Smithsonian.com

An artist’s reconstruction of Australopithecus afarensis, a species that can be called a hominid or a hominin. Image courtesy of Wikicommons

If you follow news about human evolution, you’ve probably noticed that our ancestors are increasingly called hominins rather than hominids. Why the change? It’s the result of researchers revising how they classify primates.

The system of taxonomy that biologists use to categorize animals, plants, bacteria and other organisms is based on the work of the 17th-century scientist Carl Linnaeus. It consists of nested, hierarchical groups that get more and more narrow as you go down the taxonomic chain. To understand what the terms hominins and hominids mean, let’s first look at the traditional classification of modern humans.

Kingdom: Animalia

Phylum: Chordata (animals that have a notochord at some point in their lives; in fish, reptiles, birds and mammals, the notochord becomes the vertebral column)

Class: Mammalia

Order: Primates (lemurs, bush babies, tarsiers, monkeys, apes and humans)

Family: Hominidae (modern humans and our close extinct relatives, such as Ardipithecus and Australopithecus)

Genus: Homo

Species: sapiens

Under this system, the term hominid refers to members of the Hominidae family (in taxonomy, names that end in -idae refer to a family). But in the past few decades, the definition of Hominidae has been broadened to include orangutans, gorillas and chimpanzees because of the recognition that these apes are very closely related to humans. In the past, they had their own family—Pongidae—based on the physical characteristics that seemed to unite the great apes as a group. Genetic analyses, however, indicated that gorillas and chimpanzees are actually more closely related to humans than they are to orangutans. Therefore, the Pongidae family didn’t make sense (in technical terms, it was paraphyletic). The genetic discoveries led to a new classification of humans, starting at the family level.

Family: Hominidae (orangutans, gorillas, chimpanzees and humans)

Subfamily: Homininae (gorillas, chimpanzees and humans)

Tribe: Hominini (humans and our close extinct relatives; the group that was called Hominidae in the previous classification)

Genus: Homo

Species: sapiens

Here, the term hominin refers to the tribe Hominini. That’s why many of our extinct ancestors are now called hominins. But it’s not technically wrong to call them hominids—all members of Hominini are also members of the subfamily Homininae and the family Hominidae, that’s how the nesting system works. It’s just a less precise term.

At Hominid Hunting, we generally use the term hominid in the traditional sense of the word: humans and their close extinct ancestors. But rather than being old-fashioned, I think it means we’re allowed to write about chimpanzee, gorilla or orangutan evolution from time to time.