Cotton-topped tamarins are small primates with tufts of long white hair on their heads. While studying these creatures, researchers noticed that males with longer hair get more opportunities to mate and father more offspring. Which of the following research questions would best test the hypothesis that having longer hair is adaptive in these males?

Question

A. test whether males with shaved heads are still able to mate
B. test whether other traits in these males are also adaptive
C. look for evidence of hair in ancestors of tamarins
D. determine if hair length is heritable

Answer 1

To best test the hypothesis that having longer hair is adaptive in male cotton-topped tamarins, the most relevant research question is:

A. test whether males with shaved heads are still able to mate.

This option directly examines the relationship between hair length and mating success, allowing researchers to determine if the loss of hair affects mating opportunities. If males with shaved heads experience a significant decrease in their ability to mate compared to those with longer hair, it would provide strong evidence that longer hair is indeed adaptive in increasing mating success.

The other options, while potentially interesting, do not directly address the hypothesis:

• B. investigates other traits, which is not focused on hair length.
• C. looks at evolutionary history without directly testing the current adaptive significance of hair length.
• D. evaluates heritability, which is important but does not test the adaptive function of the trait in the current context.