In contrast, the Ardipithecus niche was comprehensively revealed in ∼250 published pages of a single issue of Science in 2009 ( 8). Broader aspects of Australopithecus paleobiology emerged gradually during the 20th century. The new fossils disrupt such frameworks.Īrdipithecus is a primate that ruptures several deeply held perceptions, particularly those visualizing humans as “just a third species of chimpanzee” ( 7). Furthermore, because Australopithecus is often found in open environments, hominid origins are frequently presented as the tale of a tropical forest ape forced to adapt to open savannas that expanded via global climate change. Today “conventional wisdom” continues to reflect the deeply held assumption that Australopithecus is close to some imagined chimpanzee-like Miocene ape species. Many assumed that when pre- afarensis fossils were eventually recovered they would increasingly resemble chimpanzees. Rather, it represents an adaptive plateau occupied for ∼3 Ma by up to four species lineages of small-brained African bipeds. afarensis seems very much like a missing link between the living African apes and later hominins in its dental, cranial, and skeletal morphology” ( 6).Īustralopithecus can no longer be legitimately viewed as a short-lived transition between apes and humans. Indeed, a widely used textbook still proclaims that, “Overall, Au. Thus, despite a host of unique specializations to committed terrestrial bipedality, many declared this species “.very close to what can be called a ‘missing link’” ( 5). The preoccupation with chimpanzee comparisons led many to argue that Lucy and her conspecifics walked like apes, without human-like hip and knee extension. However, without our current appreciation of the power of regulatory mechanisms, faith in simple DNA similarity also helped reify the notion that chimpanzees were appropriate primitive proxies for hominid ancestors ( 4).ĭuring the 1970s Australopithecus afarensis discoveries pushed knowledge back to 3.7 million years ago (Ma), but even the iconic “Lucy” differed little from already known South African fossils. The data ultimately resolved the phylogenetic branching order among extant great apes and humans. In the 1960s molecular data challenged notions that species lineages of modern apes and humans could be traced directly to early and middle Miocene fossils. Australopithecus comprised different species of small-brained but bipedal Pliocene primates. Both were rejected as hominids by eminent authorities, but two grades of human evolution were eventually recognized. Homo erectus was found in the 1890s, and Australopithecus in the 1920s. It easily fit the fossil record of his day, when only a few Neanderthals were known. These fossils have begun to rectify the mistaken notion that contemporary apes, in particular common chimpanzees, can serve as adequate representations of the ancestral past.ĭarwin's human evolution scenario attempted to explain hominid tool use, bipedality, enlarged brains, and reduced canine teeth ( 2). However, they substantially reveal the early evolution of the hominid clade (the term “hominid” denoting all species on the human side of the human/chimpanzee phylogenetic split). These paleontological discoveries do not yet include the common ancestor we shared with chimpanzees (the CLCA). Now, however, long sought and recently discovered African fossils provide escape from such persistent but inaccurate projection. The notion that modern great apes are little changed from the last common ancestors we shared with them promoted the assumption that hominid fossils anatomically intermediate between living apes and ourselves would eventually be found. Nevertheless, Darwin and his less cautious contemporaries and intellectual descendants used humans and modern apes to triangulate ancestral anatomy and behaviors, which promulgated the erroneous metaphor of a hominid “missing link.” Even today, despite thousands of available fossils, this deeply embedded metaphor reinforces the misconceptions that extant apes-particularly chimpanzees-can be viewed as “living missing links,” or that that modern African apes combined can be used to represent the past “as time machines” ( 3).
“.the stock whence two or more species have sprung, need in no respect be intermediate between those species.”Ĭharles Darwin famously suggested that Africa was humanity’s most probable birth continent, but warned that without fossils, it was “…useless to speculate on this subject” ( 2).
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