Field experiments find no evidence that chimpanzee nut cracking can be independently innovated.

Cumulative culture has been claimed a hallmark of human evolution. Yet, the uniqueness of human culture is heavily debated. The zone of latent solutions hypothesis states that only humans have cultural forms that require form-copying social learning and are culture-dependent. Non-human ape cultural behaviours are considered 'latent solutions', which can be independently (re-)innovated. Others claim that chimpanzees, like humans, have cumulative culture. Here, we use field experiments at Seringbara (Nimba Mountains, Guinea) to test whether chimpanzee nut cracking can be individually (re-)innovated. We provided: (1) palm nuts and stones, (2) palm fruit bunch, (3) cracked palm nuts and (4) Coula nuts and stones. Chimpanzee parties visited (n = 35) and explored (n = 11) the experiments but no nut cracking occurred. In these experiments, chimpanzees did not individually (re-)innovate nut cracking under ecologically valid conditions. Our null results are consistent with the hypothesis that chimpanzee nut cracking is a product of social learning.

Placentophagy in wild chimpanzees (Pan troglodytes verus) at Bossou, Guinea.

Despite intensive observation of nonhuman great apes during long-term field studies, observations of great ape births in the wild are rare. Research on wild chimpanzees (Pan troglodytes verus) at Bossou in the Republic of Guinea has been ongoing for 35 years, yet chimpanzee parturitions have been observed on only two occasions. Here we provide information regarding both chimpanzee births, with detailed information from the close observation of one. During this birth, the mother built a day nest in a tree before parturition. After giving birth, the mother consumed the placenta, and the other chimpanzees in her party gathered near her and her neonate. However, she did not share the placenta, and consumed it all herself. In the second observation, the mother also built a nest in a tree and subsequently gave birth. Thereafter, she shared the placenta with some individuals and consumed part of the placenta herself. Although maternal placentophagy is a ubiquitous behavior among the majority of non-human primates, observations of placenta sharing by wild primates are infrequent, and the proximate and ultimate explanations for the behavior remain unclear.