Three upright walkers, including Lucy (center) and two copies of Australopithecus sediba, a human ancestor from South Africa who is nearly 2 million years old.
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When and how was walking invented? – Rayssa, 11, Newark, New Jersey
This is an important question as many anthropologists view two-leggedness – that is, walking on two legs – as one of the defining characteristics of “hominins” or modern humans and their ancestors. It is difficult to give a simple answer, however, since two-leggedness did not appear just one day, but it went through a gradual development that began many millions of years ago.
Of course, there are no video clips of the first person ever walking upright. So how do scientists try to answer questions about how people moved in the very ancient past? Fortunately, the shape of a creature’s bones and the way they fit together can tell the story of how that body moved when it was alive. And anthropologists can find other evidence in the landscape that suggests how the ancient people walked.
In 1994 the first fossils of an unknown hominin were found in Ethiopia. The anthropologists who found the remains called the new discovery an adult female individual, Ardipithecus ramidus, nicknamed “Ardi”. 4.2 million and 4.4 million years old.
When scientists examined this collection of bones, they identified certain features that suggest bipedalism. The foot, for example, had a structure that enabled the kind of toe-off we have today that four-legged monkeys don’t. The shape of the pelvic bones, the position of the legs under the pelvis, and the fit of the leg bones also indicated walking upright. It may be that Ardi did not run exactly as we do today, but the two-leggedness as normal locomotion seems to be characteristic of these fossils 4.4 million years ago.
Anthropologists had already found the almost 40% complete skeleton of a hominin species that roughly lived a million years after Ardi, also in Ethiopia. Because of its similarity to other fossils found in South and East Africa, they named it Australopithecus afarensiswhich means “southern monkey from afar” in Latin.
Many more fossils of this type – more than 300 individuals – were added to the group, and researchers today know quite a bit about Lucy and her relatives.
A picture of a model based on Lucy and others Australopithecus afarensis Skeletal fossils found in East Africa in 1974.
Lucy had a partial but well-preserved basin, which is why anthropologists knew she was female. The pelvic and thigh bones fit together in a way that has been shown she walked upright on two legs. No foot bones were preserved, but later discoveries from A. afarensis include feet and also indicate two-legged walking.
In addition to fossil remains, scientists found other notable evidence how Lucy’s species moved at the Laetoli site in Tanzania. Under a layer of volcanic ash from 3.6 million years ago, anthropologists found fossilized footprints in a once damp surface of volcanic ash. The tracks extend over almost 30 meters and 70 individual prints indicate the presence of at least three people walking upright on two legs. Given the presumed age, the makers were likely Australopithecus afarensis.
The tracks show that these hominins walked on two legs, but the walk seems a little different today than ours. Still, Laetoli offers solid evidence of two-leggedness 3.5 million years ago.
A hominin whose anatomy was so similar to our own that we can say he walked like us only appeared in Africa 1.8 million years ago. Homo erectus was the first with long legs and shorter arms that would have made it possible to walk, run and Move through the landscapes of the earth like we do today. Homo erectus also had a much larger brain than previous two-legged hominins and made and used stone tools called Acheulean implementations. Consider anthropologists Homo erectus our close relative and an early member of our own species, homo.
As you can see, human walking has evolved for a very long time. It appeared in Africa more than 4.4 million years ago, long before tool making emerged.
Why did hominins walk upright? Maybe it made it easier for them to see predators or run faster, or maybe the environment changed and there were fewer trees to climb than previous hominins.
In any case, humans and their ancestors started walking very early in their evolutionary history. Although two-leggedness came before toolmaking, an upright posture freed the hands to make and use tools, which ultimately became one of the hallmarks of people like us.
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