I have recently started to read Richard Dawkins’ book, The Greatest Show on Earth, in Which Dawkins summates all the evidence available for evolution, and puts it in a book, trying as best as possible to explain evolution to somebody who does not agree with it. It is a very interesting book to read, with plenty of interesting examples from nature and analogies, which have enhanced my knowledge of evolution and how to explain it to others.
While I was reading, I came across an analogy which I just had to hear, which answers a question often raised in rebuttal to evolution. When talking with a creationist, the idea that genetic diversity cannot occur often comes up (in contrast to the genetic diversity of the human species from just 2 humans? But that’s another story). They say that in a population, genetic diversity cannot occur. They make an analogy with genes as paint. If you take a species, which ranges in colour from red to blue, and you go about procreating, every time you mix two animals, you will only get closer and closer to purple, and genetic diversity will shrink. Eventually, all you will be left with is purple. How can evolution happen if it works like that.
Dawkins argues that evolution does not work like this. In fact, it works quite differently. He proposes that instead of mixing paint, it is best to imagine evolution as shuffling cards. This is how evolution works, and the evidence is right in front of us.
By imagining evolution as card shuffling, it is much easier to get the idea of evolution. Instead of animals being created by mixing of paint, it is more like they are having two decks of cards shuffled together. In this way, instead of just ending up with a disgusting purple mess, you end up with the world as it is today.
This can be used to explain our tweaking of the canine species. Say for some reason a breeder wants to lengthen the tail of Labradors. When he does it, he picks the Labradors which have the most ‘long tail’ genes (cards), and goes about creating a new species. By isolating these dogs with longer tails from the dogs with shorter tails, you can ensure that more and more ‘long tail’ cards remain in the sub-species every time you shuffle the deck.
The logic behind this ‘shuffling and re-ordering’, as opposed to mixing, is actually pretty clear and is presented to us roughly every 5 seconds. When you breed a man and a woman together, one who subscribes to the ‘mixing’ analogy would expect the baby to come out as a hermaphrodite. Instead, this doesn’t happen, we get either a boy or a girl. This is just the mixing of a deck of 1 card. With one card having M on it, and one card having F on it.
Now, imagine this happening with the whole genetic code. Instead of just the one gene for gender (gender isn’t determined by genes, but it makes no difference to the analogy), you have this going on with every single gene in the code. When a baby is being ‘made’, this process will be occurring. Take a single gene in the code. If the mother has gene A, and the father has gene B, the baby will not have a mixture of A and B as their gene, they will get either ‘A’, or ‘B’. This happens all along the code.
Hopefully, I’ve done a good job at explaining this analogy, and haven’t butchered it. That’s all, by shuffling of cards, not mixing paint, with occasional cards falling out of the deck, or 2 being stuck together and coming apart due to plenty of shuffling, you get evolution.