Hominin fossils that reveal clues to the emergence of Homo sapiens are rare in Africa, but in combination with studies of modern human genomes, researchers are piecing together an ever more complex timeline of human history.
Genomic analyses suggest that the majority of people living outside Africa today trace most of their ancestry back to a single migration event of a small group of modern humans who left Africa between 60,000 and 70,000 years ago.
Some analyses of modern human genomes hint that Homo sapiens may have interbred with other hominins in Africa.
Comparing ancient DNA from Neanderthals and Denisovans with modern human genomes has revealed that modern humans interbred with these other hominin groups.
SAHELANTHROPUS, ORRORIN, ARDIPITHECUS SPP.
Members of these relatively small-brained genera probably emerged not long after the human-chimpanzee divergence, and are the first known species of apes that habitually walked upright.
This diverse group exhibited both ape- and human-like characteristics. Some species are thought to have used stone tools and to have evolved into the genus Homo.
EARLY HOMO SPECIES
Hominins of the genus Homo shared distinctly small back teeth, which experts think allowed them to consume diverse diets. One species of early Homo evolved into Homo erectus.
Homo erectus may have been the first hominin to wield fire and stone axes. The species spread across Asia, where it continued to evolve. In Africa, it gave rise to Homo heidelbergensis.
Named after its initial discovery near Heidelberg, Germany, fossils similar to Homo heidelbergensis were later found to also occur in Africa. It routinely hunted large animals and may have built dwellings made of wood or rock.
HOMO FLORESIENSIS AND HOMO LUZONENSIS
Researchers have recently discovered two small hominin species on Pacific islands, Homo floresiensis on Flores in Indonesia and Homo luzonensis in the Philippines.
Only known from skeletons found in South Africa, this species had a remarkably tiny brain but modern-human–like features such as the shape of its teeth and possibly the habit of burying its dead.
Compared with modern humans, Neanderthals had shorter, stockier skeletons and larger noses, but their brains were just as large, if not larger.
Denisovans, only known from from ancient DNA and a handful of bones and teeth, were closely related to Neanderthals.
Eventually, the hallmarks of our own species—exceptionally large brains, flat faces, and small jaws—appear in the fossil record. Genetic studies suggest that H. sapiens started to split into several major lineages of modern humans more than 200,000 years ago.
Excavating a continent
A number of researchers suspect that Homo sapiens arose not in a single place in Africa, but across the entire continent, emerging from a network of interconnected hominin populations. But for decades, archaeologists positioned East and South Africa as important places for hominin evolution and the putative birthplace of our species. That’s likely because most fossils, including groundbreaking findings that have transformed our understanding of human evolution, have been found in those regions.
KABWE, ZAMBIA, 1921
“Kabwe skull,” 300,000 years ago
Also called “Broken Hill skull,” the specimen is considered a representative of Homo heidelbergensis.
NEAR SAFI, MOROCCO, 1961
Human remains at Jebel Irhoud, 315,000 years ago
Flint blades and Homo sapiens–like skeletons in a Moroccan cave known as Jebel Irhoud may represent the oldest Homo sapiens artifacts. The skeletons have modern features such as round skulls and modern-human–like teeth and faces.
OMO NATIONAL PARK, ETHIOPIA, 1967-1974
Omo Kibish remains, 195,000 years ago
Fragments from two skulls, four jaws, a legbone, a few hundred teeth, and some other bones were found at a site in Ethiopia, and are classified as anatomically modern Homo sapiens.
AFAR REGION, ETHIOPIA, 1974
“Lucy,” 3.2 million years ago
Lucy—the skeletal remains of an Australopithecus afarensis female—is one of the best-known hominin fossils. Studies suggest that she was both tree-dwelling and capable of an upright gait, providing an important evolutionary stepping stone from more primitive ape species to modern humans.
LAKE TURKANA, KENYA, 1984
“Turkana Boy,” 2 million years ago
A nearly complete skeleton of an ancient Homo erectus child found near Kenya’s Lake Turkana provides a rare glimpse into how quickly this species reached adulthood and how similar their skeletons were to ours.
RISING STAR CAVE, SOUTH AFRICA, 2013
Homo naledi, 236,000–335,000 years ago
In 2013 and 2014, cavers found skeletons of two adults and one juvenile of what is believed to be a new species: Homo naledi. Its tiny brain and ape-like shoulders—indicating it was a good climber—suggest it may be an evolutionary off-shoot lineage that went extinct.
AFAR REGION, ETHIOPIA, 2013
Adult jawbone, 2.8 million years ago
A mandible fragment is the earliest known trace of the genus Homo, although the species it belongs to is a mystery.
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