Keeping it simple
Two great questions about evolution in recent posts in response to my evolution blogs, and here is the second one. One of my readers asks ‘How does an irreducibly complex structure appear in the first place? It can’t evolve up from from something simple, right? How does a functioning whole come into being from parts? Aren’t even the simplest building blocks complex structures? How did the first one come into being?’

This is another one of those cases where you read something and a light bulb goes off and you think, ah, that’s the problem, that’s the reason for the lack of comprehension. And then you think, yes, and this lack of comprehension is why children all over the world are being taught ‘intelligent design’ in the year 2006, a concept so simple minded that it was discredited 150 years ago.

Is the human body ‘complex’? You betcha (but no more ‘complex’ than the bodies of gorillas and chimps and whales and sheep and bears and kangaroos and mice, and arguably less complex, in some ways, than the bodies of birds and snakes and fish). Did the ‘complex’ bodies of humans (and all other modern animal species) evolve directly from the ‘primeval slime’? Of course not. Did they evolve from it indirectly over a long period of time? Of course.

One big problem is the word ‘complex’. Evolution doesn’t work to make bodies more complex but more functional. Sometimes this might result in increased complexity, sometimes in increased simplicity. If by complexity people mean bodies with a lot of different organs then a human body is less complex than sheep or cattle which have very complex ‘stomachs’ or rabbits which have a functional caecum where we only have the remains of a non-functioning reduced caecum (an appendix). Birds have arms modified for flight, and bones modified to be light, fish have swim bladders instead of lungs, and so on. Fish can also analyse pressure variations in water, and some can analyse electrical signals, bats can send and receive very high frequency sounds in a process like radar, snakes can taste the air and receive vibrations through the ground, we can’t do any of that stuff. The complexity concept makes no sense at all.

Nor does the concept of ‘irreducible complexity’. Complexity is always being reduced, modified, converted to a different kind of complexity, lost completely, made over again from a new starting point, throughout evolutionary history. The human body (and that of chimps, sheep …) isn’t an example of a perfectly designed machine, but a grab bag of bits and pieces put together over a long time. It far more resembles a sculpture made from junk than a Swiss watch. If you take any organ in the body. ANY organ. And trace it back through evolutionary history you will see how it has evolved through more and sometimes less complex stages, ultimately back to the first multicellular species. In many ways the big evolutionary jump was not from simple animals to complex ones but from single celled to multi-celled species (although even that may not have been such a big deal at the time – two cells which have failed to separate fully after division can potentially swim faster than any one cell, and so on). Once you have a body with many cells, then the challenges of preventing water loss, moving, taking in oxygen, absorbing nutrients, getting rid off excess fluids and waste products, circulating oxygen and nutrients, responding to stimuli from outside the body, reproducing, can all be done in many different ways and combinations. And initially some of those ways will be quite simple – for example a straight gut with little difference from front to back, and later that gut will become longer and more coiled and with different functions along its length – more complex if you like. Both guts will function very well, and so will the intermediate stages. And this is not theory, we can see all those different ways in both the modern species and in the fossil record.

And, finally, of course complex structures are made up of simple parts. The bodies of all multi cellular animals are made of many cells. All organs are made up of cells, in various combinations and functionalities. All cells are fundamentally the same, but can become specialised, and the combinations of specialised cells are what make up complex organs.

All of that makes sense when evolution is the result of natural selection operating on mutations in a varied and changing environment. What doesn’t make sense is that an intelligent designer would come up with a middle ear made from what were originally jaw bones, or an appendix, or an upright species with a back designed for walking on all fours.

20 May 2006