Download heritability estimates only reflect what causes the variation in the

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%)
Heritability increases when
genetics are contributing
more to the variation

If difference is due to environmental factors; heritability =
0. (0% due to genetics)
HERITABILITY OF HEIGHT IS 90%

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. FALSE :
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

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.
of having disorder or not is due to genetics)

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. FALSE
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. TRUE
Heritability estimates tell
us nothing about how
genetic & environmental
factors affect presence of
traits
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
4. TRUE

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.
5. FALSE

Identical twins do not have a heritability of 1,
they have heritability of 0, since any variation is
due to environment.
6. TRUE

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.
7. TRUE

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.
Heritability
WITHIN
groups = 1
Heritability
BETWEEN
groups = 0
If something has 100% heritability
the environment still matters