Given that all five of our special senses are built around cilia, how might we think about this fact from a teleological perspective? Well, all I can say is that this fits quite well within two primary themes that I have been fleshing out over the last couple of years.
First, if we wanted to front-load evolution such that the sense of sight and hearing are more likely to emerge when metazoan-type life emerges, then we would expect cilia to be quite ancient. And in fact they are – they are as old as eukaryotes themselves. In fact, the last common ancestor of all eukaryotes not only had cilia (or flagella), but probably had the complex system for ciliogenesis (a process known as intraflagellar transport).
Of course, I have long known about the ancient state of cilia, so let’s push it some more. Let us propose the original core function of cilia has always been sensory. In other words, while most people think of cilia as motility structures, this may be more of a secondary function. If the original function for cilia has always been sensory, then “the business end” of our five senses have always been there from the start of eukaryote existence.
Second, I have also tried to get people to shift their perspective and stop taking basic biological facts for granted. In the past, I have raised the possibility that evolution and natural selection have been as successful as they have because they are built around protein biochemistry. That is, without proteins, there is no reason to think the blind watchmaker would ever produce a biotic world analogous to ours. Extending on that theme, I have asked about the missing “prokaryotic mice” and have argued that evolution and natural selection would never have produced something akin to a mouse without the eukaryotic cell plan.
Both hypotheses are strongly disliked by non-teleologists, as they are metaphysically invested in the notion that all sorts of complex life forms, similar to complex life forms that exist today, could exist without proteins and/or the eukaryotic cell plan. In their minds, the only reason these alternative life forms do not exist is because the “right environment” was never at work and that is simply because of contingency. There is nothing special about proteins or the eukaryotic cell plan. While non-teleologists may dislike my hypotheses, they cannot show the hypotheses are wrong or unreasonable and have no evidence for thinking their “many roads to Rome” perspective is correct (and let’s not forget that this perspective misled biologists when it came to the discovery of deep homology). It simply boils down to metaphysical preference that is enforced with peer pressure.
So let’s continue to build. In the past, I have offered and supported the hypothesis that introns have facilitated the evolution of metazoan-type complexity and raised this as one of the reasons why the prokaryotic cell plan cannot generate a mouse-like creature. Now, let’s add another reason to the mix – cilia.
Cilia, as sensory devices built around the eukaryotic cytoskeletal plan, have likewise facilitated that evolution of metazoan-type complexity. And when we begin to entertain this hypothesis, it also begins to make a lot of sense why the eukaryotic flagellum looks so different from the prokaryotic versions.
These are themes I’ll be exploring in the future.