3 ms·

The best simple explanations I've heard for the Flynn effect are better nutrition and outbreeding. The world today is seeing a historically unprecedented degree

by api 12y ago

The best simple explanations I've heard for the Flynn effect are better nutrition and outbreeding. The world today is seeing a historically unprecedented degree of migration and genetic mixing, which typically produces stronger not weaker offspring in various ways (on average). It's one way the Nazis were utterly wrong. Their program of Aryan purity would likely have produced a master race of inbred knuckle-dragging ubermenschen.

danielweber 12y ago
Once you exclude the nasty effects of inbreeding, what's the evidence that mixing leads to healthier offspring?
- api 12y ago
  It's actually a very complex subject. Start with things like outbreeding, heterozygote dominance, etc. https://en.wikipedia.org/wiki/Outcrossing https://en.wikipedia.org/wiki/Outcrossing https://en.wikipedia.org/wiki/Inbreeding_depression https://en.wikipedia.org/wiki/Inbreeding_depression https://en.wikipedia.org/wiki/Heterosis https://en.wikipedia.org/wiki/Heterosis There are of course counter-cases. Nothing in biology is totalistic or absolute, including this sentence. :) https://en.wikipedia.org/wiki/Outbreeding_depression https://en.wikipedia.org/wiki/Outbreeding_depression Yet most of the evidence I've seen e.g. in immunology (which doesn't suffer from the PC bias against studying it like IQ) suggests that on average outbreeding tends to boost fitness to some extent. More distant crosses tend to have healthier immune systems... again on average. To a great extent outbreeding is the entire point of sexual reproduction-- to use mating assortment to decrease the likelihood of being stuck with lower-fitness genes that keep repeating in the same lineage. If it didn't work that way we'd probably all reproduce by budding. Edit: wacko left-field hypothesis: what if the immune system boosting effects of outbreeding have helped the human race avoid a global super-plague brought on by unprecedented degrees of mobility? In other words-- what if the genetic effects of all that mobility have counter-balanced the immunological risks?
- aswanson 12y ago
  That's kind of like asking what's the evidence that smoking leads to cancer. Genetics works probabalistically; the chance that a deleterious mutation gets expressed increases for each generation of closed breeders.
tokenadult 12y ago
[Refers to submitted article before posting comment:] A) As for genetic factors related to the Flynn effect, I think the weight of the evidence is against reduction of inbreeding ("heterosis") having a large enough effect size to have much to do with explaining the Flynn effect. Flynn thinks so too, and shows his work.[1] I was actually somewhat influenced by the idea of "hybrid vigor" when I chose my wife, who has different continental ancestry from mine and indeed has blessed me with four children who are smart (by test,[2] not just by my opinion) and who appear to have good immune systems. This is part of tradition that goes back generations in my family of the men marrying women of a different "nationality." B) As for nutritional factors related to the Flynn effect, they have often been proposed, but hardly demonstrated at all. Evidence from a variety of sources, for example the famine that afflicted part but not all of the Netherlands during the German occupation near the end of World War II, and other more extensive data sets, suggest that nutrition too doesn't have enough effect size to explain more than a tiny part of the IQ score increases that make up the Flynn effect.[3] [1] http://www.psychometrics.cam.ac.uk/about-us/directory/beyond-the-flynn-effect#section-9 http://www.psychometrics.cam.ac.uk/about-us/directory/beyond... [2] http://www.davidsongifted.org/youngscholars/Article/Davidson_Young_Scholars___Qualification_Criteria_384.aspx http://www.davidsongifted.org/youngscholars/Article/Davidson... http://cty.jhu.edu/set/ http://cty.jhu.edu/set/ [3] http://www.sciencedirect.com/science/article/pii/S1570677X09000057 http://www.sciencedirect.com/science/article/pii/S1570677X09...
theorique 12y ago
Additionally, excluding and marginalizing the measured high-IQ (+1 sigma) population of Ashkenazi Jews probably handicapped the Third Reich. For which we should probably be thankful. Additionally, some of the top tier of those driven out of Europe contributed to US war projects (including the Manhattan Project), so the effect not only handicapped Nazi Germany but assisted the Allies.
IndianAstronaut 12y ago
This may have to do with the parasite and disease burden people in developing countries have. http://www.economist.com/node/16479286 http://www.economist.com/node/16479286

by api 12y ago

danielweber 12y ago

Once you exclude the nasty effects of inbreeding, what's the evidence that mixing leads to healthier offspring?

