected to have an IQ of around 120. That is how intelligence is passed on. Maybe it isn't that people are actually becoming more intelligent, maybe it is just that we're realizing our true potential. An actual increase in the genes or something would require some evolutional step, and we haven't been tracking this stuff for very long. I wouldn't expect such things in a couple hundred years. I think we're just working with what we have, with what we have had all along.

About what you were saying though. The way I learned it is that everyone is born with a set IQ that cannot be increased, but can be lowered (i.e. brain damage). Remember IQ is just a way of measuring mental ability. I'm not sure of the exact distinctions, but as a child, children’s' abilities are more influenced by their environment. These environmental affects becomes less and less as they get older. By adulthood, their natural born IQ accounts for about 80% of their "intelligence". Certain skills can and do skew intelligence tests, but we do the best we can.

If you're interested in this have a look at http://psycprints.ecs.soton.ac.uk/archive/00000658/

It's long, but the best book I've found on the issue.
 
Well, actually. I'm not sure if I wrote the cousin example in this thread or the other, but it's a simple example. When first cousins mate (1st cousins share 1/8th the genes, .125 kinship correlation) their offspring will generally have an IQ of about 7 points less than it would normally. If less of that is happening, and the parents are more distantly related, then the average IQ would not be taking so many negative "hits" so to speak. Making it appear that it is going up, when actually, it is just not being negated so much. The -7 IQ points is true, but it is just an example. I don't think that many first cousins actually mate, but if you extrapolate you get the idea.
 
Spurious is right about Down syndrome, but I know what you meant Squirrel. I haven't read anything saying that Down syndrome has anything to do with heritability as much as that the risk increases with the mother's age. It is a result of an extra 21st chromosome.

Edit: Just did a search. Haven't found anything that says Down syndrome might be heritable. I found that there is a small risk with further pregnancies, but that may just tie into the fact that the general risk increases with age. Occurances seem to be sporadic.
 
blackmonkeystatue said:
Not really. When two individuals from increasingly different backgrounds/regions/whatever mate, there is less of a chance that the recessive genes will line up and cause problems because the more different they are, the more likely that they will have different genes and completely different histories/blood lines. The strong genes do not really seperate from the weak. Both are present, but the more diversity you have, the less chance you'll have of recessive problem genes to both be present and, well, cause problems. You don't really get rid of them, but you can do your best to cover them up.

First cousins share 1/8 of the same genes (genetic kinship correlation of .125). When first cousins procreate, the offspring will have an average IQ decrease of about 7 points. This is a result of the lack of diversity. This bad things result from inbreeding, there is an increasing chance that the recessive genes will line up. It would follow that the more diverse the gene selection, the less chance this has to occur.
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Inbreeding is separate from breeding within a population.

Recessive gene problems do not occur in healthy populations.

Mixing, while it may introduce "new" genes, also destroys, and your reply did not address that.
 
android said:
Inbreeding is separate from breeding within a population.
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I didn't mean inbreeding in terms of incest. I meant it in terms of the same group of people. Take the Amish, or the population of a rural somewhat isolated town with very few coming in or leaving. I meant it in terms of the opposite of:
out•breed•ing ( P ) Pronunciation Key (outbrdng)
n.
The breeding of distantly related or unrelated individuals, often producing a hybrid of superior quality.
Anthropology. The mating of persons from different groups, often as a consequence of proscriptions against marriage within the group.
From www.dictionary.com

Maybe I chose the wrong word, but you get the idea. It was not meant to be taken literally because I seriously doubt that many 1st cousins actually procreate. Infer the idea. It is an extreme case of poor genetic variation. Of course, the more varied, the less these things will occur.

android said:
Recessive gene problems do not occur in healthy populations.
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Well if that's true, then there is no such thing as a healthy human population on this earth.

android said:
Mixing, while it may introduce "new" genes, also destroys, and your reply did not address that.
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I think we need a definition of what you mean by "destroys". I do not consider a stronger population a result of destruction. If you mean that they will no longer be "pure", than you may have a point. There isn't really anyone that that is "pure" by any stretch of the imagination. The closest you’ll get to pure is some isolated tribe in Africa or South America in which even signs of genetic drift would be apparent. You’re thousands of years late if you’re looking for “pure”.

Edit: Please define what you mean by "destroys". If you mean what I think you mean, then I suppose you're not a fan of evolution to a certain extent. The human race should not have changed from its previous state, nor should it change ever. You apply that silly idea back far enough and we'd all still be in Africa.
 
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I fin dit so funny when people try and use science to confirm their distorted views.
 
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