Final answer:
Hominoids encompass all great apes and humans, whereas hominins include humans and their direct ancestors after diverging from chimps. The genus Homo appeared around 2.8 million years ago with evolutionary traits like bipedalism and larger brains.
Step-by-step explanation:
The term hominoid refers to the group that includes all modern and extinct great apes, such as humans, gorillas, chimpanzees, and orangutans, as well as their ancestors. On the other hand, the term hominin designates any human or human ancestor that evolved after the human lineage diverged from the chimpanzee lineage around 6 million years ago. This group includes not only our own species, Homo sapiens, but also extinct human species and all immediate ancestors, such as Homo habilis and Homo erectus, as well as the genera Australopithecus, Paranthropus, and Ardipithecus.
The genus Homo first appeared about 2.8 million years ago. Early representatives were fully bipedal but had smaller brains compared to modern humans. The genus Homo has evolved significantly over time, with an increase in brain size and a development of behaviors such as tool use.
Notably, bipedal locomotion is a characteristic behavioral complex shared by all hominins, separating them from other hominoids that may not walk upright. This evolution towards bipedalism has been a defining feature in the lineage of humans.