The genetics of race can be more complex than simple Mendelian inheritance due to a variety of factors.
Polygenic inheritance: Race is determined by multiple genes, each with multiple alleles, which may interact with each other in complex ways.
Environmental factors: The expression of genes may be influenced by environmental factors such as diet, climate, and exposure to toxins, which can differ between populations.
Epigenetics: Epigenetic modifications, such as DNA methylation, can affect gene expression without changing the underlying DNA sequence. These modifications can be influenced by environmental factors and can differ between populations.
Genetic drift: Over time, random genetic mutations can accumulate in isolated populations, leading to genetic differences that are not related to adaptive traits.
Admixture: Many populations have been shaped by admixture, or the interbreeding of different populations, which can result in complex patterns of genetic variation.
Population structure: Genetic differences between populations may be influenced by historical factors such as migration, colonization, and population bottlenecks, which can create complex patterns of genetic structure.
All of these factors can make it difficult to define race in purely genetic terms and to draw clear boundaries between different racial groups.