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Australopithecines and Retroactive Confessions of Ignorance

Casey Luskin
human origins
Photo: An artist imagines Australopithecus afarensis, Hall of Human Origins, Smithsonian National Museum of Natural History; reconstruction by John Gurche; photographed by Tim Evanson / CC BY-SA.

Editor’s note: We are delighted to present a series by geologist Casey Luskin asking, “Do Fossils Demonstrate Human Evolution?” This is the third post in the series, which is adapted from the recent book, The Comprehensive Guide to Science and FaithFind the full series here.

Many paleoanthropologists believe that the later hominins called australopithecines were upright-walking and ancestral to our genus Homo. Dig into the details, however, and ask basic questions like Who?, Where?, and When?, and there is much controversy. As one paper noted, “there is little consensus on which species of Australopithecus is the closest to Homo,”1 if any. Even the origin of genus Australopithecus itself is unclear.

Retroactive Confessions of Ignorance

In 2006, National Geographic ran a story titled “Fossil Find Is Missing Link in Human Evolution, Scientists Say,”2 reporting the discovery of what the Associated Press called “the most complete chain of human evolution so far.”3 The fossils, belonging to species Australopithecus anamensis, were said to link Ardipithecus to its supposed australopithecine descendants. 

What exactly was found? According to the technical paper, the claims were based upon canine teeth of intermediate “masticatory robusticity.”4 If a few teeth of intermediate size and shape make “the most complete chain of human evolution so far,” then the evidence for human evolution must be indeed quite modest.

Besides learning to distrust media hype, there is another lesson here. Accompanying the praise of this “missing link” were retroactive confessions of ignorance. That’s where evolutionists acknowledge a severe gap in their model only after thinking they have found evidence to plug that gap. Thus, the technical paper reporting these teeth admitted, “Until recently, the origins of Australopithecus were obscured by a sparse fossil record” and noted, “The origin of Australopithecus, the genus widely interpreted as ancestral to Homo, is a central problem in human evolutionary studies.”5

Evolutionists who retroactively confess ignorance risk that the evidence that supposedly filled the gap may not prove very convincing. This seems to be the case here, where a couple of teeth were all that stood between an unsolved “central problem in human evolutionary studies” — the origin of australopithecines — and “the most complete chain of human evolution so far.” Moreover, we’re left with admissions that the origin of australopithecines is “obscured.”

Australopithecines Are like Apes

While early hominins are controversial due to their fragmentary remains, there are sufficient known australopithecine specimens to generally understand their morphology. Australopithecus, which literally means “southern ape,” is a genus of extinct hominins that lived in Africa from about 4.5 to 1.2 million years ago. “Splitters” (paleoanthropologists who infer many different species) and “lumpers” (those who see fewer) have created a variety of taxonomic schemes for the australopithecines. The four most commonly accepted species are afarensisafricanusrobustus, and boiseiRobustus and boisei are larger-boned and more “robust,” and are sometimes classified within the genus Paranthropus.6 They are thought to represent a later-living offshoot that went extinct without leaving any living descendants. The smaller “gracile” forms, afarensis and africanus, probably lived earlier, and are classified within the genus Australopithecus.

The best-known australopithecine fossil is Lucy (which belonged to afarensis), one of the most complete known fossils among pre-Homo hominins. She is often described as a bipedal ape-like creature that is an ideal precursor to humans. Yet only 40 percent of Lucy’s bones were found, with a large percentage being rib fragments. Very little useful material from Lucy’s skull was recovered, and yet she is one of the most significant specimens ever found. Bernard Wood refutes the misapprehension that she resembled some ape-human hybrid: “Australopithecines are often wrongly thought to have had a mosaic of modern human and modern ape features, or, worse, are regarded as a group of ‘failed’ humans. Australopithecines were neither of these.”7

Others have questioned whether Lucy walked like humans or was significantly bipedal. An article in Natureobserved that much of her body was “ape-like,” especially with respect to the “relatively long and curved fingers, relatively long arms, and funnel-shaped chest.”8 It further reported “good evidence” from Lucy’s hand-bones that her species “‘knuckle-walked,’ as chimps and gorillas do.”9 A New Scientist article adds that Lucy appears well-adapted for climbing, since “Everything about her skeleton, from fingertips to toes, suggests that Lucy and her sisters retain several traits that would be very suitable for climbing in trees.”10 Richard Leakey and Roger Lewin argue that A. afarensis and other australopithecines “almost certainly were not adapted to a striding gait and running, as humans are.”11 They recount paleontologist Peter Schmid’s striking surprise upon realizing Lucy’s nonhuman qualities: “What you see in Australopithecus is not what you’d want in an efficient bipedal running animal.”12

As for Lucy’s pelvis, many claim it indicates bipedal locomotion, but Johanson and his team reported it was “badly crushed” with “distortion” and “cracking” when first discovered.13 These problems led one paper to propose Lucy’s pelvis appears “different from other australopithecines and so close to the human condition” due to “error in the reconstruction…creating a very ‘human-like’ sacral plane.”14 Another paper concluded that a lack of clear fossil data prevents paleoanthropologists from making firm conclusions about Lucy’s mode of locomotion: “The available data at present are open to widely different interpretations.”15

