Timescale of ævolution. Previously, I wrote about how plain old somatic cells spend most of their time in stationary phase. This got me to thinking about evolution, and how our everyday experiences give rise to a great lack of intuition of the rate of change in biological systems. This lack of intuition has particular relevance to the origin-of-life question.

I'll illustrate this as plainly as possible: first, consider any random animal that you see fairly often. If you're a land mammal (and I know I am), then you're most familiar with other species that, like you, don't live in the ocean, and are large enough you can actually see them. And because of this, chances are that the animal you think of probably doesn't reproduce until at least one year of age (or maybe even older if you thought of larger animals like us). I'll posit that the average generation lifetime on land is roughly ~1 year. Something on that order, at least.

But let's imagine that you were around for the early days soon after life arose. Minimalist, single-celled creatures swim about, budding off daughter cells every so often. If we assume that these singly celled creatures reproduced at roughly the same rate as fresh-water bacteria do now, roughly once every 100 hours, then we're already talking about genetic drift ocurring with incredibly higher frequency than land mammals. In this scenario, the single-celled organisms' generation lifetime is 87 times faster than the land mammals'.

87 means that for every kiddo one land animal brings forth, the first bacterium now will have 2⁸⁷ - 1 ≈ 1.5×10²⁶ daughter cells. That's enough bacterial mass to outweigh all the concrete in the Three Gorges Dam (the largest concrete structure in the world). In this one year alone, the bacteria would have tested approximately 10¹⁹ mutations, enough to mutate their entire genome 5×10¹² times over. The human, on the other hand produces one new offspring with about 175 mutations. Those mutations amount to about a billionth of one percent of its genome.

Yes, most mammals today speciate at a much slower rate than when life first arose. But this is because single-celled organisms vastly outdo larger animals in their ability to try out new solutions. They are so much better at it, and so much faster at it, that it just makes sense that all the common cellular machinery could have been perfected by them long before multi-celled species arose. (Lo, and behold, that we all share the same basic machinery, from E. coli all the way to H. sapiens!)

The larger animals' genomes have also had plenty of time to stabilize to current environmental pressures. In other words, if they're already well-matched to their environment, mutating provides no new advantage. In stable systems, things just tend not to spontaneously leave equilibrium states.

There are many misunderstandings about the feasibility of natural selection as a speciation mechanism. But there's not much missing in the big-picture model itself. Those who shun the natural world in favor of their traditions must be lacking in themselves an appreciation for the beauty of the natural world.

Surely God would not be too happy about that.