How Does An Animal That Is A Biped Move Around
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Welcome to Hominid Hunting's new series "Condign Human being," which will periodically examine the evolution of the major traits and behaviors that ascertain humans, such as big brains, language, technology and art. Today, we wait at the most central human feature: walking upright.
Walking upright on ii legs is the trait that defines the hominid lineage: Bipedalism separated the outset hominids from the residuum of the four-legged apes. It took a while for anthropologists to realize this. At the turn of the 20th century, scientists thought that large brains made hominids unique. This was a reasonable determination since the only known hominid fossils were of erudite species–Neanderthals and Homo erectus.
That thinking began to change in the 1920s when anatomist Raymond Dart discovered the skull known every bit the Taung Child in S Africa. Taung Child had a pocket-size brain, and many researchers thought the approximately three-million-year-old Taung was but an ape. But one feature stood out as being human-like. The foramen magnum, the hole through which the spinal cord leaves the caput, was positioned farther forrard under the skull than an ape'due south, indicating that Taung held its caput erect and therefore probable walked upright. In the 1930s and 1940s, further fossil discoveries of bipedal apes that predated Neanderthals and H. erectus (collectively called australopithecines) helped convince anthropologists that walking upright came before big brains in the evolution of humans. This was demonstrated most impressively in 1974 with the finding of Lucy, a most consummate australopithecine skeleton. Although Lucy was pocket-sized, she had the anatomy of a biped, including a wide pelvis and thigh bones that angled in toward the knees, which brings the feet in line with the torso's center of gravity and creates stability while walking.
In more than contempo decades, anthropologists take determined that bipedalism has very ancient roots. In 2001, a group of French paleoanthropologists unearthed the seven-million-year-old Sahelanthropus tchadensis in Chad. Known just from a skull and teeth, Sahelanthropus' status as an upright walker is based solely on the placement of its foramen magnum, and many anthropologists remain skeptical about the species' form of locomotion. In 2000, paleoanthropologists working in Republic of kenya found the teeth and 2 thigh bones of the six-million-year-sometime Orrorin tugenensis. The shape of the thigh basic confirms Orrorin was bipedal. The earliest hominid with the near extensive evidence for bipedalism is the iv.4-million-twelvemonth-old Ardipithecus ramidus. In 2009, researchers appear the results of more xv years of analysis of the species and introduced the world to a well-nigh complete skeleton called Ardi.
Although the earliest hominids were capable of upright walking, they probably didn't get around exactly as nosotros do today. They retained primitive features—such as long, curved fingers and toes too as longer artillery and shorter legs—that indicate they spent fourth dimension in trees. Information technology'southward not until the emergence of H. erectus 1.89 million years ago that hominids grew tall, evolved long legs and became completely terrestrial creatures.
While the timeline of the evolution of upright walking is well understood, why hominids took their first bipedal steps is non. In 1871, Charles Darwin offered an caption in his book The Descent of Homo: Hominids needed to walk on two legs to free up their easily. He wrote that "…the hands and arms could inappreciably have become perfect enough to take manufactured weapons, or to have hurled stones and spears with a true aim, as long as they were habitually used for locomotion." One problem with this idea is that the earliest stone tools don't testify up in the archaeological record until roughly ii.v million years ago, well-nigh 4.5 million years after bipedalism's origin.
Simply after the unveiling of Ardi in 2009, anthropologist C. Owen Lovejoy of Kent State University revived Darwin's caption by tying bipedalism to the origin of monogamy. I wrote about Lovejoy'south hypothesis for World magazine in 2010. Lovejoy begins by noting that Ardi's discoverers say the species lived in a wood. As climatic changes fabricated African forests more seasonal and variable environments, it would have become harder and more fourth dimension-consuming for individuals to find nutrient. This would have been peculiarly difficult for females raising offspring. At this point, Lovejoy suggests, a mutually benign organisation evolved: Males gathered food for females and their young and in render females mated exclusively with their providers. To be successful providers, males needed their arms and hands free to acquit nutrient, and thus bipedalism evolved. This scenario, equally with all bipedalism hypotheses, is really hard to test. But earlier this year, researchers offered some support when they plant that chimpanzees tend to walk bipedally when carrying rare or valuable foods.
Another theory considers the efficiency of upright walking. In the 1980s, Peter Rodman and Henry McHenry, both at the University of California, Davis, suggested that hominids evolved to walk upright in response to climate change. Every bit forests shrank, hominid ancestors found themselves descending from the trees to walk across stretches of grassland that separated wood patches. The most energetically efficient fashion to walk on the ground was bipedally, Rodman and McHenry argued. (Full disclosure: Rodman was my graduate school counselor.) In 2007, researchers studying chimpanzees on treadmills determined that the chimps required 75 percent more energy while walking than 2-legged humans, providing some evidence that bipedalism has advantages.
Numerous other explanations for bipedalism have been outright rejected, such as the thought that our ancestors needed to stand upward to see over tall grass or to minimize the amount of the body exposed to the sun in a treeless savannah. Both ideas were debunked by the fact that the first hominids lived in at to the lowest degree partially wooded habitats.
Although hard to study, the question of why bipedalism evolved might come up closer to an respond if paleoanthropologists dig up more fossils of the earliest hominids that lived seven 1000000 to 6 one thousand thousand years ago. Who knows how many species of bipedal apes they'll notice. But each new discovery has the potential to fundamentally change how nosotros understand the origins of one of our most distinctive traits.
Source: https://www.smithsonianmag.com/science-nature/becoming-human-the-evolution-of-walking-upright-13837658/
Posted by: batsonallind.blogspot.com
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