In <em>Science and Human Origins</em>, Casey Luskin Reveals the "Big Bang" of Human Evolution - Evolution News & Views

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In Science and Human Origins, Casey Luskin Reveals the "Big Bang" of Human Evolution

Science and Human OriginsThe story of life's evolutionary history reflects a combination of etiology and teleology. Events unfold, linked in part by a chain of cause and effect. This is the etiological side of the story. But the narrative is incomprehensible if you don't also recognize the teleological side. This is the lesson of Casey Luskin's excellent chapter "Human Origins and the Fossil Record" in the new book from Discovery Institute Press, Science and Human Origins.

If you try to grasp the logic of this history from an exclusively etiological perspective, you'll be left puzzled by illogical gaps, sudden inexplicable developments, jumps and leaps, evolutions and revolutions that seem to defy all sense: in biological terms, saltations. Things fall into place only when you understand that even as the story is being pushed ahead from behind, in ordinary historical fashion, simultaneously it is being pulled and drawn forward according to a purposeful design, from somewhere unknown up ahead.

Luskin's chapter is in some ways the centerpiece of Science and Human Origins. His subject is paleoanthropology and the mystery of the "Big Bang" in human evolution, a term that aptly describes the emergence of our genus Homo some two million years ago, preceded by ape-like australopithecine predecessors that may or may not be our ancestors.

It's a Cambrian explosion writ small, encompassed by what may even be a single species. As Luskin points out, other "species" in the genus Homo are "so similar to us that some paleoanthropologists have classified erectus and neanderthalensis as members of our own species, Homo sapiens." Probably, they could successfully breed with us. Cleaned up and appropriately dressed, they could walk our streets without attracting much notice.

The picture of human evolution we get from popular media and low-level textbooks -- a smooth gradient leading from ape-like creatures to man -- is a false one. Luskin has done the hard work of gathering for a non-specialist readership what the specialists in the subject actually say. In fact, he writes, "the fossil evidence for human evolution remains fragmentary, hard to decipher, and hotly debated."

Debated, that is, among professional paleoanthropologists. Luskin quotes an article in the journal Science pointing to the "pitifully small array of bones" used "to construct man's evolutionary history....One anthropologist has compared the task to that of reconstructing the plot of War and Peace with 13 randomly selected pages."

"Pitiful" is the right word to describe the physical remains on which so much about our self-understanding as human beings hangs in the balance. One supposed human ancestor, Ardipithecus ramidus, a/k/a Ardi, the "Oldest Skeleton of Human Ancestor Found" (National Geographic), is known from a skull that was "crushed to 4 centimeters in height," her skeleton similarly "crushed nearly to smithereens," seemingly "trampled down into mud by hippos and other passing herbivores."

Even if Ardi's frame could be reliably reconstructed, primatologists like Esteban Sarmiento find "no evidence that Ardi is on the human lineage. Those characteristics that [the creature's discoverer Tim White] posited as relating exclusively to humans also exist in apes and ape fossils that we consider not be in the human lineage."

Later examples of our allegedly immediate ancestors, the australopithecines, are plagued by the same kinds of problems. Their most famous representative, Lucy, is a relatively impressive fragment. Some 40 percent of her skeleton survives -- if it is the skeleton of one individual, which is unclear. Also uncertain is how Lucy got around, whether in human or ape-like fashion. The latter seems more likely. There's good reason to doubt she was bipedal. Part of the difficulty, again, resides in poor preservation. Her pelvis, a key piece of evidence, was "badly crushed" when it was found.

University College (London) paleoanthropologist Leslie Aiello summarizes: "Australopithecines are like apes, and the Homo group are like humans. Something major occurred when Homo evolved, and it was not just in the brain." Luskin rightly emphasizes the abruptness of this appearance, the form of man emerging from no identifiable lineage.

Casey Luskin is telling a story that was already told by anthropologists, though the media and scientists themselves, when they speak for public consumption, labor to obscure this. The break, the saltation, comes at about the 2 mya (million years ago) mark, a "period of very rapid evolution" characterized by swelling brain size and sweeping physiological reengineering. Even Ernst Mayr, a leading figure in evolutionary biology, conceded that, "The earliest fossils of Homo, Homo rudolfensis, and Homo erectus, are separated from Australopithecus by a large, unbridged gap."

The rest of evolutionary history, of course, similarly weaves together etiological and teleological development, where long periods of mellow stasis are suddenly interrupted by the crash of lightning, precipitating bursts of what appears to be intelligent design. The story of man reveals this pattern of stasis and explosion in a particular dramatic way, laden with emotion and significance that cannot be matched by any other chapter in the narrative of life.

Somehow, meanwhile, these bursts of creativity have to be explained away if the Darwinian idea is to be maintained. And so we find that explaining away has become more or less the full time job of most evolutionary biologists.