/sci/ - Science & Math

>>10301212
Excerpt:
>Heritability Is Not Necessarily Constant
>Interestingly, heritabilities are not constant. For example, estimates of heritability for first lactation milk yield in dairy cattle nearly doubled from approximately 25% in the 1970s to roughly 40% in recent times. Heritability can change over time because the variance in genetic values can change, the variation due to environmental factors can change, or the correlation between genes and environment can change. Genetic variance can change if allele frequencies change (e.g., due to selection or inbreeding), if new variants come into the population (e.g., by migration or mutation), or if existing variants only contribute to genetic variance following a change in genetic background or the environment. The same trait measured over an individual's lifetime may have different genetic and environmental effects influencing it, such that the variances become a function of age. For example, variance in weight at birth is influenced by maternal uterine environment, and variance in weight at weaning depends on maternal milk production, but variance of mature adult weight is unlikely to be influenced by maternal factors, which themselves have both a genetic and environmental component. Heritabilities may be manipulated by changing the variance contributed by the environment. Empirical evidence for morphometric traits suggests lower heritabilities in poorer environments, but not for traits more closely related to fitness (Charmantier & Garant, 2005). Understanding how heritability changes with environmental stressors is important for understanding evolutionary forces in natural populations (Charmantier & Garant, 2005).

>>10301256
>*Heritability...

>>10297354
>>10297385
Excerpt:
>Heritability Is Not Necessarily Constant
>Interestingly, heritabilities are not constant. For example, estimates of heritability for first lactation milk yield in dairy cattle nearly doubled from approximately 25% in the 1970s to roughly 40% in recent times. Heritability can change over time because the variance in genetic values can change, the variation due to environmental factors can change, or the correlation between genes and environment can change. Genetic variance can change if allele frequencies change (e.g., due to selection or inbreeding), if new variants come into the population (e.g., by migration or mutation), or if existing variants only contribute to genetic variance following a change in genetic background or the environment. The same trait measured over an individual's lifetime may have different genetic and environmental effects influencing it, such that the variances become a function of age. For example, variance in weight at birth is influenced by maternal uterine environment, and variance in weight at weaning depends on maternal milk production, but variance of mature adult weight is unlikely to be influenced by maternal factors, which themselves have both a genetic and environmental component. Heritabilities may be manipulated by changing the variance contributed by the environment. Empirical evidence for morphometric traits suggests lower heritabilities in poorer environments, but not for traits more closely related to fitness (Charmantier & Garant, 2005). Understanding how heritability changes with environmental stressors is important for understanding evolutionary forces in natural populations (Charmantier & Garant, 2005).

>>10289136
>>10289122
As for what the textbook says:
>See picture.
But keep in mind that IQ is thought to have a large heritable component.
>The general figure for the heritability of IQ, according to an authoritative American Psychological Association report, is 0.45 for children, and rises to around 0.75 for late adolescents and adults.[77][78] Heritability measures in infancy are as low as 0.2, around 0.4 in middle childhood, and as high as 0.9 in adulthood.[79][80] One proposed explanation is that people with different genes tend to reinforce the effects of those genes, for example by seeking out different environments.[9][81]
But it certainly isn't as dramatic as Lynn's bullshit.