Science Sunday: Is Evolution Direction Oriented?

By: Meradeth Houston on 10:00 AM

It's Sunday! Time for a little science, okay? Yay! (Okay, maybe, not "yay!" but at least, "this might be interesting!")

So, today, I thought I'd talk about another regularly misunderstood thing about how evolution in general works. Remember, when I say the e-word, all I mean is change over time. That's all evolution is technically.

Neanderthal & Human

The thing about evolution is that a lot of people misunderstand it to be direction oriented. By that, I mean that people think that species (mostly humans) are heading always toward bigger and better. Brain size is a classic example: bigger brains and being more smart is always the way our evolution is headed, right? Um, actually, not really. Neanderthals had larger brains, on average, than modern humans (not that they were smarter than us--we don't really know that), and over the last few millenia there's actually been a trend toward smaller brains in modern humans (are we domesticating ourselves, that is the question!).

The trend in always moving forward with evolution actually stems from a very non-evolutionary concept, known as the Scala Naturae, originally proposed by Aristotle, and then later morphed into Unilineal Evolution with the understanding of Darwin's Natural Selection. The Scala then is actually an ordering of all the worlds organisms from most simple to most complex. So, single celled organisms, to jellyfish, to invertebrates, to vertebrates, to us (or, ya know, something like that). What was occasionally thought was that evolution is always trying to push things in this direction--toward the most complex and "best."

Even if Scala Naturae sounds like nonsense, I swear it's something you've heard and seen before, because it's everywhere. With humans, it's the progression of images from a stooped ape to an upright man. The thing is, this is actually not how things work.

If that's not how evolution actually works, then how does it? Well, evolution works to adapt us to our environment in the best possible way. Back to brain size: for some reason, it's been in the best interest of modern humans to have slightly smaller brains that Neanderthals, and again for our brain size to be decreasing over the past little while. Those with smaller brains have been having greater reproductive success and out-competing bigger brained people to have their genes become more prevalent in society.

Another brain size example, this time in chimpanzees: over the last 6 million years or so, since we split with our closest relatives, their brain size has decreased even more (not a ton, but still, definitely decreased). And for much of the time since that split, it actually stayed right at about the same size.

What I'm saying here is that the direction evolution takes isn't directed in any one way or another. It's not always going toward some end goal of the biggest and best (usually perceived of as humans). All it does is make us best suited for our environment through selective processes. Even if that means a smaller brain :)