Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Koinophilia wikipedia , lookup
Polymorphism (biology) wikipedia , lookup
Neuronal ceroid lipofuscinosis wikipedia , lookup
Dominance (genetics) wikipedia , lookup
Genetic drift wikipedia , lookup
Genetic studies on Jews wikipedia , lookup
Population genetics wikipedia , lookup
Public health genomics wikipedia , lookup
Tay–Sachs disease wikipedia , lookup
Ashkenazi Jews & Intelligence Freud, Einstein, Mahler Kristy Brady 8 February 2006 Outline • • • • Heterozygote advantage Example: sickle-cell anemia & malaria A brief history of Ashkenazi Jews Observations on Ashkenazi Jew intelligence & disease • Hypothesis correlating intelligence & disease • Proposed evolutionary mechanisms • Alternative hypotheses Heterozygote Advantage (aka: overdominance) • A case in which heterozygotes have a higher fitness than homozygotes at a given locus. Maintains genetic polymorphism in a population. − e.g., sickle-cell allele & malaria tolerance − e.g., cystic fibrosis allele & TB resistance Distribution of sickle-cell anemia & malaria Green: regions with malaria Red stripes: regions with high frequency of sickle-cell trait Heterozygote Advantage Genotypes (S = wild-type allele, s = sickle-cell allele) SS: no sickle-cell trait, not malaria tolerant Ss: no sickle-cell disease, malaria tolerant ss: sickle-cell disease sickle-cell malaria Ashkenazi Jews: Observations • Have the highest average IQ test scores of any ethnic group (for which there are data). • During the 20th century, comprised ~3% of the U.S. population, but won 27% of Nobel prizes awarded to U.S. scientists. • Represent over half of the world chess champions. • High incidence of sphingolipid storage diseases: TaySachs, Gaucher, Niemann-Pick. • High incidence of certain cancers (DNA repair cluster mutations). Ashkenazi Jews: A brief history • 3 Jewish groups: Ashkenazi (blue), Middle Eastern (green), Sephardic (red) • Ashkenazi Jews (from Hebrew word for German) moved north of Alps in 1st millennium A.D. Settled in Rhineland during 800s. • In 12th & 13th centuries, expelled from Western Europe. Moved to Poland & Lithuania where Ashkenazi center remained for 5 centuries. Ashkenazi Jews: A brief history • In 19th & 20th centuries, large migration to W. Europe, Americas, Australia, & South Africa Sphingolipid Storage Diseases – neurological disorders Sphingolipids: A member of a class of lipids derived from the aliphatic amino alcohol sphingosine. They play an important role in signal transmission and cell-cell recognition. •Gaucher: accumulation of sphingolipid that promotes growth & branching of axons. •Niemann-Pick & Tay-Sachs: accumulation of sphingolipids that promote growth of dendrites. Hypothesis •Heterozygote advantage (e.g., Gaucher allele, recessive) – GG: wild-type – Gg: no disease, moderate increased linkage between brain cells yields increased intelligence – gg: Gaucher disease, increased linkage between brain cells yields increased intelligence (as measured by IQ tests) •Similar scenarios for heterozygotes with Niemann-Pick or Tay-Sachs alleles. Evolutionary mechanisms •Selective pressures − money-related occupations (e.g., banking, tax farming); today IQ and success are positively correlated in these professions •Assortative mating/no gene flow – Ashkenazim tend to marry among themselves Evolutionary mechanisms •Fitness – in Europe, prior to the 18th century, affluent families tended to have more children surviving to adulthood than poorer families •Effective population size – ~40% of Ashkenazi Jews are descended from 4 women living sometime in the last 2,000 yrs (Am. J. Hum. Gen. 2006, 78:487-97) Evolutionary mechanisms •Heritability of IQ – in youth “in impoverished families, 60% of the variance in IQ is accounted for by the shared environment, and the contribution of genes is close to zero; in affluent families, the result is almost exactly the reverse.” (Psych. Sci. 2003, 14:623-8) – in youth “past experiences…influence today’s IQ only because of their effect on past IQ and the effect of past IQ on today’s environment” (Psych. Rev. 2001, 108:346-69) – adult IQ largely affected by adult environment (Psych. Rev. 2001, 108:346-69) Alternatives to selection? •Genetic drift – evidence of genetic bottleneck •Diet – quantity of omega-3 fatty acids consumed by a pregnant mother greatly influences a child’s verbal IQ & social skills •Culture – education highly valued Potential Experiments • IQ tests controlled for genotypes • Environmental effect studies – dietary controls