A regular letter contributor to this page recently argued that evolutionary theory is wrong because, among other things, “No one has ever seen or documented macro-evolution such as a dog giving birth to a cat or a reptile to a bird” (Daily News, Feb. 17). I agree with this statement. If we did observe such an event, evolutionary biologists would need to go back to the drawing board. Further, this statement tells us that the writer simply does not understand evolutionary theory and given the long history of similar statements from this individual, we can only assume that willful ignorance is his modus operandi in such matters (including the topic of climate change).
Macroevolution concerns differences that distinguish higher levels of taxonomic division (e.g., genus, family, order, etc.). In the example given by the reader, cats and dogs share a common ancestor from the time that the kingdom Animalia emerged, through the separation of the phylum Chordata from others to the class Mammalia, and to the order Carnivora. But the shared common ancestry for cats and dogs separated at the level of family (Felidae and Canidae, respectively).
Consequently, even in your wildest nightmare, the idea that a dog would beget a cat is completely absurd. In the fullness of time, and given sufficient genetic variation, selection pressure, genetic isolation, etc., a descendent lineage of dogs might come to resemble domestic cats in shape and size, but it would not be a member of Felidae. That boat left the harbor a long time ago.
Our writer also claims that there are no transitional fossils. Transitional fossils have traits that are common to both ancestral and descendent groups of organisms. There are many examples of such fossils and simply denying this fact isn’t a useful argument. My personal favorite is the Tiktaalik roseae, which was first discovered in 2004 and harkens to an era 375 million years ago. This critter shares features of fish (e.g., gills, scales, and fins) and traits of land animals (e.g., a mobile neck and strong ribcage). It is my favorite because the team that discovered this fossil hypothesized that such a transitional fossil could be found in river deposits from the Late Devonian Epoch. That is, based on thorough study and understanding of the paleontological record, they predicted where such a fossil would be found, and they got lucky enough to find it.
Speaking of luck, our writer shares the “just-so” idea that the solar system is “precisely designed” and therefore a product of an intelligent power. The just-so method of reasoning is not only flawed, but ironic given the long history of acrimony in biology over the use of just-so stories to explain why specific traits evolved. As Eliabeth Lloyd (2015) summarized, this is the difference between asking “what is the function of this trait?” instead of “does this trait have a function?” Put another way, our writer concludes that the function of the solar system is to support life on earth while ignoring the simpler conclusion that we got lucky to have conditions suitable for life to emerge.
The proposition of design requires magical thinking and an all-powerful deity, while chance only requires a lottery ticket. It might seem far-fetched to think that such conditions can be found by chance, until you consider that there are an estimated 200 billion trillion stars in the universe, and over 70 quintillion planets (and these estimates predate the launch of the Webb telescope). As of late 2019 there were 4,099 exoplanets cataloged by astronomers, of which about 55 are found in what we call the habitable zone of stars. Based on this ratio there could be 50 billion such planets in our galaxy alone. I really do appreciate our cosmic luck as much as the next person, but in the final analysis, ours is a pretty pedestrian solar system.
We still don’t know how life itself emerged, but there is some exciting work on the idea that self-replicating RNA molecules were involved. We’ll see how that goes but given the history of science and the advancement of technology, I’m pretty optimistic that the god of the gaps will continue to shrink in the decades to come.
Call (he/him) is a microbiologist and father of three. He first discovered the Palouse 38 years ago.
