We are primates. One way to learn about humans is to study them as a kind of primate. This works especially well to explain how we got the physical structure that we have. It works a little bit to explain a few of our behaviors. It doesn't work at all to explain our culture. The Darwin tubercle is a projection on the helix of the ear resulting from a thickening of the cartilage. The actual size of the tubercle varies. It is one of many vestiges of our primate ancestry.