Skin deep: The decoupling of genetic admixture levels from phenotypes that differed between source populations

Area of Science:

• Population Genetics
• Quantitative Genetics
• Human Ancestry Studies

Background:

• Genetic admixture involves source populations with distinct genotype and phenotype patterns.
• Phenotypes initially linked to ancestral background are often used as ancestry markers in admixed populations.
• These phenotype-ancestry correlations can influence social categorizations but may not persist.

Purpose of the Study:

• To understand the joint dynamics of admixture levels and phenotype distributions in admixed populations.
• To investigate how genetic ancestry and phenotypic traits evolve over time.
• To determine the reliability of phenotypes as proxies for genetic ancestry.

Main Methods:

• Devised a mechanistic model integrating admixture, quantitative trait, and mating models.
• Analyzed the model's behavior in relation to its parameters.
• Simulated the decoupling of genetic ancestry and phenotype over generations.

Main Results:

• Decoupling of genetic ancestry and phenotype can occur rapidly.
• This dissociation is faster when phenotypes are influenced by fewer genetic loci.
• Positive assortative mating slows the dissociation process compared to random mating.

Conclusions:

• Traits initially differing between source populations may only be reliable ancestry proxies for a limited time.
• The reliability decreases if traits are determined by few loci.
• Social categorizations based on such traits become less informative about genetic ancestry over time.