Hominidae

Hominidae, commonly called great apes, is a primate family with eight living species spread across four genera. These are *Pongo* (covering the Bornean, Sumatran, and Tapanuli orangutans), *Gorilla* (eastern and western gorillas), *Pan* (chimpanzees and bonobos), and *Homo* (which now only includes modern humans, *Homo sapiens*). The label "hominid" has shifted in meaning over time. It originally applied just to humans and their extinct close relatives, but by the 1990s it had expanded to cover all great apes. Today, the older, narrower sense is mostly carried by the term "hominin," which also includes the genus *Pan*. Even so, usage varies—some scientists and the public still use "hominid" in its original, human-focused way, and scholarly writing generally stuck with that tradition until around the year 2000.

Within Hominidae, several living and extinct genera fall into two subfamilies: Homininae groups humans, chimpanzees, and gorillas, while Ponginae contains the orangutans. The last common ancestor of all Hominidae lived roughly 14 million years ago, when orangutan ancestors split from the line leading to the other three genera. Earlier, the ancestors of Hominidae had already diverged from the gibbon family (Hylobatidae), likely 15 to 20 million years ago.

Because humans are so genetically close to other great apes, some animal rights groups—like the Great Ape Project—argue that nonhuman great apes should be considered persons with basic human rights. Twenty-nine countries have banned scientific testing on great apes to protect them.

**Evolution**

Around 22 million years ago, in the early Miocene, East Africa was home to many primitive, tree-adapted catarrhine species, hinting at a long prior history of diversification. Fossils from 20 million years ago include fragments of *Victoriapithecus*, the earliest known Old World monkey. Genera thought to belong to the ape lineage leading up to 13 million years ago include *Proconsul*, *Rangwapithecus*, *Dendropithecus*, *Limnopithecus*, *Nacholapithecus*, *Equatorius*, *Nyanzapithecus*, *Afropithecus*, *Heliopithecus*, and *Kenyapithecus*—all from East Africa.

Farther afield, other non-monkey catarrhines from the middle Miocene—such as *Otavipithecus* from Namibia, and *Pierolapithecus* and *Dryopithecus* from France, Spain, and Austria—show that a wide variety of ancestral apes lived across Africa and the Mediterranean basin during the warm, stable climates of the early and middle Miocene. The most recent of these far-flung Miocene apes is *Oreopithecus*, found in coal beds in northern Italy and dated to 9 million years ago.

Molecular evidence suggests that gibbons (the lesser apes, family Hylobatidae) split from the great apes between 18 and 12 million years ago, and orangutans (subfamily Ponginae) diverged from the other great apes about 12 million years ago. No fossils clearly document gibbon ancestry, which may have started from an unknown Southeast Asian hominoid population. Fossil proto-orangutans, dating to around 10 million years ago, might be represented by *Sivapithecus* from India and *Griphopithecus* from Turkey. Species close to the last common ancestor of gorillas, chimpanzees, and humans may be represented by *Nakalipithecus* fossils from Kenya. Molecular evidence indicates that between 8 and 4 million years ago, gorillas (*Gorilla*) and then chimpanzees (*Pan*) split from the human line. Human DNA is about 98.4% identical to chimpanzee DNA when comparing single nucleotide polymorphisms. The fossil record for gorillas and chimpanzees is sparse, likely due to poor preservation in acidic rainforest soils and sampling bias.

Other hominins probably adapted to drier environments outside the African equatorial belt, where they encountered antelope, hyenas, elephants, and other animals adapting to East African savannas, especially the Sahel and Serengeti. The wet equatorial belt shrank after about 8 million years ago, and there is very little fossil evidence for the split of the hominin lineage from gorillas and chimpanzees, which is thought to have occurred around that time. The earliest fossils some argue belong to the human lineage are *Sahelanthropus tchadensis* (7 Ma) and *Orrorin tugenensis* (6 Ma), followed by *Ardipithecus* (5.5–4.4 Ma), with species *Ar. kadabba* and *Ar. ramidus*.

**Taxonomy and Terminology**

The classification of great apes has been revised several times in recent decades, leading to varied use of the word "hominid." Originally, it meant only humans and their closest relatives—what is now called "hominin." The meaning of Hominidae gradually shifted, so that today "hominid" includes all great apes, including humans. Several similar terms apply to related classifications: a hominoid, sometimes called an ape, is a member of the superfamily Hominoidea, whose living members are the gibbons (lesser apes) and the great apes.