The shifting definition of what it means to be a hominid
We often think of human evolution as a straight line, but the scientific labels for our family have undergone massive revisions. From being a term used only for humans to a broad category including all great apes, the taxonomy of Hominidae is a complex, moving target.
The classification of the family Hominidae, or the great apes, has been a subject of significant taxonomic debate. Historically, the term 'honomid' was used restrictively to refer only to humans and their extinct relatives. However, by the 1990s, the definition expanded to include all great apes, such as chimpanzees, gorillas, and orangutans. Today, the term 'hominin' has largely taken over the older, more restrictive meaning, specifically referring to humans and our closest relatives like the genus Pan.
The evolutionary history of this group is better described as a 'family bush' than a simple lineage. While the exact identity of the most recent common ancestor remains unknown, molecular evidence suggests a series of key divergences. The lineage of the 'lesser apes' (gibbons) split from the great apes roughly 12 to 18 million years ago. Later, the ancestors of orangutans diverged from the line leading to other great apes about 12 million years ago. Within the Homininae subfamily, the lineages for gorillas and chimpanzees split from the human line between 8 and 4 million years ago.
Defining the boundaries of the human tribe, Hominini, remains scientifically complex. Some researchers suggest membership requires sharing more than 97% of the modern human genome and exhibiting capacities for language or culture. A particularly controversial criterion is the 'theory of mind'—the ability to attribute mental states like empathy or even deception to others. While humans develop this around age four to four and a half, it has not been proven or disproven for chimpanzees or gorillas, making the exact limits of our closest relatives a subject of ongoing debate.
Source: Hominidae
