(An hour* to kill, so let’s muddy the water on, as Dr. Xavier says, Eeeevolution!)
So, we last left the topic of evolution by means of natural selection as described by Dawkins in his Summa The Selfish Gene and in his follow up The Extended Phenotype with a couple of bald assertions:
1. The key intellectual assertion underlying Darwin’s Origin of Species is the claim that tiny pressures can, if consistently applied over long enough time, result in substantial, material change. I’ll add here the critical lemma: these changes may appear as if they could only arise by conscious design, but that is an illusion.
2. A key idea implicit in The Selfish Gene is that selection pressure doesn’t need to be applied to every individual in every generation to have an effect, allowing for the possibility that traits might be selected for that promote survival in the face of comparatively rare yet sufficiently recurring ‘pressures’.
To expand: Darwin was famously influenced by the geological uniformitarianism of Lyell and Hutton. (BTW: People who come up with 10 dollar words like uniformitarianism should be taken out and shot. How about calling it the Same Laws Assumption? Two fewer syllables, clear, easy words. That, I suppose, would be too pedestrian for big-time science guys. But I digress…). Tiny, generally imperceptible geologic events can result, over time, in the Alps or the Grand Canyon. And so, the seemingly tiny yet controversial step: same thing applies to living creatures.
Problem: uniformitarianism tacitly assumes that mountains today are like all mountains at all times, at least within the time frames considered at the time – the idea of starting with congealing discs of gas and rubble and ending up with the Grand Tetons by applying one consistent set of natural laws didn’t figure into it, at first, as far as I know. Instead, Hutton looked at geological activity going on today in familiar classes of things – rivers, mountains, canyons – and speculated that the same processes, applied consistently and long enough, result in the forms we see today. His controversial conclusion: the world had to be very old, much older that the 6,000 years many people believed.
Hutton didn’t need to concern himself with really ancient geology, the kind that gets you from 4.5 billion years ago to, say, 500 million years ago, a geology of cometary accretion and planetary collisions. His thoughts work just as well in a sort of steady state world where mountains, rivers, and canyons always existed and, presumably, might always continue to exist. It is a more modern generalization of the same principles to apply uniformitarianism to galactic time frames and star formation leading to planet formation leading to geology that ends up with the Andes and heads towards black holes and heat death.
But life is not like ageless mountains. At least superficially, living creatures today are quite different from creatures 10 million years ago, very different from living creatures 100 million years ago, and vastly different from living creatures a billion years ago. Darwin could see that these differences required him to describe a mechanism that had a) uniform laws; yet b) “improved” in some sense the “product”. Hutton could assume that mountains 10 million years ago were fundamentally the same as mountains today; fossil evidence meant Darwin could see that animals today were not like the forms of long ago. He, himself, was aware that evolutionary change did not necessarily mean better, just better adapted to the current environment. At the same time, the idea that natural selection creates “better” forms as time goes on, while philosophically inconsistent within a materialistic universe, is an idea that won’t die. Is slime mold inferior to people? Why? How? Even setting aside the metaphysical issues raised by the concept of ‘better’, compared to slime mold, we people are evolutionary ephemera.
What I’m getting at with all this: while uniformitarianism in geology generates layers of rock quite a lot like the layers of rocks 10 or 100 or 1,000 million years ago, uniformitarianism in biology creates flower mimicking mantises from single-cell anaerobic bacteria in similar amounts of time.
A conglomerate rock can carry within it pebbles of conglomerate rock, which pebbles themselves might be made up of conglomerate pebbles. This could be seen as uniformitarianism building up new forms from older forms, as the current forms are only possible because the same uniformitarianism has built the older forms. One could say these new rocks are better or more sophisticated or at least more advanced than than the old rocks, but only a dogmatic materialist would say that those rocks are sophisticated or advanced in the same way as redwoods and manatees are advanced, that behaviors like those of parasitic barnacles are really of the same class as the ‘ behaviors’ of rocks.
While conglomerates of conglomerates of conglomerates do, in some sense, contain a history of uniformatarianism in action, those flower mantises mentioned above contain a history more potent. They carry within them descendents of the genes carried by those anaerobic bacteria – genes whose existence strongly suggests they are not only advantageous (or, at least not too disadvantageous) to the mantis today, but were advantageous to survival of single-cell organisms in an anaerobic environment, and every environment in between.