More Differences from Humans

Other studies confirm australopithecine differences from humans, and similarities with apes. Their inner ear canals — responsible for balance and related to locomotion — are different from Homo but similar to great apes.16 Traits like their ape-like developmental patterns17 and ape-like ability for prehensile grasping by their toes18 led a Nature reviewer to say that “ecologically they [australopithecines] may still be considered as apes.”19 Another analysis in Nature found the australopithecine skeleton shows “a mosaic of features unique to themselves and features bearing some resemblances to those of the orangutan,” and concluded that “the possibility that any of the australopithecines is a direct part of human ancestry recedes.”20 A 2007 paper reported “[g]orilla-like anatomy on Australopithecus afarensis mandibles,” which was “unexpected,” and “cast[s] doubt on the role of Au. afarensis as a modern human ancestor.”21

Paleoanthropologist Leslie Aiello states that when it comes to locomotion, “[a]ustralopithecines are like apes, and the Homo group are like humans. Something major occurred when Homo evolved, and it wasn’t just in the brain.”22 The “something major” was the abrupt appearance of the human-like body plan — without direct evolutionary precursors in the fossil record. 

Next, “The Human Fossil Record Lacks Intermediaries.”


  1. Henry McHenry and Katherine Coffing, “Australopithecus to Homo: Transformations in Body and Mind,” Annual Review of Anthropology 29 (2000), 125-146.
  2. John Roach, “Fossil Find Is Missing Link in Human Evolution, Scientists Say,” National Geographic News (April 13, 2006), (accessed October 26, 2020).
  3. Seth Borenstein, “Fossil Discovery Fills Gap in Human Evolution,” NBC News (April 12, 2006), (accessed October 26, 2020). 
  4. See Tim White et al., “Asa Issie, Aramis, and the Origin of Australopithecus,” Nature 440 (April 13, 2006), 883-889.
  5. White et al., “Asa Issie, Aramis, and the Origin of Australopithecus.”
  6. Bernard Wood, “Evolution of the Australopithecines,” The Cambridge Encyclopedia of Human Evolution, eds. Steve Jones, Robert Martin, and David Pilbeam (Cambridge, UK: Cambridge University Press, 1992), 231-240.
  7. Wood, “Evolution of the Australopithecines.”
  8. Mark Collard and Leslie Aiello, “From Forelimbs to Two Legs,” Nature 404 (March 23, 2000), 339-340.
  9. Collard and Aiello, “From Forelimbs to Two Legs.” See also Brian Richmond and David Strait, “Evidence That Humans Evolved from a Knuckle-Walking Ancestor,” Nature 404 (March 23, 2000), 382-385.
  10. Jeremy Cherfas, “Trees Have Made Man Upright,” New Scientist 97 (January 20, 1983), 172-177.
  11. Richard Leakey and Roger Lewin, Origins Reconsidered: In Search of What Makes Us Human (New York: Anchor, 1993), 195.
  12. Leakey and Lewin, Origins Reconsidered, 193-194.
  13. Donald Johanson et al., “Morphology of the Pliocene Partial Hominid Skeleton (A.L. 288-1) From the Hadar Formation, Ethiopia,” American Journal of Physical Anthropology 57 (1982), 403-451.
  14. François Marchal, “A New Morphometric Analysis of the Hominid Pelvic Bone,” Journal of Human Evolution 38 (March 2000), 347-365.
  15. M.M. Abitbol, “Lateral View of Australopithecus afarensis: Primitive Aspects of Bipedal Positional Behavior in the Earliest Hominids,” Journal of Human Evolution 28 (March 1995), 211-229 (internal citations removed).
  16. Fred Spoor et al., “Implications of Early Hominid Labyrinthine Morphology for Evolution of Human Bipedal Locomotion,” Nature 369 (June 23, 1994), 645-648.
  17. Timothy Bromage and M. Christopher Dean, “Re-Evaluation of the Age at Death of Immature Fossil Hominids,” Nature 317 (October 10, 1985), 525-527.
  18. Ronald Clarke and Phillip Tobias, “Sterkfontein Member 2 Foot Bones of the Oldest South African Hominid,” Science 269 (July 28, 1995), 521-524.
  19. Peter Andrews, “Ecological Apes and Ancestors,” Nature 376 (August 17, 1995), 555-556.
  20. C.E. Oxnard, “The Place of the Australopithecines in Human Evolution: Grounds for Doubt?” Nature 258 (December 4, 1975), 389-395.
  21. Yoel Rak, Avishag Ginzburg, and Eli Geffen, “Gorilla-Like Anatomy on Australopithecus afarensis Mandibles Suggests Au. afarensis Link to Robust Australopiths,” Proceedings of the National Academy of Sciences 104 (April 17, 2007), 6568-6572.
  22. Leslie Aiello, quoted in Leakey and Lewin, Origins Reconsidered: In Search of What Makes Us Human, 196. See also Bernard Wood and Mark Collard, “The Human Genus,” Science 284 (April 2, 1999), 65-71.