By David MacMillan.
4. Transitional fossils.
One of the most common and most frustrating creationist objections to evolution is the claim that there are no “missing links” or “transitional fossils” required by evolution. This claim is made without qualification, particularly in presentations to lay or church audiences. As unthinkable as it might seem, creationists really do believe that transitional fossils simply do not exist. On this basis, they conclude that evolution must be false.
They maintain this completely erroneous view by consistently misrepresenting what a transitional fossil actually is. Creationists don’t deny that Archaeopteryx, Pakicetus, Tiktaalik, Australopithecus, and similar prominent examples of transitional fossils exist; they rather argue that these are not “true” transitional fossils.
The last section dealt with misconceptions about evolution on the population level: the “where” of evolutionary change. This installment will focus on misconceptions about how evolutionary change happens over time. Evolution is properly understood as “descent with modification”, where the critical word is “descent”. The life on earth today is not the same as the life which was once on earth, the life we descended from. As this series has already illustrated, creationists do not dispute the concept of change; rather, they dispute the concept of descent in the way it is described by the theory of evolution.
Young-earth creationists believe that all life, living and fossil, can be grouped into a series of families – they call them baramins, a made-up Hebrew word for “created kinds” – which all existed together at the same time from the very beginning. They use this completely artificial understanding of our planet’s biosphere in generating their concept of a “missing link”: in order for something to be a “true” transitional form under their model, it would have to be something halfway between two separate created “kinds”. Because they automatically assign every species to a particular created kind and only to that created kind, their “transitional form” is something that could never exist.
The usual parodies of evolutionary transitional fossils, like Ray Comfort’s infamous crocoduck, are openly tongue-in-cheek. But because creationists see all animals as belonging to individual, immutable kinds, they represent evolution as “change from one ‘kind’ to another” claiming that evolution predicts we should see transitions between their “created kinds”: for example, a fossil that is midway between a dog and a cat. Just as with living species, all fossil species are placed within strict “created kinds”, allowing creationists to maintain the illusion that nothing is ever “in-between”.
This characterization is a complete misunderstanding of what evolution actually predicts. No one expects one existing species to evolve into another. The “kinds” alleged by creationism simply do not exist in the evolutionary model; there is no line between one family and another that a transitional form needs to straddle.
What creationists don’t recognize is that the theory of evolution does not predict “transitional” fossils at all – at least, not in the way creationists expect. Evolutionary theory does not predict that there will be “normal” fossils most of the time, while chimaera-like “transitional” fossils will appear tucked in-between. Evolution has no general prediction about a unique class of transitional fossils. Instead, evolution makes predictions about the specific morphology, age, and location of the individual fossils it expects to discover. It bases these individual predictions on other specific fossils that have already been discovered.When morphology and a variety of other factors indicate that one particular species is the distant ancestor of another particular species, evolutionary principles can be used to predict the attributes of one or more intermediate species.
These predictions can be directly employed to make new discoveries; Tiktaalik, the transitional form between lobe-finned fish and all tetrapods, was found in the exact region in the exact range of strata that evolution had predicted it would be found. Adding to the confusion, creationists also erroneously assume that in order for a species to be truly intermediate, it must contain parts that are only partly functional – half-working lungs in fish, half-formed wings in theropod dinosaurs, and so forth. This assumption is another misunderstanding about evolutionary descent. In order for a new trait to become fixed in a population in the first place, the trait must be maximally adapted to the environment. Evolution thus does not predict functionless or half-functioning intermediate organs and morphologies, but rather organs which are fully optimized to their environment but are repurposed by a later organism as part of a different design. For example, the human appendix is evidence for evolution not because it is functionless (it does, in fact, have a function), but because it was adapted from the cecum, which provided a different function to our ancestors. All life is full of little bits and pieces showing how evolution has adapted different structures for different purposes in its universal descent. Yet to creationists, none of this is “true” evidence for evolution, because they imagine that “true” evolution would produce functionless structures. Functionless structures, of course, are the one thing evolution cannot manufacture.
In applying this belief, creationists invariably move the goalposts. Any hypothetical function, no matter how minor or speculative, is taken to mean that the morphology in question couldn’t have been transitional. Even if they can’t think of a function, they’ll still hold out that there could be a function, and so it’s not proven to be transitional – all while completely misunderstanding what a transitional form really is.
These two objections – that a given fossil isn’t “really” transitional because it’s “not in-between two kinds” or because all its organs are fully functioning – are recycled over and over every time a new intermediate fossil is discovered. Even when a new species is discovered exactly matching a specific evolutionary prediction, it is still discounted using these two objections. Alternatively, creationists announce that the new species is a new “kind” and then point out the two spaces on either side of it as further “missing links”. In their eyes, every new link means there are twice as many holes to fill.
Sometimes this misconception can be dismantled by inquiring exactly what sort of transitional fossils the creationist thinks evolution expects. “Describe the specific attributes of a fossil which you would consider evidence for evolutionary common descent.” The creationist will either fail to come up with anything (demonstrating that his model is set up to explain away all evidence, no matter how obvious), or will describe something that evolution would not predict in the first place.