The First Hominins

What happened

The lineages leading to humans and to chimpanzees split roughly 8 to 6 million years ago. Sahelanthropus tchadensis, from Chad and dated to about 7 million years ago, combines ape-like features (a small brain) with human-like ones (small canines, a skull that may indicate upright posture), and is among the oldest known members of the human family tree.

Why it matters

The first hominins mark the beginning of the human branch — the start of the roughly seven-million-year journey to our own species.

How we know

Whether Sahelanthropus is truly a hominin, and the exact timing of the human–chimpanzee split, are actively debated among scientists.

The status of the earliest claimed hominins and the precise date of the human–chimpanzee split are debated.

Sources

• Smithsonian Human Origins Program. Sahelanthropus tchadensis · Reputable source