api 12y ago
It's actually a very complex subject. Start with things like outbreeding, heterozygote dominance, etc. https://en.wikipedia.org/wiki/Outcrossing https://en.wikipedia.org/wiki/Outcrossing https://en.wikipedia.org/wiki/Inbreeding_depression https://en.wikipedia.org/wiki/Inbreeding_depression https://en.wikipedia.org/wiki/Heterosis https://en.wikipedia.org/wiki/Heterosis There are of course counter-cases. Nothing in biology is totalistic or absolute, including this sentence. :) https://en.wikipedia.org/wiki/Outbreeding_depression https://en.wikipedia.org/wiki/Outbreeding_depression Yet most of the evidence I've seen e.g. in immunology (which doesn't suffer from the PC bias against studying it like IQ) suggests that on average outbreeding tends to boost fitness to some extent. More distant crosses tend to have healthier immune systems... again on average. To a great extent outbreeding is the entire point of sexual reproduction-- to use mating assortment to decrease the likelihood of being stuck with lower-fitness genes that keep repeating in the same lineage. If it didn't work that way we'd probably all reproduce by budding. Edit: wacko left-field hypothesis: what if the immune system boosting effects of outbreeding have helped the human race avoid a global super-plague brought on by unprecedented degrees of mobility? In other words-- what if the genetic effects of all that mobility have counter-balanced the immunological risks?
aswanson 12y ago
That's kind of like asking what's the evidence that smoking leads to cancer. Genetics works probabalistically; the chance that a deleterious mutation gets expressed increases for each generation of closed breeders.

tokenadult 12y ago

[Refers to submitted article before posting comment:] A) As for genetic factors related to the Flynn effect, I think the weight of the evidence is against reduction of inbreeding ("heterosis") having a large enough effect size to have much to do with explaining the Flynn effect. Flynn thinks so too, and shows his work.[1] I was actually somewhat influenced by the idea of "hybrid vigor" when I chose my wife, who has different continental ancestry from mine and indeed has blessed me with four children who are smart (by test,[2] not just by my opinion) and who appear to have good immune systems. This is part of tradition that goes back generations in my family of the men marrying women of a different "nationality." B) As for nutritional factors related to the Flynn effect, they have often been proposed, but hardly demonstrated at all. Evidence from a variety of sources, for example the famine that afflicted part but not all of the Netherlands during the German occupation near the end of World War II, and other more extensive data sets, suggest that nutrition too doesn't have enough effect size to explain more than a tiny part of the IQ score increases that make up the Flynn effect.[3] [1] http://www.psychometrics.cam.ac.uk/about-us/directory/beyond-the-flynn-effect#section-9 http://www.psychometrics.cam.ac.uk/about-us/directory/beyond... [2] http://www.davidsongifted.org/youngscholars/Article/Davidson_Young_Scholars___Qualification_Criteria_384.aspx http://www.davidsongifted.org/youngscholars/Article/Davidson... http://cty.jhu.edu/set/ http://cty.jhu.edu/set/ [3] http://www.sciencedirect.com/science/article/pii/S1570677X09000057 http://www.sciencedirect.com/science/article/pii/S1570677X09...

theorique 12y ago

Additionally, excluding and marginalizing the measured high-IQ (+1 sigma) population of Ashkenazi Jews probably handicapped the Third Reich. For which we should probably be thankful. Additionally, some of the top tier of those driven out of Europe contributed to US war projects (including the Manhattan Project), so the effect not only handicapped Nazi Germany but assisted the Allies.

IndianAstronaut 12y ago

This may have to do with the parasite and disease burden people in developing countries have. http://www.economist.com/node/16479286 http://www.economist.com/node/16479286