Now, what do we mean by a highly variable trait? Well, let's consider the following example. Let's examine a trait in humans we call the eye color. Now, we know that the colors of our eyes varies from one individual to another individual. Someone might have hazel eyes another person might have blue eyes or green eyes or gray eyes or brown eyes. So we have many different types of variations for that particular trait and that's precisely what makes that trait highly variable in humans.