New study: An ancient species in the human lineage walked on two legs, but could not run as fast and efficiently as we do
Who would win in a running competition between a modern human and one of our ancient ancestors, who lived more than three million years ago? According to New researchThe answer is, without a doubt, modern man. We may not be as fast as many animals that run on all fours, but over the past millions of years, our movement on two legs has become very sophisticated. Our species has evolved not only to walk steadily on two legs, but also to run faster than our ancestors.
Walking on two legs probably appeared quite early in our lineage. One of the first pieces of evidence for this was discovered in 1974, when an international team of researchers uncovered Bones of a 3.2 million-year-old skeleton in EthiopiaThe researchers found about 40 percent of the skeleton's bones, a remarkable find considering its age: When it comes to fossils that are millions of years old, most of the finds are fragments of bones and single teeth. The skeleton belonged to a young female, nicknamed "Lucy" after the Beatles song "Lucy in a Sky of Diamonds," which was playing at the camp while the researchers were working on the finds. Her species was named Australopithecus afarensis (Australopithecus afarensis), meaning "southern ape from Afar," which is a region in Ethiopia. Lucy's leg and pelvic bones indicated bipedalism, even at this early stage of evolution.
Two years later and not very far away, in Latuli, Tanzania, she discovered Paleontologist Mary Leakey (Leakey) Footprints preserved in volcanic ash. The 3.7 million-year-old footprints were made by hominids, clearly walking on two legs. Researchers speculate that they were made by Australopithecus afarensis, the same species as Lucy.
Lucy walked on two.
Those ancient people, who lived more than three million years ago, were already walking upright on two legs. But did they also run like us? That's what the researchers tried to find out in the new study. To do this, they created a computer simulation, based on tools developed for studying the movement of living animals and humans. They inserted Lucy's reconstructed skeleton into it, and added muscles to it.
"We basically created a digital 'robot' of A. afarensis, with all the bones and muscles that determine running speed," said Carl Bates, who led the study. In an interview with the New Scientist website. They knew the structure of the bones, thanks to Lucy. But her muscles were not preserved. Since the researchers did not know what Australopithecus muscles looked like, they created several simulations: with muscles similar to those of a human, muscles similar to those of a chimpanzee, and all sorts of intermediate versions. Then they tested how their digital robot ran: what its maximum speed was, and how much energy it expended while running.
Video showing the simulations: https://www.youtube.com/embed/dJYNn_8AA8Q?si=G_p_5h5Y84F5MajQ
One of the findings from these simulations is how well our muscles are adapted for running on two legs. When the Australopithecus "robot" was equipped with human-like muscles in the calf, with a long Achilles tendon and short muscle fibers, it ran at a speed of nearly 18 kilometers per hour, significantly faster than in simulations equipped with ape muscles, when it did not even reach a speed of 6.5 kilometers per hour. In simulations with human muscles, it also expended less energy.
However, even in simulations where the muscles were human, Australopithecus still ran much slower than modern humans, who can reach speeds of over 28 kilometers per hour. This result held true even when the researchers took into account Lucy's body size, which was significantly smaller than ours.
"This tells us that the body structure of A. afarensis significantly limits its running speed, compared to that of a modern human," Bates said.
Separate evolutionary path
Australopithecines walked more or less like humans – we know this from their skeletal structure, and also from the footprints they left behind, which have been preserved to this day. But running is a different matter, and the study shows that Lucy could not run like us. The researchers conclude that our running ability evolved separately, and later, from walking on two legs – it was not simply a “side effect” of it.
“Running speed itself has ecological significance,” said Australian archaeologist Amy Mosig Way, who was not involved in the study. “It’s one of the things that determines ecological success, for example the ability of an animal to escape predators or catch prey.” The new study, Way added, “shows that there is a specific evolutionary pathway for modern human running ability, separate from the one that led to walking.” Those of our ancestors who ran faster were more likely to survive and produce offspring that would carry that trait on to future generations. So over the past millions of years, both our skeletons and muscles have evolved to allow us to run faster and more efficiently.
More of the topic in Hayadan:
One response
Even among modern humans, leg length (i.e. stride length) is the most significant factor in running speed and efficiency, with the difference in the speed of movement of the runners' legs – number of steps/time – being minimal.
Australopithecus afarensis (up to 160 cm tall) had no chance in the competition.