I respect that minority of readers who may prefer the poetry of the Psalms, specifically 139:13 ('For you created my inmost being; you knit me together in my mother's womb.') In this How It (Fails to) Work column, though, we will stick with evolution.
So, after spending a column in the last issue saying how wonderfully evolution has created living things, how can I now say that it explains certain aspects in which we don't work? Simple. Evolution through natural selection is all about optimising organisms to succeed in doing one job in their particular environment. That job is making little copies of themselves which can, in turn, grow up and make even more copies.
Author Neal Stephenson describes this in Cryptonomicon as organisms 'spamming their environments with rough copies of themselves'. You are, Stephenson says, 'by birthright, a stupendous badass' because you are descended from a line of stupendous badasses who proved their credentials by staying alive long enough to create their offspring, your ancestors. As he says, 'Everyone and everything that wasn't a stupendous badass was dead.'
In light of this, isn't it heresy to suggest that we may not be perfect? Of course not. Perfection in not a goal of evolution through natural selection. It has no goal. It simply has results, and those results are optimisation of a whole organism for its task, not for creating perfection in any particular area of the organism.
This explains a lot.
For example, let us consider the optical illusion. Why do we see things which aren't there, and fail to see things which are?
The latter is the easiest to explain. It's all because of a gigantic screw up. When our eyes were being created by natural selection, the light sensitive cells were the wrong way around. This didn't matter at the start because those primitive eyes were merely light sensitive patches of skin, without lenses.
The connections for the signals were on the front ... the side that the light is coming from. Light comes through the lens and gets focused on the retina, which is a sheet of those cells. It penetrates past this connection to the photon counter in the cell itself. This sends a signal back to that connection. Attached to that connection is a nerve. And it's on the wrong side of the cell, of course. It, and the millions of other nerves, are gathered together and eventually have to make their way through the retina back to the brain. In other words, there is a hole in the retina to allow the nerves through. Had a better design been adopted -- with the connections and nerves at the back, instead of at the front -- this would have been unnecessary.
However it is there, that hole. We know it as the 'blind spot'. Any light falling in that part of your eye will not register. Anything happening where that light is coming from will be invisible to you.
Now how about the things that we see which aren't there? We see black dots at the intersections of white lines on a black background. We see parallel lines appearing to draw together, when they are drawn over certain other lines. We see an evenly grey bar vary in its apparent level of grey, depending entirely on the background. Then there is anything drawn by Escher. We've all seen dozens of great examples of optical illusions, some of them real, and some of them made up.
Why do we see these things which aren't there? Because they are processing bugs in our vision systems. Pattern recognition is one of the hardest programming tasks there is. I can walk out of a room and then look back into it, for the first time ever, through a window. I will recognise the room even though the angle is different and therefore all the shapes are different. Computers are quite poor at this. We, on the other, are geniuses at pattern recognition (as are all other sighted animals), and we are so within a few months of birth.
There is no way that we could afford the energy load that would be demanded by a major supercomputer, which is what would be required if we were to try to replicate this feat with technology. There would be no energy left for us make little versions of ourselves.
Capable vision is a tradeoff. Being able to see well enough helps you have little ones. Being able to see a bit better becomes a case of diminishing returns. Striving for perfection in vision would have left humanity poor at reproduction. That's because the resources poured into better vision would not have been available for other things, like fighting for the affections of, or dominance over, potential mates. Like gathering food and defending against attack. Everything is a tradeoff.
Gazelles don't run fast for the fun of it. They run fast because cheetahs run fast. Cheetahs run fast because gazelles run fast, so they'd go hungry if they couldn't. No food equals no baby cheetahs.
So our vision systems take plenty of shortcuts in all sorts of areas, including pattern recognition. They make approximations and assumptions. This makes them incredibly efficient. We do not need supercomputers in our heads.
The approximations and assumptions are based on our needs for survival and reproduction during not just our human and near human ancestry, but since the beginnings of sight perhaps half a billion years ago. For that we need to be able to notice food on a bush, spot carnivores that wouldn't mind eating us for dinner from far enough away to allow us time to escape. We never needed to precisely assess how parallel a pair of lines are.
Evolution, if I may be permitted to personalise it for a moment, never expected that we would create our own environments which are markedly different from the natural world.