Editor’s note: This post recalls a conversation I previously had with a creationist. In this conversation I used the example of the Bengal Tiger which I took Aron Ra’s Falsifying Phylogeny video series, along with some of the other ideas described here.
In a conversation with a creationist family member, I was asked to present the best evidence for evolution. I mentioned that we had discovered legged whales and egg laying mammals as the theory would suggest. He questioned the authenticity of these (though they are very real) and did not find arguments concerning their existence convincing. I went another route and argued from the point of phylogeny.
Simply put, living things do not exists as some sort of continuum of distinct non over-lapping kinds, as one would expect if all living things were specially created in their present form. Instead, we have a hierarchy of kinds within kinds, as is indicative of a branching off process such as evolution. For example, the Bengal Tiger is undeniably a subspecies of tiger, all of which are a variety of panther, all of which are varieties of cat. All cats of course are feliforms (cat like mammals), which are a variety of carnivore (members of the order Carnivora, not all of which are meat eating), all of which are placental mammals. All placental mammals are mammals (as are monotremes and marsupials), and all mammals are Synapsids. All synapsids are amniotes, which in turn are all tetrapods and all tetrapods are vertebrates, which in turn are all chordates and so it goes.
Any known living thing can be placed into a similar hierarchy of kinds within kinds, all of which are based on upon shared characteristics at each level. These characteristics are not arbitrary and many levels of distinction are obvious (for example the fact that geese and falcons are both birds was recognized long before the development of taxonomy). In fact, modern taxonomy was developed in pre-Darwinian times by a Christian Creationist. The fact that such, taxonomic cladograms are possible indicates that the worlds life forms diversified through a process of branching off into different lineages.
This is not to say that a common designer could not have designed all lifeforms in this way (a supernatural designer could presumably create things however he or she wants, which is why intelligent design has no predictive value), but it would seem that such a designer would either be using an evolutionary process or intentionally creating things to appear as if they were created through such a process. It also gives us a place where evolution if, false, could be easily disproved. All one would have to do is find something that does not and cannot fit into the existing phylogeny of the worlds living thing. Most of the creatures of mythology count, including Pegasus. griffins, mermaids, and centaurs. This not to mention all the other possible chimeras one could think up, like birds with dragon fly wings or the conventional depiction of angels as winged humans with feathers.
This at the very least gave my creationist relative pause, which I think was a good start at getting the conversation moving.