A review of polygenic inheritance

Global Patterns of Human Variation

• Can be examined genetically• Can be examined phenotypically• Are phenotypic differences concordant with genetic

differences?

Eight classes of geneticsimilarityenzyme & blood group loci

Arrayed by increasingdifference

Distribution of eight classesof skin pigmentationintensity

Concordance ordiscordance?

• However, there IS geographic structuring of allele frequencies. • Genetic distance map• 42 native human populations• Frequencies of 120 different alleles• Closer proximity in graph = greater genetic similarity• Related to geographic distances among the groups.

• PPPPPopu Populationdifferences

Average genetic differencesDistance curtails gene flow among groups

• Populational differences among human groups• Today, human races are distinguished by ethnic differences –

NOT by biological differences.– Differences in culture

• nationality• language• religion

– Biologically, there is no Jewish race, no African race, no African-American race, etc.

– But, biological differences may still be emphasized, even in sociology; e.g., people of color.

Effects of gene flow on populationse.g., microevolution in Ireland

• Data set: anthropometric (skull) measurements• Collected in 1930s• >7000 men from 30 of 31 counties • Phenotypic measurements converted into similarity

measurements: genetic distances• Plot of distances between samples from 30 counties.• Graphical pattern reveals the pattern of variation.

• Prediction: because of location, the four centrally located counties should be genetically similar to all of the other counties

• In a central position re of past migration routes and gene flow

H1: resulted from gene flow from Danish andNorwegian Viking invaders. One incursionInto; central Ireland involved 12,000 men.

M counties displaced away from the othercounties

Testing the hypothesis