It is difficult to define Primates according to the presence or absence of certain distinguishing anatomical or behavioral traits. What *really* defines Primates is that they all are descended from a single common ancestor approximately 65 million years ago.

The correct answer is - true.

Explanation:

Primates are the third diverse group of mammals after rodents and bats. It is considered that it has diverged from other terrestrial mammals about 65 million years ago.

Defining and identifying the primates on the basis of certain anatomical and behavioral traits is not an easy task. There are almost 400 living species of primates are known.