Question

How can skin color have a different heritability at different times of the year?

Short answer

Skin color's heritability can appear to change throughout the year due to the varying influence of environmental factors, particularly sunlight exposure. During times of intense sunlight (like summer), increased melanin production can darken the skin, reducing the perceived genetic influence (lower heritability). In contrast, during times of less sunlight (like winter), the environmental influence lessens and the genetic influences on skin color might seem more prominent (higher heritability).

Step-by-step solution

Understanding heritability

Heritability is the measure of how much a parent's traits can be passed on to their offspring genetically. In biology, this does not mean a 1:1 transfer, but rather how much of the variation in a trait (like skin color) can be attributed to genetic inheritance versus environmental influences.

Recognizing the Impact of Environment on Skin Color

In terms of skin color, it can be influenced not only by genetics but also by the environment. One major environmental influence is sunlight. The body produces more melanin, the pigment that gives skin its color, when it is exposed to more sunlight. This can cause the skin to darken, a phenomenon known as tanning. This environmental impact means that the heritability of skin color can vary depending on the time of year and the intensity of sunlight exposure.

Understanding Variability in Heritability

As sunlight exposure varies throughout the year, so does the impact on skin color. During periods of high sunlight exposure, like summer, the environmental influence on skin color is strong, possibly resulting in a lower heritability as the variation in skin color is less related to genetics and more to the environment. During periods of low sunlight exposure, like winter, the environmental influence decreases, so the genetic component's influence may seem stronger, potentially resulting in a higher heritability for skin color.