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Robert J. Asher Headshot

Republicans and the Unsung Fossils (Starting With 'A')

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"Intelligent design" is not particularly newsworthy in 2012, except for the fact that it, along with climate skepticism and peculiar views on human reproduction, seems popular among some conservatives. In both 2008 and 2012, several Republican candidates felt they had to scoff at Darwin to have a shot at the nomination. My first reaction to this trend is one of dismay, tinged with hope, as the most successful, scientifically-informed policies of recent history include Nixon's Clean Air Act, Reagan's Montreal Protocol, and George H.W. Bush's cap & trade fight against acid rain. The anti-science of the far right is clearly not representative of the party, at least not historically. This doesn't make the legislative power of individuals within the House majority any less depressing, but it does serve as a crude introduction to my real topic: fossils. No, not the biological ideas of Todd Akin, but the biology preserved in the Earth's sedimentary rocks, which demonstrate just how wrong "intelligent design" supporters are when they claim that fossils do not support common descent, or the idea that organisms alive today evolved from shared ancestors.

Consider this quote from the 2007 "Intelligent Design" textbook Explore Evolution: "In the overwhelming majority of cases, common descent does not match the evidence of the fossil record." This book makes a case that biodiversity results from a kind of "design" incompatible with evolution by natural selection. Among other things, its authors allege that "missing links" are the rare exceptions to what is really a random jumble of petrified bones and teeth, manipulated by "evolutionists" to fit their (our) preconceptions.

To appreciate why this claim is wrong, consider what we would expect to find if species alive today really did evolve from organisms in the geological past, using the same biological processes present in living animals and plants. For starters, we should find animals in the fossil record that exhibit some but not all of the key attributes of their modern descendants. We would also expect fossils to occur in a sequence that broadly corresponds with the Tree of Life, with more ancestral species found in older rocks, with the important qualification that fossilization and speciation need not perfectly correspond.

Note that we do not expect to find "missing links" directly between two modern species (a misunderstanding epitomized by Kirk Cameron's crocoduck), but rather between the shared common ancestor and each of those modern species. Furthermore, the rate at which any given descendant accumulates novel features may vary a lot. An observation of stability across geological time (or "stasis") for one species is irrelevant to another that shows change. If you think paleontological stasis is a problem for evolution, go to Stephen Jay Gould's last book and look up his index entry for "creationism, errors about punctuated equilibrium and..."

So let's consider some fossils and ask if they bear out these expectations, starting with the "A"s. Everyone's heard of Archaeopteryx, the fossil bird that along with its wings and feathers (and unlike any living bird), has teeth, a tail, and a lizard-like pelvis. It is not a forgery, and new specimens of this animal have been discovered rarely but regularly since 1860, demonstrating a mix of anatomical features one would expect to find in an evolutionary lineage leading to modern birds.

A few years back Ardipithecus made a splash as a five-ish million-year-old member of our own lineage, predating species of Australopithecus like anamensis, afarensis, and africanus. These fossil hominins have a variety of adaptations in the skeleton showing an increasing reliance on bipedalism, for example a hip bone oriented back-to-front rather than side-to-side, and an opening in the skull for the spinal cord that is directed more downward than backward. They also possessed much smaller brains than modern humans, showing that our bipedalism evolved piecemeal, before our big heads. Even within specific body parts, our hominin relatives mixed features found in different species today, such as this australopithecine foot skeleton from South Africa that had an opposable big toe (like a chimp) alongside a very robust upper ankle bone, or "astragalus" (like a human).

Speaking of ankles and A's, Artiocetus is a 47 million-year-old whale which shows not only weight-bearing hindlimbs, but also exactly the kind of astragalus you'd expect to see in an animal that evolved from an ancestor shared with artiodactyls, along with antelopes and addaxes. Long before whales evolved from land-based ancestors, Acanthostega was a 365 million-year-old cousin of animals that move with muscular limbs and digits -- like amphibians, reptiles, and mammals -- sharing with them certain bones of the arm (humerus, radius, and ulna), but with an excess of digits.

The list of fossils goes on: Adapis, Aetiocetus, Algeripithecus, Amphisteum, Andescynodon, Apateon, Apheliscus, Apternodus, Archaeothyris, Asiatherium, Asioryctes... All of these fossils represent animals that Charles Darwin predicted would exist, but didn't know about when he wrote Origin of Species. They represent the past life from which we and other species alive today have descended, without the same complement of features present in the modern groups to which they're related.

Thanks to the theory of evolution, we know why many fossil "birds" had teeth and why fossil "mammals" still had their ear bones connected to their jaws as adults: because the features typical of modern birds and mammals did not evolve simultaneously. We know why Australopithecus didn't have eight fingers and why Archaeopteryx lacked steel claws: because these fossils shared genetic and developmental mechanisms with their descendants alive today. We understand why Acanthostega, Archaeothyris, Andescynodon, Asioryctes, Algeripithecus, and Australopithecus are found in precisely this temporal order: each represents successively more nested groups of animals, connected by genealogical descent over the course of geological time.

Paleontology is one of many lines of evidence that support Darwin's view of biological evolution. Denying this is just as absurd as claiming that the moon is made of cheese or that "legitimate rape" does not result in pregnancy. Most of our lawmakers agree with this, and I hope that someday all of them will be more eager to embrace science than creationism. They might even remember that at least one of our founding fathers enjoyed paleontology as a hobby, and learn about our extinct relatives starting with any letter of the alphabet.