The allele of the human transport protein associated with lighter skin is found almost exclusively in people with European ancestry. The other common allele for darker skin, which appears to be the ancestral allele, is found in people with African ancestry. What is a plausible explanation for how the lighter-skin allele came to be so common in those with European ancestry?

Verified step by step guidance

1. Understand the concept of natural selection and adaptation. Natural selection is a process where individuals with traits better suited to their environment tend to survive and reproduce more than those without those traits. Over generations, these traits become more common in the population.
2. Consider the environmental differences between Europe and Africa. Europe generally has lower levels of sunlight compared to Africa. This difference in sunlight exposure is crucial for understanding skin color variation.
3. Recognize the role of vitamin D and sunlight. Vitamin D is essential for human health, and one of its sources is synthesis in the skin through exposure to sunlight. In areas with less sunlight, like Europe, lighter skin would be advantageous for more efficient synthesis of vitamin D.
4. Link the mutation for lighter skin to a survival advantage in Europe. A mutation causing lighter skin would allow individuals in sunlight-deficient regions to synthesize vitamin D more efficiently, thus having a selective advantage in terms of health and reproductive success.
5. Acknowledge the genetic drift and founder effect. Besides natural selection, these genetic mechanisms could also play a role in increasing the frequency of the lighter-skin allele among European populations. Genetic drift refers to random changes in allele frequencies, and the founder effect occurs when a new population is established by a very small number of individuals from a larger population.

Key Concepts

Natural Selection

Natural selection is a process where organisms better adapted to their environment tend to survive and produce more offspring. In the context of skin color, lighter skin may have provided a selective advantage in regions with lower sunlight, facilitating better vitamin D synthesis, which is crucial for bone health and immune function.

Genetic Drift

Genetic drift refers to random changes in allele frequencies within a population, which can lead to significant differences over time, especially in small populations. The prevalence of the lighter-skin allele in European populations may have been influenced by genetic drift, particularly in isolated communities where certain traits became more common purely by chance.

Migration and Gene Flow

Migration and gene flow involve the transfer of genetic material between populations. As humans migrated out of Africa and settled in Europe, the mixing of populations could have introduced the lighter-skin allele, which, combined with environmental factors, may have led to its increased frequency in European ancestry.