Human Origins, and the Real Reasons for Evolutionary Skepticism
Chapter 8: What About Us?
In Chapter 8, Coyne turns his attention to human evolution. He lists examples of alleged human-chimpanzee intermediates, including Sahelanthropus tchadensis, Orrorin tugenensis, and Australopithecus africanus.
An interesting paper published in PNAS by Collard and Wood (2000) criticized phylogenetic inference based solely on cranial and dental evidence. The authors report,
Cladistic analysis of cranial and dental evidence has been widely used to generate phylogenetic hypotheses about humans and their fossil relatives. However, the reliability of these hypotheses has never been subjected to external validation. To rectify this, we applied internal methods to equivalent evidence from two groups of extant higher primates for whom reliable molecular phylogenies are available, the hominoids and papionins. We found that the phylogenetic hypotheses based on the craniodental data were incompatible with the molecular phylogenies for the groups. Given the robustness of the molecular phylogenies, these results indicate that little confidence can be placed in phylogenies generated solely from higher primate craniodental evidence. The corollary of this is that existing phylogenetic hypotheses about human evolution are unlikely to be reliable.Is Sahelanthropus tchadensis a genuine intermediate linking humans and chimps? A 2002 news report on the BBC website, reporting on the find, noted,
"I tend towards thinking this is the skull of a female gorilla," Dr Senut said. "The characteristics taken to conclude that this new skull is a hominid are sexual characteristics.Wolpoff et al. (2002), writing in Nature, also observe that there are "many...features that link the specimen with chimpanzees, gorillas or both, to the exclusion of hominids." Moreover, they note, "Sahelanthropus does not appear to have been an obligate biped."
"Moreover, other characteristics such as the occipital crest (the back of the neck where the neck muscles attach)... remind me much more of the gorilla," she said, saying older gorillas also had these characteristics.
The evidence of bipedality in Orrorin tugenensis is flimsy as well. An article featured in National Geographic in 2006 noted,
Terry Harrison, a biological anthropologist of the Center for the Study of Human Origins at New York University, studies hominins that predated O. tugenensis during the Miocene, 23.8 to 5.3 million years ago.The most famous australopithecine is Lucy. But Collard and Aiello (2000) argue on the basis of Lucy's hand-bones that she "knuckle-walked." Moreover, they consider much of Lucy's body to be "quite ape-like" with "relatively long and curved fingers, relatively long arms, and funnel-shaped chest."
While he praised Richmond's thorough analysis, he believes that a comparison of O. tugenensis with older Miocene hominids could reveal that it's actually more like those older species -- and was thus tree-dwelling.
"It does not make sense [to] interpret the anatomical features of O. tugenensis as a biped that could climb trees," he said.
"I see it as a good arboreal quadruped that has a package of features like [those found in] Australopithecus."
There is also the problem of the large unbridged gap between Australopithecus afarensis and Homo erectus. Given the very small window of time separating the two species, could the evolutionary mechanism plausibly accomplish the sheer number of instances of anatomical novelty that are required to change an Australopithecus afarensis into a Homo erectus (see Varki and Altheide, 2012, for a catalogue)? It seems to me that it could not. Indeed, according to Durrett and Schmidt (2007, 2008), a waiting time of six million years is required for the occurrence and fixation of a single mutation in a nucleotide-binding site, and a waiting time of 216 million years is required for the binding site to gain two mutations (assuming that the first is neutral).
For more detailed discussion of this subject, see Science and Human Origins, published by Discovery Institute Press.
What can we conclude about the evidence, as Jerry Coyne puts it, that "evolution is true"? The arguments for common ancestry presented in his book are, at best, inconclusive. Although some of his arguments are stronger than others, Coyne fails to address the numerous counterarguments against common descent. Moreover, Coyne fails to impart confidence in the causal adequacy of the selection/mutation/drift mechanism. Even if common ancestry is true (which it could well be), that does not necessarily entail the validity of the proposed neo-Darwinian mechanisms as the central processes driving macroevolutionary change.
In the final chapter of his book ("Evolution Redux"), Coyne attempts to psychoanalyze critics of evolution, speculating about the "real reason" for evolution-skepticism, which he thinks is religious commitment. Ironically, however, it is the materialist, and not the theist, who is committed to an evolutionary account of life's origins. The theist has more options open. This commitment was aptly stated by Harvard evolutionary biologist Richard Lewontin who admitted to being forced to "accept a material explanation of the phenomenal world" not by "the methods and institutions of science" but by "a prior commitment, a commitment to materialism." Like Coyne, many evolutionary theorists refuse to accept that there are people who are just as intelligent and educated as they are yet who disagree with them.
For many of us critics of Darwinian evolutionary theory, the problem is not a theological qualm about neo-Darwinism, but rather our observation that the claims of modern evolutionary theory do not comport with the evidence. Coyne's book leaves our doubts as they were, squarely in place.