For traits like height or IQ, individuals in a population vary. Heritability is a measure of how much of that variation is due to genes rather than environment. The higher the heritability of a trait, the more your phenotype is "determined" by genes.
Suppose your parents both have IQs of 130, which is 30 points above…
For traits like height or IQ, individuals in a population vary. Heritability is a measure of how much of that variation is due to genes rather than environment. The higher the heritability of a trait, the more your phenotype is "determined" by genes.
Suppose your parents both have IQs of 130, which is 30 points above their population mean of 100. If IQ is 100% heritable, that means both your parents have genes for 130 IQ. You inherit those genes, so your expected IQ is 130. Suppose IQ is 0% heritable. Now it doesn't matter who your parents are--your expected IQ is the population mean (100). Suppose IQ is 50% heritable. Then your expected IQ is in between your parents and the population mean (115).
Nigerian mean IQ is probably around 80. The 90th percentile is around 100. If two Nigerians with IQs of 100 have children, assuming 50% heritability, their children will (on average) have an IQ of 90. (The heritability of IQ is actually higher than 50%, but that's how the numbers work in the example.)
(2) There are many crackpots in the hereditarian camp, and it's hard to know who to listen to. I mention Aporia. Also people like Razib Khan, Gregory Cochran, Crémieux, i/o, Steve Sailer, Charles Murray, Neven Sesardić...
(1) The answer is (b).
For traits like height or IQ, individuals in a population vary. Heritability is a measure of how much of that variation is due to genes rather than environment. The higher the heritability of a trait, the more your phenotype is "determined" by genes.
Suppose your parents both have IQs of 130, which is 30 points above their population mean of 100. If IQ is 100% heritable, that means both your parents have genes for 130 IQ. You inherit those genes, so your expected IQ is 130. Suppose IQ is 0% heritable. Now it doesn't matter who your parents are--your expected IQ is the population mean (100). Suppose IQ is 50% heritable. Then your expected IQ is in between your parents and the population mean (115).
Nigerian mean IQ is probably around 80. The 90th percentile is around 100. If two Nigerians with IQs of 100 have children, assuming 50% heritability, their children will (on average) have an IQ of 90. (The heritability of IQ is actually higher than 50%, but that's how the numbers work in the example.)
For more explanation see: https://www.edge.org/response-detail/27199
(2) There are many crackpots in the hereditarian camp, and it's hard to know who to listen to. I mention Aporia. Also people like Razib Khan, Gregory Cochran, Crémieux, i/o, Steve Sailer, Charles Murray, Neven Sesardić...