History › Complex life › K–Pg mass extinction (asteroid impact)
First primates
c. 66–56 million years ago· Event· Life & early humans
Mostly agreedGood evidence; some details, dates or numbers uncertain.
Small tree-dwelling mammals with grasping hands and forward-facing eyes appeared: the ancestors of monkeys, apes and humans.
See it on the History map →What happened
Primates arose around the time the dinosaurs died out; a possible early relative, the squirrel-sized Purgatorius, lived in Montana about 66 million years ago. Life in trees favored grasping hands with nails, depth-perceiving vision and larger brains. By about 55 million years ago, recognizable primates lived across North America, Europe and Asia. Apes split from monkeys roughly 25–30 million years ago.
Why it matters
Hands, eyes and brains shaped by life in trees were later put to use by humans for tool-making and planning.
How we know
Fossil teeth and bones such as Purgatorius from Montana and Teilhardina, about 56 million years old; genetic clocks comparing living primates.
Still debated
Whether primates began before or after the asteroid impact, and on which continent, is debated.
Connections (2)
▸First mammals gave rise to First primatesWell documented
The connection
Among small mammals, one group adapted to life in the branches, evolving grasping hands, sharper forward-facing vision and larger brains. These became the first primates, the line leading to monkeys, apes and humans.
When and how
Probably in North America or Asia, about 66–56 million years ago; fossils include Purgatorius from Montana.
How we know
Fossil teeth and skeletons, plus genetic comparisons of living mammals, place primates among early placental mammals, closest to tree shrews and colugos (gliding 'flying lemurs').
Debates and open questions
Which mammal group primates came from, and whether they split off before the asteroid impact, is debated.
▸First primates gave rise, via apes, to First hominins: apes that walk uprightWell documented
The connection
Primates gave rise to monkeys, and later to apes. In Africa, one ape lineage split from the ancestors of chimpanzees about 7–6 million years ago. Its members began walking upright on two legs, becoming the first hominins: the human branch of the family tree.
When and how
In Africa, about 7–6 million years ago; early hominin fossils come from Chad, Kenya and Ethiopia.
How we know
Fossils trace a series from early apes to upright walkers; DNA shows humans and chimpanzees share a common ancestor.
Debates and open questions
Which fossil species is the very first hominin, and why upright walking evolved, are still debated.