Heritability estimates the source of differences among people. (genetic or environmental)

 Heredity : how the trait is obtained  Heritability: HOW MUCH of the variation within GROUPS is due to genetics.  DOES NOT REFLECT EXTENT TO WHICH TRAITS ARE PASSED DOWN FROM PARENT TO OFFSPRING  HERITABILITY ESTIMATES ONLY REFLECT WHAT CAUSES THE VARIATION IN THE TRAITS; THEY SAY NOTHING ABOUT WHAT CAUSES THE TRAITS THEMSELVES  Range from 0-1 (0%-100%)  If difference in population is due to genetic factors; heritability = 1 (100%)  If difference is due to environmental factors; heritability = 0. (0% due to genetics) Heritability increases when genetics are contributing more to the variation

 For instance, some humans in a population are taller than others; heritability attempts to identify how much genetics play a role in part of the population being taller. This does not mean that all people’s heights are determined 90% by genetics & 10% by environment  If difference in population in height is due to genetic factors then heritability = 1 (100%)  If difference in population in height is due to environmental factors then heritability = 0. (0% due to genetics)

1. If a person has a disorder with a heritability of 1, then the person will suffer from the disorder.  PKU is a disorder with a heritability of 1 (difference in variation of having disorder or not is due to genetics)  PKU can result in mental retardation, yet the retardation can be prevented if phenylalanine is removed from the person’s diet at birth, & if they watch their diet very carefully.  Therefore the disease can be prevented making the statement false. Something that is highly heritable does not have to present itself in the population.

2. The heritability of having fingers on each hand is 1.  The heritability of having five fingers on each hand is low; close to 1.  The source of variation here is usually environmental caused early on due to teratogens, and for adults, due to accidents.  The variation is not due to genetics.

3. Heritability and inherited are nearly opposite in meaning. Autism is inherited as is epilepsy, breast and colon cancer. Autism has a heritability of 90% Epilepsy 88% Breast Cancer 50% Colon Cancer 13% As environmental factors matter more to the manifestation of the disease, heritability goes down Heritability estimates tell us nothing about how genetic & environmental factors affect presence of traits

4. In mid 1950s America, the heritability for wearing earrings was very high.  Things that seem very noninheritable may have high heritability.  Fifty years ago when virtually only women wore earrings, the heritability of wearing earrings was very high. Certain genes were usually found in earring wearers that were not found in non-earring wearers.  Correlational data. The gene whose presence is correlated with wearing earrings need not play any direct role in causing that behavior.

 Identical twins do not have a heritability of 1, they have heritability of 0, since any variation is due to environment.

 As the environment gets more similar for individuals of very different heritabilities, heritability increases.  As the environment gets more similar, the environment becomes less a source of variation.

 The heritability of a group of individuals with relatively similar heredities in very different environments is relatively low.  As the heredities become more similar, genetics becomes less a source of variation.

If something has 100% heritability the environment still matters Heritability BETWEEN groups = 0 Heritability WITHIN groups = 1