But because we walk upright on the ground and no longer climb, we have lost some of the specializations that characterize other apes. Some anatomical features of the torso and arms in modern humans attest to our ape-like heritage.
Chimpanzees and gorillas use a special form of locomotion on the ground called “knuckle-walking.” Humans, by contrast, walk upright. Gibbons, siamangs, orangutans, gorillas and chimpanzees have arms longer than their legs their wide torsos facilitate extended reach of limbs, and their short lower backs stabilize their upright torsos. This kind of climbing is present in all living apes except humans. “Suspensory climbing,” which is practiced with an upright body posture and the grasping of multiple branches by multiple limbs, allows apes to grow larger in size while still remaining agile high up in the trees. “Hominoids,” or what we commonly call the apes, are distinguished from monkeys by a suite of anatomical features well designed for a special kind of arboreal locomotion. The gorilla lineage split from the common hominin and chimp lineage before these latter two separated somewhat later.Īnthropologists have tended to envision very early hominins as rather “ape-like,” resembling modern chimps and gorillas. DNA data demonstrates that gorillas are slightly more genetically distant from humans than are chimps. This lack of evidence was exacerbated by the absence of a known fossil record for chimpanzee and gorilla ancestors. Knowledge of human evolutionary history prior to australopithecines has, therefore, remained extremely limited indeed, half of hominin evolutionary history was largely unknown. However, because these remains are fragmentary, their status is open to debate. Over the past decade, new fossil evidence has moved this divergence back to 7 million years or more, following the discovery of what are purported to be very early hominins, Orrorin tugenensis and Sahelanthropus tchadensis. Using “molecular clock” rates of genetic change standard among primates and other mammals, scientists have calculated that the chimpanzee and human lineages diverged as early as 6 mya. Analysis of DNA has indicated that modern humans and modern chimpanzees are closely linked in evolutionary history, and share approximately 98 percent of their genetic material. Until now, our knowledge of the hominin fossil record had been extremely meager before about 3.7 (mya), the age of the earliest known australopithecine remains. She takes her place among the pantheon of fossil hominin individuals, including Lucy ( Australopithecus afarensis), the Taung child ( Australopithecus africanus), and the Nariokatome boy ( Homo erectus), that illustrate important steps in hominin evolution.įigure 1. Ardi is represented by a skull and teeth, as well as the pelvis, hands, and feet. The most complete individual, an adult female, has been nicknamed “Ardi.” She is estimated to have been 120 centimeters (4 feet) tall and to have weighed 50 kilograms (110 pounds).
Together, these represent a minimum of 36 individuals.
Over the next year, additional discoveries were made, ultimately totaling more than 100 fossilized bone specimens, many quite fragmentary. A report of these finds was published in the journal Nature in 1994. The initial discovery was made in 1992, consisting of several teeth and a jaw. They have been classified under the taxonomic designation Ardipithecus ramidus. The fossils, dating to 4.4 million years ago (mya), were discovered in the Afar Rift region of Ethiopia by a research team lead by Professor Tim White of the University of California at Berkeley. It is certainly fitting that in the year we celebrate the 200th anniversary of Charles Darwin’s birth and the 150th anniversary of the publication of his monumental work On the Origin of Species, a major advance in our understanding of human evolution should be announced.Īfter 15 years of painstaking study by 47 researchers, the journal Science has devoted its October 2 issue to reports, 11 papers in all, on the fossilized remains of what is interpreted to be an early form of hominin, the group including humans and all human ancestors back to the evolutionary split with the last common ancestor with chimpanzees.
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