Evolutionists also refer to comparative anatomy. But again, these do not tell us how the species arose. Similarity between species does not imply an evolutionary relationship. In fact, comparative anatomy commonly reveals contradictory patterns. Distant species share the same designs, and sister species show very different designs.
Evolutionists also refer to small-scale adaptation we can observe. But we don’t know that these adaptations generally accumulate to create large scale change evolution requires. In fact even evolutionists have agreed this is doubtful, and that some other, unknown, mechanism is required. In fact, these adaptations are produced as a consequence of profoundly complicated molecular structures and mechanisms, whose origin evolution does not explain.
Is there evidence for evolution? Sure, there is plenty of evidence for evolution. But there are significant problems with evolution. There is plenty of evidence for evolution just as there is plenty of evidence for geocentrism. But the science does not bode well for either theory.
So the evidence for evolution follows this general pattern: Even at its best, it does not prove evolution to be a fact. And furthermore, the evidence reveals substantial problems with evolution.
So how can evolutionists proclaim evolution to be a fact with such fervor? There seems to be a glaring mismatch between the evidence and the truth claims of evolutionists. The answer is that evolutionists use contrastive reasoning. Evolution is not claimed to be a fact based on how well it fits the evidence, but rather on how poorly the alternative fits the evidence. Evolution is proved by the process of elimination.
For example, evolutionists explain that nature’s apparently useless or harmful designs make no sense except on evolution. Such harmful designs are actually not predicted by evolution. They are low probability on evolution, but such harmful designs are at least understandable given evolution’s lack of planning. The designs may be low probability, but not altogether impossible.
But if the species were intelligently designed, then these useless or harmful designs make no sense. So we might say that evolution is proved not by positive evidences, but by negative evidences. And in fact the worse the evidence, the better for evolution, because such negative evidences are even worse for the alternative.
Indeed, there are no demonstrations of the fact of evolution that do not appeal to such contrastive reasoning. Evolutionists have a great many proofs for the fact of evolution, but they always entail some form of this contrastive reasoning. Here is how philosopher Eliott Sober explains contrastive reasoning:
This last result provides a reminder of how important the contrastive framework is for evaluating evidence. It seems to offend against common sense to say that E is stronger evidence for the common-ancestry hypothesis the lower the value is of [the probability of E given the common-ancestry hypothesis]. This seems tantamount to saying that the evidence better supports a hypothesis the more miraculous the evidence would be if the hypothesis were true. Have we entered a Lewis Carroll world in which down is up? No, the point is that, in the models we have examined, the ratio [the probability of E given the common-ancestry hypothesis divided by the probability of E given the separate-ancestry hypothesis] goes up as [the probability of E given the common-ancestry hypothesis] goes down. … When the likelihoods of the two hypotheses are linked in this way, it is a point in favor of the common-ancestry hypothesis that it says that the evidence is very improbable. [Evidence and Evolution, p. 314]
These evolutionary arguments and conclusions are very powerful. It seems that the evolutionist’s argument is compelling. The species must have arisen spontaneously via evolutionary mechanisms. But in all of this there is a catch.
Science cannot know all the alternative explanations for the origin of the species. When evolutionists conclude evolution is a fact via the process of elimination, they are making a subtle but crucial non scientific assumption—that they know all the alternative explanations.
So all of these powerful evolutionary arguments for the fact of evolution are non scientific. In other words, evolution has extremely powerful and compelling arguments, but the cost of building such a powerful case is that the idea is not scientific.
Without these powerful proofs, evolution would lie exposed to the many scientific problems and contradictions. The idea that the world, and all of biology, spontaneously arose is, from a strictly scientific perspective, extremely unlikely. But evolution is shielded from such problems by its powerful non scientific proofs.
This non scientific aspect of evolution is immense and would be difficult to underestimate. It has dramatically altered the very perception of science and its evidence. For given the fact of evolution, all of biology is interpreted according to the idea. The many scientific problems with evolution become more friendly “research problems.” And the theory becomes immune to scientific skepticism.