Evolution of the Knuckle Head
An evolutionary anthropologist looked at the knuckles of chimpanzees. Then she looked at the knuckles of gorillas. Then she looked at her own knuckles. Conclusion: humans evolved from tree climbers, not knuckle walkers. Her theory can be read in Live Science, based on a paper in PNAS.1
Tracy Kivell and Daniel Schmitt from Duke University admitted up front, “Despite decades of debate, it remains unclear whether human bipedalism evolved from a terrestrial knuckle-walking ancestor or from a more generalized, arboreal ape ancestor.” Apparently those who think neither answer is correct were not part of the debate. Those who think science should stick to evidence might notice this operative line in the Live Science article: “There are no fossils from the time of this transition, which likely occurred about seven million years ago, Kivell and Schmitt said.” Whatever evidence there is for their hypothesis in the absence of fossils, it surely seems open to slippery interpretations, as evidenced from this quote from their paper:
The results of this study show that researchers need to reevaluate all posited knuckle-walking features and reconsider their efficacy as indicators of knuckle-walking behavior in extant and extinct primates. In this context, the absence of several posited knuckle-walking features in extant knuckle-walkers (and the presence of some of these features in nonknuckle-walkers) makes it difficult to argue that there is unambiguous evidence that bipedalism evolved from a terrestrial knuckle-walking ancestor. Instead, our data support the opposite notion, that features of the hand and wrist found in the human fossil record that have traditionally been treated as indicators of knucklewalking behavior are in fact evidence of arboreality and not terrestriality….
Our data cannot reject the hypothesis that knuckle-walking evolved only once at the base of the African ape and human clade and that these differences evolved after the Gorilla and Pan [chimpanzee] split (Fig. S1). Without fully understanding the evolutionary and ontogenetic plasticity of these osteological features or the affect on wrist morphology of other locomotor behaviors in which Pan and Gorilla engage, it is difficult to be certain about the evolution of nonhomologous knuckle-walking behavior in African apes. However, in absence of clear evidence for a terrestrial knucklewalking origin for human bipedalism, we suggest that the independent evolution of a generalized locomotor adaptation that simply allows large-bodied apes to retain highly-arboreal morphology while also moving effectively on the ground is a reasonable and likely evolutionary scenario.
It seems clear that evidence is no longer required for the National Academy to publish a suggestion. Whether others allowed in the debate will find their suggestion reasonable and likely remains to be seen. Ironically, in Nature this week,2 Jonathan Marks (U of North Carolina at Charlotte) wrote a letter arguing that “Ape and human similarities can be deceptive.” Some features can be “overenthusiastically interpreted,” he said, that are “not directly homologous.” He was talking about behavioral studies, but then he said it can also apply to comparisons of feet: “They are similar, and are descended from a common ancestral structure, but they are by no means the same.”
But then Marks revealed something that shows that opposite interpretations can be used as support for Darwin. He said that one can argue differences instead of similarities and still be a loyal Darwinian – maybe a better one:
A genuine Darwinian approach to primate behaviour may have to acknowledge that the brains of apes (and their capabilities) may simply be different from our own, like their feet. Evolution, after all, is the production of difference. If one scholar acknowledges the adaptive divergence that has occurred between a human and a chimp over 7 million years or so of separation, and another insists that they are the same, then who is really in denial of evolution?
Is it even possible to deny evolution if that is the game plan? Opposite evidence and opposite interpretations can both be used to show one is a good Darwinian. How can a Darwin skeptic even get a foothold in the debate?3
1. Tracy Kivell and Daniel Schmitt, “Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor,” Proceedings of the National Academy of Sciences, August 10, 2009, doi: 10.1073/pnas.0901280106.
2. Jonathan Marks, “Ape and human similarities can be deceptive,” Nature460, 796 (13 August 2009) | doi:10.1038/460796a.
3. Maybe only by pointing out that a theory that can be argued with opposite evidence and opposite interpretations is not a scientific theory at all – it can explain anything, therefore explains nothing.
What a sad state of affairs when any dumb idea can get published by the National Academy and then given a favorable review by popular science reporters. You thought the thing that differentiated science from other speculations was the demand for evidence. That, sad to say, is long gone. Now, you just have to belong to the “in” crowd (i.e., those who have not been Expelled). Then you can put forward any suggestion you want as long as it never questions the totalitarian dictator of the world, Charles DearOne.
The word “evolution” and its cognates appear 26 times in their paper, never once questioned or supported by evidence: e.g., “Since Darwin first discussed pathways of human evolution in The Descent of Man, there has been an ongoing and often rancorous debate over the nature of locomotion in our prebipedal human ancestor.” This debate is never about whether humans evolved from apes, but just how. Well, how many decades or centuries do they get to debate among themselves before the referee calls the game? That’s all this is, anyway: just a game. None of them cares about the truth. They just want job security in the regime of the Dear One.
These people are completely clueless about how silly they look to the rest of us. If they knew, they would run off into the trees with heads low, like knuckle-walkers. Those with logic in their brains (those who haven’t knuckled under the regime’s requirement to become a knucklehead, e.g., those who argue that looking at current knuckles of living primates says nothing about human evolution without begging the question), remain camped outside with the other well-dressed, scholarly Visigoths, waiting for the right time to liberate the captives. It shouldn’t take much longer. The insiders are all drunk on Darwine.