1. Biological Anthropology
Population Genetics
Biological Anthropology

2. Population A (potentially) interbreeding group of organisms
(usually) a subset of a species

3. “Populations” Differ

4. How Should We Describe Populations?
Monogenic Traits
Qualitative
Discontinuous graph
Polygenic Traits
Quantitative
Continuous graph

5. Use Polygenic Traits? Advantage: often easily observable
Disadvantage: can change over an individual’s life time
Poorly suited for population studies

6. Racism A social/cultural phenomenon
Attempts to distinguish between human populations on the basis of polygenic traits
Used to justify hierarchies within society
Is not based on scientifically valid criteria

7. Use Monogenic Traits! Disadvantage: not always easily observable
Advantage: do not change over an individual’s life time
Useful in the study of populations
Genetic Markers = monogenic traits in which the genotype is known

8. Genetic polymorphism
When two or more phenotypes exist within a population
that means that the population exhibits
variation
for that trait
and
variation
is what makes
evolution
possible

9. Adaptation a trait that increases an organism’s reproductive success
What adaptation is being measured here?
How might this adaptation increase an individual’s reproductive success?

10. Adaptation (a classic example)
The wing color of the Peppered Moth is a monogenic trait

11. Adaptation produced by natural selection in the context of a particular environment
A light variant mating with a dark variant
Light and dark variants on light and dark backgrounds

12. Smokestacks during the Industrial Revolution
Adaptation produced by natural selection in the context of a particular environment
Smokestacks during the Industrial Revolution

13. A change in allele frequency from one generation to another
Evolution defined
drum roll please…
A change in allele frequency from one generation to another

14. This means that… the unit of selection is the individual while
the unit of evolution is the population

15. Population Genetics
Studies how evolution occurs in populations of organisms
Population – a (geographically localized) group of individuals in a species that share a common gene pool and tend to find their mates within this group

16. (and establish a population)
Let’s run away!
(and establish a population)
Fabulous Baker Island

17. What are the factors that could influence the evolution of our population?
Founder’s effect
Natural selection
Mutation
Migration
Assortative mating
Positive
negative
Genetic drift

18. Founder’s effect
How well would we represent the population from which we are derived?
SoCal!

19. Natural Selection
Do blondes have more fun (and more early onset skin cancer)?
Is it better to be redder?
Hereditary diseases, anyone?
Other possibilities?

20. Mutation Random mutations Heightened mutation rates? Cosmic rays?
Uranium ore

21. Hypothesized migration pattern of the Pacific Islands
Do some people leave?
Do others arrive?
Did some “visit”?
Gene flow vs. migration
Hypothesized migration pattern of the Pacific Islands

22. Positive Assortative Mating Negative Assortative Mating
phenotypically similar organisms
increases homozygosity
decreases variation
phenotypically dissimilar organisms
increases heterozygosity
increases variation

23. the random factor, or “joker in the deck”
Genetic Drift
the random factor, or “joker in the deck”

24. A genetic bottleneck reduces a population temporarily to very low levels, removing much of its genetic diversity.

25. by Robert Dodd (artist & engraver); 2 Oct., 1790
Mutiny on the Bounty
by Robert Dodd (artist & engraver); 2 Oct., 1790

26. fled to Pitcairn Island
In 1790, 9 Bounty mutineers plus 18 Tahitians (six men, 11 women and a baby)
fled to Pitcairn Island

27. The Pitcairn Islanders today
app. 60 people
(the smallest democracy in the world!)