Final answer:
Humans (Homo sapiens) are the primate group classified as hominins. The term hominin is used for species that are more closely related to humans than to any other apes, and it includes traits like bipedalism and a larger brain size.
Step-by-step explanation:
The primate group classified as hominins is humans. Hominins refer to all species that are considered to be in the direct lineage to humans, including the genera Homo, Australopithecus, Paranthropus, and Ardipithecus. The term is distinct from 'hominids,' which includes all modern and extinct great apes, such as gorillas, chimpanzees, and orangutans, as well as humans. However, when asked which among the provided options (bonobos, gorillas, humans, gibbons, orangutans) is a hominin, the answer is humans, i.e., Homo sapiens.
It's important to note that humans share over 97% of their DNA with gorillas and chimpanzees, but the defining characteristics of hominins include bipedal locomotion and other markers such as an increase in brain size and a fully opposable thumb. While bonobos, gorillas, orangutans, and gibbons are all part of the Hominidae family, they are not classified as hominins.