Jan Simek, University of Tennessee
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When and how was walking invented? – Rayssa, 11, Newark, New Jersey
This is an important question because many anthropologists consider bipedalism – which means walking on two legs – as one of the defining characteristics of “hominins”, or modern humans, and their ancestors. However, it is difficult to give a simple answer, because bipedalism did not appear one day. It has undergone a gradual evolution that began millions of years ago.
Of course, there are no video clips of the first person walking up and down. So how do scientists attempt to answer questions about how people moved through the 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 points to how ancient people walked.
In 1994, the first fossils of an unknown hominid were discovered in Ethiopia. Anthropologists who found the remains called the new find an adult female, Ardipithecus ramidus, nicknamed “Ardi”. Over the next 10 years, more than 100 fossils of the Ardi species were found and dated to between 4.2 million and 4.4 million years ago.
When scientists examined this collection of bones, they identified some characteristics that indicate bipedalism. The foot, for example, had a structure that allowed for the kind of toe push that we have today that four-legged monkeys don’t. The shape of the pelvic bones, the way the legs were positioned below the pelvis, and the way the leg bones interlocked also suggested standing walking. Ardi may not have walked exactly the way we do today, but bipedalism as a normal mode of travel seems to be characteristic of these fossils from 4.4 million years ago.
Anthropologists had already found the nearly 40% complete skeleton of a species of hominid that lived about a million years after Ardi, also in Ethiopia. Due to its similarity to other fossils found in southern and eastern Africa, they called it Australopithecus afarensis, which in Latin means “ape from the south of the far region”. This individual was female, so they nicknamed him “Lucy” after a Beatles song that was popular at the time.
Many other fossils of this species – over 300 individuals – were added to the group, and today researchers know a lot about Lucy and her relatives.
Lucy had a partial but well-preserved pelvis, which is how anthropologists knew she was a woman. The pelvis and the bones of the upper part of the leg interlock in a way that shows that she was walking upright on two legs. No foot bones have been preserved, but later discoveries of A. afarensis include feet and also indicate bipedal walking.
In addition to the fossil remains, scientists have found other remarkable evidence of how Lucy’s species moved around the Laetoli site in Tanzania. Under a layer of volcanic ash dating back to 3.6 million years ago, anthropologists found fossilized footsteps in what had once been a wet surface of volcanic ash. The tracks stretch for nearly 100 feet, and 70 individual footprints indicate the presence of at least three individuals walking upright on two feet. Considering the presumed age, the manufacturers were probably Australopithecus afarensis.
The traces prove that these hominids walked on two legs, but the gait seems a little different from ours today. Yet Laetoli provides strong evidence for bipedalism 3.5 million years ago.
A hominid whose anatomy so resembled ours that it can be said that he walked like us did not appear in Africa until 1.8 million years ago. homo erectus was the first to have the long legs and shorter arms that would have made it possible to walk, run and move around the landscapes as we do today. homo erectus also had much larger brains than earlier bipedal hominids and made and used stone tools called Acheulean instruments. Anthropologists consider homo erectus our close relative and one of the first members of our own kind, Homo.
So, as you can see, the human walk took a very long time to develop. It appeared in Africa more than 4.4 million years ago, long before the emergence of tool making.
Why did hominids walk upright? Maybe it made it easier for them to see predators, or to run faster, or maybe the environment changed and there were fewer trees to climb like previous hominids did.
In any case, humans and their ancestors began to walk very early in their evolutionary history. Even though bipedalism predates tool making, an upright posture freed up the hands to make and use tools, which eventually became a hallmark of humans like us.
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Jan Simek, professor of anthropology, University of Tennessee
This article is republished from The Conversation under a Creative Commons license. Read the original article.