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Love for Lucy
February 9, 2009Posted by on
I don’t know why I do it to myself. Perhaps I’m a glutton for punishment and frustration. Every so often, I’ll feel the need to go to one of those Intelligent Design/Creationism blogs and get myself all angry and riled up. This morning I went over to Evolution News and Views and saw that Casey Luskin has been to the Pacific Science Center’s Lucy exhibit, and he’s soooooo not impressed. That’s okay though, because I’m not impressed with his critique.
The first thing my friends and I noticed when seeing Lucy’s bones was the incompleteness of her skeleton. Only 40% was found, and a significant percentage of the known bones are rib fragments. Very little useful material from Lucy’s skull was recovered. (This seems to be common: many of the replica skulls of early hominids at the exhibit were clearly based upon extremely fragmentary pieces.) And yet, Lucy still represents the most complete known hominid skeleton to date.
I’m not sure if this is just a confusion of terms or just glaring ignorance, but Lucy is not the most complete fossil hominid known to date. Meet Nariokotome Boy. If you’re looking for complete skulls, let me introduce you to the Taung Child, Little Foot, Mrs. Ples, or KNM-ER 406. Or, open a book and introduce yourself to any number of the other skeletons that are comparatively or more complete than Lucy.
Next, he says:
If the next rainstorm could wash Lucy away completely, what happened during the prior rainstorms to mix-up “Lucy” with who-knows-what? How do we know that “Lucy” doesn’t represent bones from multiple individuals or even multiple species?
Well, you see, a person doesn’t get to be a paleontologist unless she knows her anatomy. She has to know where every single little muscle attaches onto every single little bone. It’s her job. All of this anatomical knowledge makes it really easy when someone comes into a forensic anthropologist and says, “I think I’ve found a human skeleton behind my house, and I suspect murder!” A forensic anthropologist can go to that site, look at a single bone fragment from the tibia or a medial phalanx and tell the person, “No, don’t worry, this is just a dog.” She can do this because she is intimately familiar with anatomy, and knows how, in the dog, the tibial plateau will be shaped quite differently than in the human because of the different mechanical requirements.
Paleoanthropologists can do the same thing with Lucy’s pelvis or femur. The pelvis and femur don’t look like anything we see in any quadrupedal animal at all. And wow- that COMPLETE sacrum is just screaming “BIPEDAL ANIMAL HERE!!!” We can look at muscle attachment sites and say, “Gee, whoever this was, she had a really huge gluteus minimus!” We can then compare the size of different gluteus minimus muscles across the animal kingdom and see that only animals who walk upright have such a large gluteus minimus. So, it’s not merely that we’ve counted up our bones and we don’t have any duplicates. We can look at the functional anatomy of these bones and determine that we don’t have a quadruped.
Regardless, seeing the broken scraps of old Lucy laid out under the protective glass, with full skeletal and full-flesh reconstructions of Lucy abounding throughout the exhibit, I could not help but recall the words of the famed physical anthropologist Earnest A. Hooton, who in 1931 wisely counseled that “alleged restorations of ancient types of man have very little, if any, scientific value and are likely only to mislead the public.” (Up From The Ape, pg. 329.)
It’s important to note the date that Earnet A. Hooton said this. It was 1931. That was before we had anything to base our restorations on! Of course restorations in 1931 were misleading and unscientific. That didn’t stop the very same Earnest Hooton from concluding that black babies were closer to primitive man than white babies, though, so take his wise counsel with a grain of salt.
Luskin then talks about how the Lucy’s curved phalanges, long arms, and funnel-shaped chest detract from Lucy’s position as a transitional hominin:
Lucy did have a small, chimp-like head, but as Mark Collard and Leslie Aiello observe in Nature, much of the rest of the body of Lucy’s species, Australopithecus afarensis, was also “quite ape-like” with respect to its “relatively long and curved fingers, relatively long arms, and funnel-shaped chest.”
Collard and Aiello’s article also reports that we now have “good evidence” that A. afarensis (including Lucy) “‘knuckle-walked’, as chimps and gorillas do today.”
First, a nit to pick: Of course A. afarensis was “quite ape-like.” It’s an ape! Humans are also “quite ape-like” with respect to our Y-5 molar pattern. Our opposable thumbs are rather monkey-like. Our five digits are rather tetrapod-like. Our digestive system is rather deuterosome-like. The nucleus in our cell is rather eukaryote-like. And the fact that we have DNA is rather prokaryote-like. Hopefully you see where I’m going with this, but just in case you don’t- “ape-like” doesn’t mean, “resembling modern apes.” It means “resembling the primitive ape-like condition.”
Okay, now let’s look at this evidence for knuckle-walking. It includes a tiny ridge on one of the metacarpals that indicates a wrist-locking mechanism. Now let’s look at that sacrum again. It’s completely restructured, and unlike any quadruped we know. Why is Luskin so quick to accept a tiny ridge on a carpal bone, and so willing to throw out the sacrum completely? Is it because the carpals reinforce your preconceptions, while the sacrum blatantly flies in their face?
Further on, Luskin is feeling generous:
Let’s assume for the moment that Lucy was a fully bipedal ape: should that necessarily qualify her as a human ancestor? Given that the much earlier fossil record from the Miocene yields bipedal apes that supposedly evolved upright-walking completely independently from the line that supposedly led to humans, it would seem that the answer is clearly no.
That Miocene ape he’s talking about isn’t Oreopithecus, is it? I can only conjecture, since he won’t come right out and say who he’s talking about, but a bipedal construction of Oreopithecus is based on some horribly deformed lumbar vertebrae. Again, we have a case of someone latching onto a fringe interpretation because it supports his preconceptions.
Okay, how ’bout this:
It doesn’t seem very advantageous, and therefore likely, to use bipedality as your primary mode of locomotion if you can’t use it to quickly run away from predators.
And what if, instead of running away from them on flat Earth, you were retreating to trees to get away from them? Wouldn’t we then expect not only adaptations for bipedalism, such as a wide sacrum and a short ilium, but also adaptations for arboreal life, such as curved phalanges and long arms? Let’s go back to our friends, the knuckle-walkers. Knuckle-walkers only knuckle-walk when they’re on the ground foraging. When they’re in the trees, they swing. No one would look at a chimp skeleton and say, “Oh, they were knuckle-walkers, so how could they get into a tree?” The two aren’t mutually exclusive. And depending on the amount of swinging A. afarensis was doing, bipedalism and climbing trees aren’t mutually exclusive, either. In fact, it’s just what you would expect from a creature that was “transitioning” from an exclusively arboreal existence to an exclusively terrestrial one, don’t you think?
Further, we know that Australopiths lived in forests. Forest animals are not known for their speed, but for their agility. Being a short, wide-hipped animal isn’t good for speed, but it is pretty good for agility. Humans didn’t evolve for speed until they left the forests.
Luskin then throws around some old quotes from 1995 and 1981 to show that we need more fossils. Well, guess what? We’ve found more! Each one of them makes our perception of human evolution a little clearer, but you know what? We still need more! Does this mean that paleoanthropology is a dead science? Of course not! It means that it’s a healthy, growing science that it still in its childhood, if not its infancy! So yes, we should all take Luskin’s advice and “keep an open mind” about Lucy and our origins. But we should also let the evidence shape our conclusions instead of forcing it into something it’s not.