If you love predictability, you’ve got to love the Discovery Institute. Whenever someone publishes a paper about human evolution, it’s a pretty safe bet that someone there will soon take the time to explain how having learned something new means that we somehow know less than we did before. You can set your watch by it, almost.
The latest example comes from Casey Luskin. He “discusses” a paper that came out in Nature this week that reported on some fossils from Dmanisi, Georgia. Several skulls have been described from this site already, and the current paper focuses on post-cranial (less technically, non-skull) remains.
I’m not going to bother with a detailed, point-by-point rebuttal of Casey’s claims. (See this post by Afarensis for that.) Instead, I’m just going to look at one of the more glaringly dishonest tactics that Casey used this time.
In his post, Casey discusses some of the information he got from a figure in the text:
According to the Figure 3 in the Nature report, the femoral length is like that of a human or a gorilla (Fig. 3b). The tibial mediolateral distal width is like that of a chimp, human, or bonobo. Figure 3a reports that the tibia length is quite similar to that of a gorilla but different from that of humans. (Figure 3 also reports the length of an arm bone, as the humeral length resembles that of a human or perhaps a chimp (Fig. 3b).) Finally, the fossil footbones that were discovered are reported have some features that are like human feet, and others that are closer to the feet of modern apes.
Casey’s description of the information is accurate without being in any way an honest depiction of what the figure actually reports. Casey, you see, is discussing each axis of the graphs independently – first, he talks about femoral length, then about tibial width, then tibial length, and so on. It’s no surprise that he finds that the fossil resembles humans in some respects and various apes in others. If you were to violate a recent grave, grab some bones, and repeat the analysis, you’d reach similar conclusions. The normal range for femoral length in humans is very similar to the normal range in gorillas; the normal range of humeral length for humans overlaps with the normal range in chimps and orangutans.
The authors of the paper reported the bone lengths for the fossil because they were looking at how those dimensions relate to each other. Their approach, unlike Casey’s, makes sense. Humans have a very distinctive arm-to-leg ratio compared with the other great apes. Here’s what part of the figure Casey was mining actually looks like. Figure 3b:
Legend: Stars, Dmanisi Homo; X, AL288-1 (Australopithecus afarensis); diamond, BOU-VP-12/1; triangle, KNM-WT15000 (H. erectus); Z, recent Homo sapiens; plus signs, Pan troglodytes; Y, Gorilla gorilla; squares, Pongo pygmaeus. (Legend and figure from Lordkipanidze, D. et al., 2007)
Looking at the figure, it seems that the picture isn’t exactly as ambiguous as Casey was trying to pretend. Yes, you can say that the femoral length of the fossil falls within the normal range for both humans and gorillas. Yes, you can say that the length of the fossil falls within the normal range for both humans and chimps. Yes, saying both of those things without bothering to mention what the figure actually shows is dishonest.
Casey then turns around and uses his oh-so-careful interpretation of the graph to reach this conclusion about the fossils:
For those claiming this is clearly a species evolving into humans, a few troubling facts emerge from these data: This species lived millions of years after the supposed split in the lines that led to apes, and humans, respectively. I cannot be faulted for hoping that if there is an evolutionary story to be told here, this fossil would tell me whether it was evolving towards a modern ape, or a modern human. Yet these leg and foot bones in many respects resemble modern apes as much as they resemble modern humans. I cannot be faulted for being skeptical of the claim that these species were necessarily evolving towards modern humans. Is it possible these scientists are anthropomorphizing this find by assuming that it’s evolving towards humanity?
Actually, Casey, you can be faulted for that claim. In fact, you should be. Not only have you taken some of the bone size data from the paper out of context to support your claim, you’ve also conveniently forgotten to mention a number of other pertinent facts. You didn’t mention that this species had a very human-like arm-to-leg length ratio. You didn’t mention that the fossils clearly show that the species walked upright. You didn’t mention that there are skulls that are associated with the bones discussed in this paper, and that the skulls were analyzed in a separate paper. You didn’t mention that some of the animal bones found at this site show tool marks, demonstrating that this species used tools to remove meat from the animals. I could go on, but the sheer tonnage of the things that you failed to mention in your efforts to obfuscate this paper is getting to be a bit much.
Lordkipanidze, D. et al. 2007. Postcranial evidence from early Homo from Dmanisi, Georgia. Nature. Vol 449, pp305-310.