Are you a hominid or a hominin? The answer depends on your textbook.
In biological taxonomy, a single suffix can change your entire evolutionary family tree. While we often use these terms interchangeably, the distinction between 'hominid' and 'hominin' reflects a massive shift in how scientists understand our relationship to the great apes.
The confusion stems from shifting classifications driven by genetic phylogeny. Historically, 'hominid' was used to describe the lineage leading to modern humans, excluding other great apes. However, modern science has expanded the definition. Today, 'hominid' refers to the broader family Hominidae, which encompasses all great apes: humans, chimpanzees, gorillas, and orangutans, along with their ancestors [S2:p3, S2:p7].
The term 'hominin' is more specific, referring to the tribe Hominini. Under the most common modern convention, this tribe includes humans (genus Homo) and our extinct relatives like Australopithecus, but excludes gorillas [S1:p1, S2:p3]. However, the boundaries are not universally settled. Some researchers, following the work of Camille Arambourg in 1948, define Hominini to include both humans and chimpanzees (genus Pan) [S1:p2, S1:p6]. Others use 'hominin' to refer strictly to the human side of the evolutionary split, excluding Pan [S1:p7].
These taxonomic debates are fueled by new evidence. For instance, the 2000 discovery of Orrorin tugenensis, dated to 6.2 million years ago, briefly challenged the idea that humans evolved directly from australopithecines [S1:p11]. Furthermore, the divergence between the human and chimpanzee lineages was likely not a clean break but a complex process of hybridization that may have lasted as recently as 4 million years ago [S1:p10]. As genetic techniques improve, the tree of life continues to be redrawn, leaving students and even scientists to navigate a landscape of overlapping and competing definitions [S2:p4, S2:p6].
Source: Hominini
