Okay, here’s something that I feel like the Cosmos show did nicely – when they showed a tree representing evolutionary lineage, humans were on a branch jutting out seemingly at random to the side. Whereas many popular science presentations of evolution depict humans as the pinnacle – we’re here at the top, and if you go back in time, our ancestors looked like chimpanzees, and if you go back farther in time, our ancestors looked like goldfish, and if you go back farther in time, our ancestors looked like sea sponges… which obviously isn’t true. A current chimpanzee, and a current fish, and a current sponge, have gone through just as much evolutionary time as we have.
I think many scientists would feel bothered by phrasings such as “humans are more evolved than bacteria.” Well, a statement that direct might be hard to come up with a reference for, but quite often humans are described as “higher organisms,” in comparison. And, yeah, we are multicellular, and have nuclei – gee whiz, nuclei! But you could quite easily argue that bacteria are more evolved. Their generational time is shorter, so every minute effectively gives them more time to evolve than it gives us. And they seem quite well suited for their environment – many can now thwart even directed efforts to expunge them. I’d like to see some of those “highly evolved” humans shrug off murderous intent with such panache.
And, honestly, that was going to be the end of my essay. I was planning to root around, find an egregious reference for a statement about how great it is that humans are so evolved, and call it finished. But would that be cool? I have to imagine that plenty of high school biology teachers out there have already declaimed similar truths to their students.
So, instead, here is a bonus contrasting thought – a framework in which humans are, in fact, more evolved.
Because, sure, bacteria go through many more generations than humans within any given amount of time. But additional “rounds” of evolution won’t accomplish much if there aren’t significant options for change. A wide range of bacteria all look pretty much the same… to me, that is, someone who is not a bacteriologist. The times I’ve looked at them in microscopes, they just looked like bothersome squirming dots – I was doing mammalian tissue culture, so was displeased to see them, and was using relatively low magnification. And to someone who actually knows about bacteria, the idea that they’re all the same might sound inane – some polymerize mammalian actin behind them to shoot around like rocket ships! How is that not cool??
Well, yeah, yeah, actin rockets.
A lot of the problem, in terms of my thinking that various evolutionary descendants of bacteria are cool, is that they function much closer to the thermodynamic limit than other organisms do. Not so much that I think it’s reasonable to generally assume that they function efficiently – yes, a mathematical model under that assumption reproduced rRNA copy number, but how many other salient features of the genome would be predicted? – but the energetic constraints on bacteria do seem to be tighter than for many multicellular organisms. If you are competing for resources based on reproduction rate, and a limiting step is duplication on your genome, there’ll be strong pressure to keep your genome small. But one major driver of evolutionary divergence is gene duplication events – it’s easier to accrue mutations that might lend a new function if those mutations are in a second copy and do not necessitate the loss of a necessary pre-existing function.
So a multicellular organism, with a big sloppy genome, has a lot more tuning knobs that can be adjusted during evolution. Which I thought was worth writing about because it would allow me to make a cutesy analogy to the current design goals of the team making League of Legends. It’s a twitchy online variant of capture the flag that I used to play – I can’t anymore, since they made the game fancier and I’m using a computer from 2006 that needs a lot of duct tape to function. At the four corners of the base, duct-tape holds stacks of 3 pennies each to give my computer stilts so that there’s room for the fan to exhaust and space for the battery to hang out. Pennies seemed cheaper than buying pegs or anything to keep it raised. And, right, the battery – it’s gotten bulgier over time, such that now, if it’s put all the way into the computer, it presses against the underside of the keyboard and makes many letters not work. But as long as it dangles halfway out all the time, kept in place with duct tape, the computer works fine.
I’m sure a bulging battery doesn’t indicate anything potentially disastrous, right?
Anyway, the League of Legends team recently announced their goals for the new changes, and one they stressed was that they wanted to give themselves more potential variables to tweak in case the game needed balancing in the future. And I thought, okay, that’s a sense in which you could claim that humans are more evolved – we have so many features that can be tweaked over time, compared to the set of variables available to be modified during bacterial evolution.
But a corollary to that thought is that, since there are so many variables that could change with humans, and since we have a relatively long generational time, there’s no reason to expect that we’ve gotten much right yet. With a bacterium, you might expect that it will be sufficiently evolved that it’s near optimal for its environment. With a human, you should have no such expectation.
Which I was writing about in my project as regards transcranial electrical stimulation. This is a technique where you deliver excess current to certain regions of your brain with the goal of improving cognition – it often seems to work, although there have been only vague explanations why. And the very fact that something like this might work illustrates that human evolution didn’t get incredibly far. Much of our reproductive success is due to cognitive ability – that’s how we were able to cover the globe, and begin altering environments to suit us better (locally – globally, we may well be doing the opposite), and contemplate shooting ourselves into space. So you might imagine that there would be evolutionary pressure on humans to make that cognitive ability as good as it can be. Which obviously isn’t the case if you could look at a cheesy website and build something out of supplies from Radioshack to make yourself think better.