Perhaps the form, and certainly the expression, of such descendent genes has changed over the past couple billion years, so that whatever survival purposes they may have served for the bacteria are no longer relevant or even present in the mantises. But two things have happened along the way:
– Those genes were selected for or against over and over and over again. Maybe they freeloaded along for generations, in the changing organisms they found themselves in, maybe they were repurosed continually, perhaps they once in a while proved useful, even very useful. But to think they would survive for a couple billion years without ever conferring some advantage on some level at least once in a while to the billions of creatures that have carried them is all but a refutation of uniformitarianism – it would be like finding a billion copies of Mexican Hat, and having to defend how they each came about as the individual, unrelated operation of wind and rain over time.
(aside: There’s what might be called a visual bias to evolutionary discussions – we note and build our examples upon striking, visible attributes of striking, visible organisms. Yet, just as most life is microscopic, most natural selection takes place at what might be called the level of metabolism. Once read that the difference between marsupials and placental mammals boils down to placental mammals extracting energy from their food a percent or two more efficiently than kangaroos and platypuses. This allows for more activity per unit intake, or more energy-demanding physical features (such as bigger brains). Over time, a 1% difference in survival rates tends to be utterly decisive. Therefore, if the advantage in metabolism translates to even a 1% difference in survival rates, it can be expected to dominate. Since marsupials and placental mammals tend to occupy the same sorts of niches, wherever they compete, you’d expect placental mammals to out-survive the marsupials. All this evolutionary competition springs from the invisible workings of the differentiated digestive tracts of animals.
And that’s *still* at a higher level than where most evolution takes place – even more basic functions, functions that have been around for 2 billion years, have been subject to selection and refinement over all that time. The battles that go on in your bloodstream every second, where invaders are tagged and targeted for destruction be special ops troops, and fight back with stealth and deception, who commandeer the cellular production facilities for their own nefarious purposes – that’s where the action is, and is the result of a multi-billion year arms race across constantly changing terrain. It’s the context in which to understand the truth that, whether the lion eats the antelope or not, 99% of the genes ‘win’. All the stuff going on amidst sophisticated multi-cellular creatures, all that hunting and evading and reproducing, can perhaps be most accurately seen as the microscopic arms race being fought by our genes’ mech warriors. Al least, from an evolutionary perspective.)
– Over such a range of time, rare events become common, so to speak. We know, for example, of plants and fungi which require a forest fire in order to grow and reproduce. Yet any one piece of forest might go decades between fires. Locusts can go generations living as relatively benign grasshoppers, before something – as yet unknown – triggers their conversion into swarms – a behavior presumed to have been selected for, even though most individual locusts never swarm. But what about even rarer events? In the previous post, we talked about fish being washed into dark caves, and then, generations later, being washed out, and different breeding populations of the same species getting mixed after a long separation. Who knows what the threshold for the frequency with which an event has to happen before it becomes ‘selected for’, so to speak? Such frequency would be different, no doubt, depending on the type of event and type of species. The same event – say, the drying up of a lake or an ice age – might eliminate any number of species and yet provide an opportunity for a subset of some others. The genes that helped the winners survive one such occurrence might survive many generations until the next such occurrence, where they might help promote survival yet again. With enough repetitions occurring frequently enough, perhaps the genes that promote survival in such situations might ‘stick’ (a topic for another post).
And it’s not like any one species is subject to only kind of semi-rare event. Rather, all species around today are the products of a couple billion years of selection, which presumably includes untold millions of semi-rare selection events.
All this is to say that, logically, we need to consider natural selection as occurring not merely between individuals in one generation in a relatively steady-state environment, but also as occurring whenever any event happens in which some individuals die and others survive. We should expect that any general response to such recurring but infrequent events represent adaptation. Thus, when cichlids speciate to fill many niches in a newly formed lake within a few centuries, that is an adaptation – little vigorous fish have found virgin lakes millions of times over the eons, and those that filled the niches fast and well held on to them long, and left many offspring. Cichlids, in other words, have evolved to evolve.
* Ha! Make that hours and hours in 15 – 30 minute chunks over a week. I get what I think is a quick little idea, and end up writing a small novella on it….