Final answer:
The assertion that there are no clear-cut biological races in humans is true, as both the variation of human traits and genetic studies display more diversity within supposed racial groups than between them.
Step-by-step explanation:
It is true that there are no clear-cut biological races of human beings. The concept of race has been shown by biological anthropologists, such as AgustÃn Fuentes and Nina Jablonski, to be scientifically inaccurate. Human traits like skin color, facial features, hair texture, and blood type do not cluster into discrete racial categories; instead, they vary along a spectrum and are mixed among populations.
For instance, while skin color is often used to assign racial categories, research by Jablonski shows that skin tone varies widely among humans and is linked to evolutionary adaptations related to ultraviolet light exposure and vitamin D synthesis. Furthermore, from a genetic perspective, the human genome project revealed that there is more variation within so-called racial groups than between them, undermining the notion of distinct biological races.