Final answer:
Biological differences like skin color and disease predispositions are explained through genetics and evolutionary biology, with a greater emphasis on ancestry over racial categories. Genetic variation within human populations is greater than between them, and environmental factors significantly influence the distribution of traits and health outcomes.
Step-by-step explanation:
Biological differences such as skin color or a predisposition to certain diseases are largely explained through the study of genetics and evolutionary biology. Scientists explain that the vast diversity in human traits, like skin pigmentation and susceptibility to certain ailments, demonstrates the degree of genetic variation within the human species. Furthermore, modern genetic research has shown that categorizing populations strictly by race is not scientifically valid, as traits vary along spectrums with more genetic variation within so-called racial groups than between them.
The concept of race is often contested in science because only a limited number of genetic markers, like those controlling skin pigmentation, coincide with traditional racial categories. Instead, geneticists propose focusing on ancestry, which provides a more accurate understanding of the human genome's complexity and its implications on health. Environmental and social factors also play crucial roles in health outcomes, demonstrating the need to consider a holistic set of variables when examining how diseases and traits are distributed across human populations.
For instance, the global variation in skin color is largely attributable to an evolutionary response to varying levels of ultraviolet (UV) radiation from the sun, with darker skin providing protection in areas with intense sun exposure, and lighter skin being advantageous in regions with less sunlight to facilitate vitamin D synthesis. This illustrates how phenotypic characteristics can arise as adaptive traits in response to specific environmental pressures over thousands of years.