[1] This cusp is entirely absent in some individuals and present in others in a variety of forms.

Other related forms include ridges, pits, or furrows.

Later studies showed that the development of this trait is affected by multiple genes.

[2] Although it is sometimes referred to in textbooks as the Cusp of Carabelli, it is actually a tubercle, as it is may be made only of enamel, and may not contain dentin but never has a root underneath.

The Carabelli cusp is present in several archaic human species such as Neanderthals, and it is believed that it serves to reduce stress on the teeth by increasing their surface area.