Final answer:
The order of mammals that includes prosimians, monkeys, apes, humans, and our ancient hominid ancestors is the Primates order. Humans are part of the Hominidae family within this order, which is characterized by bipedalism, larger brain size, and opposable thumbs. The genus Homo, part of the hominids, first appeared about 2.8 million years ago.
Step-by-step explanation:
The order of mammals that includes prosimians, monkeys, apes, and humans, as well as our ancient hominid ancestors, is the Primates order. This diverse group encompasses lemurs, tarsiers, and both New World and Old World monkeys, as well as the great apes and humans. Among the various families within this order, humans, along with chimpanzees, gorillas, and orangutans, are classified in the family Hominidae, commonly referred to as hominids. This family is of particular interest because it helps us understand the evolution of our own species, Homo sapiens. Hominids are characterized by traits such as bipedalism, increased brain size, and a fully opposable thumb.
Tracing back the hominid lineage, it is found that the genus Homo first evolved about 2.8 million years ago with species that were fully bipedal but had small brains, all of which are now extinct. The term 'hominin' refers to species after the divergence from our common ancestor with chimpanzees about six million years ago, including many evolutionary branches that contribute to our understanding of human evolution.