Saturday, August 20, 2011

Evolution

There are three very common accusations that are repeatedly levelled against the theory of evolution. They're all fundamentally flawed accusations but they are used constantly in an attempt to discredit the theory. Two of the criticisms are even, strictly speaking correct, but that does not make them credible criticisms - it is simply a misunderstanding of terminology. The three accusations are as follows

  • It's just survival of the fittest
  • We're all descended from monkeys
  • It's only a theory

It's Just Survival of the Fittest


Survival of the fittest is a phrase that now tends to be avoided in science because it has become so widely misunderstood. It is most commonly interpreted as kill or be killed. The logical but flawed conclusion of kill or be killed is that if you are able to kill and live off another species then ultimately you will wipe that species out - that is most commonly understood to describe survival of the fittest.

Survival of the fittest however has a more nuanced definition than that. Survival of the fittest means the ability of a species to survive despite the existence of its predators. It is the ability to reproduce in sufficient numbers that you cannot be wiped out.

Consider the ant and the anteater. The anteater by definition, eat ants. It has done so for millions of years but it has so far failed to wipe out the ant population and in fact, the demise of the ant population would very quickly result in the corresponding demise of the anteater population. The anteater has no interest in eating all the ants in the world so there are none left and the ant has developed the ability to reproduce in sufficient numbers that it can continue to survive, despite relentlessly being eaten by anteaters. This makes the ant fit for survival and an excellent illustration of the phrase survival of the fittest. The ant is a very fit creature. As a species, it'll probably outlive us all.


We're All Descended from Monkeys


We're not. The theory of evolution states that we, and monkeys, share a common ancestor. It does not state that we are descended from a species that exists alongside us nor does it claim to know what that common ancestor is. That would be ridiculous.

The common ancestor the theory states we share has long since departed the planet and we have no idea what form it might have taken (we're probably talking primordial soup here) but there are sufficient similarities between us and other species to conclude that, despite our lack of absolute knowledge about that ancestor, we can still almost certainly conclude it was shared.


It's Only a Theory

Yes, that's correct. It is only a theory. But to dismiss it as simply being a set of ideas which have somehow gained a fashionable following which is what people are implying with this criticism is wrong. It fails to acknowledge the correct scientific definition of a theory.

A scientific theory is an idea which is constantly tested and whilst it may never be proven to be fact gains creedence over time the more it is tested with additional data. Many theories are accepted as fact despite science continuing to describe them as theories because science does not allow something to be described as fact unless it can be definitively and unquestionably proven as such. Theories simply become more credible as more and more data is pumped through them and the theory continues to hold up. It may however never be possible to prove a theory is fact because you may never have access to all the data.

Consider the following example. I choose to measure the height of all adult members of my family. The heights of these people are facts. I could, based on these facts, develop a theory that the average height of any adult person is five feet and six inches. That would be a poor theory (not enough data) but a theory nonetheless. I would need a lot more data to make it a plausible theory.

If I then measured all the people in my street I might refine my theory and state that the average height of any given adult person is five feet and five inches. I still could not describe this average height as a fact but I've just made it a more reliable theory. I could then measure all the people in London and I might still have the theory that the average height of any given person is five feet and five inches. The theory is looking better and better.

I could spend the rest of my life measuring people and come up with an incredibly accurate figure for the average height of any given person. That average figure would eventually reach a point where regardless of how much more data I fed into it, it would barely change. You might then be able to say this average figure is a fact, but in absolute scientific terms it would still be only a theory.

For my theory to be accepted as fact I would need to absolutely know the height of all people. I would need all the data. The theory of evolution has had a lot of data fed into it and continues to hold up but yes, it's still only a theory but after all this time and all this data, it's a bloody good one.

6 comments:

Terra Shield said...

In a discussion about evolution vs creationism, someone once told me that the fossils were put there by God to fool us all. I was so shocked that I didn't know how to react.

I happen to be reading The Descent of Man (not the full version, though) right now.

King of Scurf said...

Terra: God is playing tricks on us? That's a new angle I had not heard before.

How brave of you to tackle The Descent of Man. I suspect it's pretty dense.

Nota Bene said...

I know some people that are definitely descended from apes, and not very far at that...but on a serious note, it's a good theory to have around

King of Scurf said...

NB: I think we all know a few people who skipped a couple of links in the evolutionary chain. Thanks for stopping by.

nursemyra said...

Were you a teacher in another life?

King of Scurf said...

nursemyra: This post does rather have the musty whiff of the old schoolbook about it and I don't much like it for that reason.

I have never been a teacher in this life or any others I suspect apart from a little software training here and there. I don't have the patience to teach but I do like thinking of analogies.