I was reading a book about sleep last week and I learnt something about birds: they can sleep with half of their brains. That’s already pretty weird, but what’s even stranger is a certain behaviour groups of birds perching on the same branch exhibit. If, say, there are ten birds lined up on the same branch resting, the central eight will fall asleep fully. The ones on the outside will fall asleep with half of their brains, keeping their “outer” ears and eyes fully awake to keep watch for danger. It’s as if they’ve been given the role of night watchmen, but of course, this isn’t a coordinated effort. As much as birds are demonstrably intelligent in certain ways, they haven’t quite evolved to the point of delegating tasks to each other. In a way I think that makes it all the more impressive – this behaviour is something that natural selection has produced entirely by chance in its neverending system of proliferating genes that help organisms survive.
In the same vein, I decided to track down a couple of other examples of natural selections most awe-inspiring creations, and this is what I found:
The African Pyxie Frog
This is the second largest frog in the world and lives in regions of Africa where a long dry season defines most of the year. Amphibians aren’t generally known for their love of dry habitats and this guy has a ridiculous way of dealing with arid conditions. Every year, when the rains stop, the frog builds a mucus-based sac around its body and buries itself a metre or so below ground. And there it waits. The sac hardens to form a cocoon, and it hibernates. Typically rain returns around ten months later and reacts with the shell, dissolving it, at which point the frog returns to the surface to breed. But if the rain doesn’t come, the frog remains sheltered in its time capsule for up to seven years!
The Vampire Finch
This is one of Darwin’s famed Galapagos finches, through which he framed much of his work on evolution by noticing the drastic differences in their beaks. The difference is typically related to the foods which they consume, and that’s also true of the vampire finch: they drink the blood of other birds with a razor-sharp beak. Terrifying. And the birds from which they drink don’t seem to mind; the common rationale is that the finch used to prune them for parasites in some kind of mutually beneficial exchange, or symbiosis. The finches would benefit (from eating the parasitic bugs) and the bigger birds would be free from infection. I think that’s the saddest part – how much the victims trust them.
And just because we have cities and biologists doesn’t mean we’re free from nature’s grasp. The crushing guilt associated with being caught doing something you shouldn’t was originally churned out by natural selection to tie groups of humans together – nothing is worse (from a survival perspective) than a human being exiled from their community. And before you start to feel proud of this apparent altruism, notice that the guilt comes with getting caught. If your housemate doesn’t catch you taking their milk, natural selection does a remarkable job of encouraging you to take a little more the next day. It’s only when someone calls you out that you really start to feel concern.