Where does the Watson confusion come from?
• Confusing two separate questions:
1. What’s the universal, evolved architecture that we all share by
virtue of being humans?
2. Given a large population of people, to what extent can differences
between these people be accounted for by differences in their genes? (Questions
the source of variation)
▪ Heritability statistic - is only about differences (about
variance in a population)
▪ Heritability = Vgenes / ( Vgenes + Venvironment - Vg-e)
▪ Imagine if five pairs of identical twins are reared apart. The
were originally born in a hunter gatherer group in Botswana. Suppose we
kidnap one of each of the kids and raise them in California. People from
Botswana aren’t near sighted. We’re testing their eye sight. Some
genotypes will autocorrect and cause near-sightedness in the Californias,
while other genotypes buffer against this. SO even though they have the
same genotype, their
• Heritability of a trait always relative to a particular populationAND a
◦ IT TELLS YOU NOTHINGABOUT HOW EASY OR
DIFFICULT IT IS TO CHANGEATRAIT
◦ Heritability (h) was different in Botswana and CA even though they
had identical sets of genotypes
◦ h of eyesight was high in CA. Does this mean eyesight isn’t
changeable? NO - think of glasses, laser surgery, etc. To change, we need to know
optics and how the eye works: the structure of the mechanism (NOT the
heritability. Heritability is irrelevant)
• Number of legs are inherited. There is a difference in number of legs
(due to car accidents, etc.), BUT the number of variation DUE TO DIFFERENCES
IN THEIR GENES is very low.
◦ Similarly, the heritability in having a heart is ZERO, because
there is no genetic coding for not having a heart. However, there are aspects
of your heart that can have variability such as the color of your heart because
nature doesn’t really get affected by the color of your heart.
◦ ANOTHER EXAMPLE: there is low/no heritability for having
a stomach, but there is high heritability for the acidity of your stomach or the
shape of your stomach because nature doesn’t care.
• Heritability doesn’t apply