Scleral pigmentation leads to conspicuous, not cryptic, eye morphology in chimpanzees

Gaze following has been argued to be uniquely human, facilitated by our depigmented, white sclera [M. Tomasello, B. Hare, H. Lehmann, J. Call, J. Hum. Evol. 52, 314-320 (2007)]-the pale area around the colored iris-and to underpin human-specific behaviors such as language. Today, we know that great apes show diverse patterns of scleral coloration [J. A. Mayhew, J. C. Gómez, Am. J. Primatol. 77, 869-877 (2015); J. O. Perea García, T. Grenzner, G....