Where did we come from? Anthropology's answer, built from fossils, stone tools and DNA, is one of the great detective stories of science. This level follows how evolution by natural selection produced us. Much of the story is still being revised as new finds turn up, so treat every date here as an estimate with a margin of error.

Cousins, not descendants

Humans are primates, and our closest living relatives are chimpanzees and bonobos. A common misunderstanding is that humans evolved from chimpanzees. They did not. Humans and chimpanzees share a common ancestor that lived roughly 6 to 7 million years ago, and both lines have been evolving separately ever since. Scientists use the word hominin for humans and all extinct species more closely related to us than to chimpanzees.

The old picture of evolution as a march, with a hunched ape slowly straightening into a modern man, is also misleading. Human evolution looks more like a branching bush than a ladder. At several points in the past two or more hominin species lived at the same time, and most branches ended without descendants.

Walking first, thinking later

For a long time scientists assumed that a big brain came first and everything else followed. The fossils told a different story: upright walking on two legs, called bipedalism, appeared millions of years before large brains. In 1974 researchers in Ethiopia found a partial skeleton about 3.2 million years old, nicknamed Lucy, of the species Australopithecus afarensis. Lucy's hips and legs show she walked upright, yet her brain was about the size of a chimpanzee's. At Laetoli in Tanzania, footprints pressed into volcanic ash around 3.6 million years ago show the same thing: a striding upright gait long before big brains.

The search was also marked by error. The Piltdown Man fossil, announced in England in 1912, seemed to show a large brain with an apelike jaw, exactly what many experts expected. In 1953 Piltdown was exposed as a forgery that combined a human skull with an orangutan jaw. The hoax is a lesson in how expectations can blind experts, and in how testing eventually corrects them.

Tools, fire and travel

Stone tools are among the oldest evidence of culture. Simple flaked tools called Oldowan, after Olduvai Gorge in Tanzania, date to about 2.6 million years ago, and finds in Kenya announced in 2015 suggest even older tools around 3.3 million years ago. The species Homo erectus, which appeared by about 1.9 million years ago, had a body much like ours below the neck and made carefully shaped hand axes. Homo erectus was the first hominin known to spread beyond Africa, reaching what is now Georgia by about 1.8 million years ago and later East Asia. When hominins first controlled fire is debated, with proposed dates ranging from about a million years ago to a few hundred thousand.

Our own species

Fossils from Jebel Irhoud in Morocco, dated in 2017 to about 300,000 years ago, are among the oldest known members of Homo sapiens. The weight of fossil and genetic evidence supports the Out of Africa model: modern humans arose in Africa and later spread across the rest of the world, with a major dispersal roughly 60,000 to 70,000 years ago. Its main rival, the multiregional model, held that modern humans evolved in parallel on several continents; the genetic evidence has largely, though not entirely, favored the African origin. Charles Darwin had suggested in 1871 that Africa was the likeliest birthplace of humanity, long before the fossils were found.

Spreading humans met other kinds of humans. Neanderthals lived in Europe and western Asia until about 40,000 years ago. Ancient DNA studies led by Svante Pääbo, who received a Nobel Prize in 2022, showed that people with ancestry from outside Africa carry roughly 1 to 2 percent Neanderthal DNA, evidence that the groups interbred. A finger bone from Denisova Cave in Siberia revealed another group, the Denisovans, known mostly from their genes. Our species is the last survivor of a once crowded family.

What this means for race

Because modern humans are a young species descended from a fairly small founding population, we are genetically very similar to one another. In 1972 the geneticist Richard Lewontin found that most human genetic variation, around 85 percent, lies within populations rather than between them. Traits like skin color change gradually across geography, mostly tracking the strength of sunlight, rather than falling into a few sharp boxes. Biology does not support the old idea of a handful of distinct human races. That finding does not create equal human worth, which rests on moral grounds, but it removes one of the oldest excuses for denying it.

Worked example: reading a new fossil

Suppose a team finds a hip bone and a skull fragment in Kenyan rock dated to about 3 million years ago. The hip is broad and bowl shaped, built for balancing a body over two legs. The skull fragment suggests a small braincase. The team concludes that this creature walked upright with an apelike brain, fitting the pattern Lucy revealed. They avoid calling it a "missing link", because evolution is a bush with many branches, and they cannot yet tell whether this species is our ancestor or a cousin whose line ended. They publish the dates with ranges of error, share casts of the bones, and invite other teams to test their reading.