FST in humans is relatively low, indicating more genetic variation within populations than between them, supporting common ancestry. So, the correct choice is option a.
The statement is likely referring to FST (Fixation Index), a measure of population genetic structure. FST values range from 0 to 1, where low values indicate less genetic differentiation between populations. If FST in humans is relatively low, it implies that there is much genetic variation within populations compared to the variation between populations.
In other words, the majority of genetic diversity is found within local groups rather than being distinct between different populations. This aligns with the concept that human genetic diversity is primarily a result of individual variations within populations rather than stark differences between populations, supporting the idea of a common ancestry for human populations.
Therefore, option a is the correct choice.