Anyhoo, I consider evolutionary biology to be among the most important of the sciences, particularly in terms of understanding our place in the universe. And no living biologist has had quite as much impact as Richard Dawkins with his Selfish Gene. As such, I've extracted a chunk of my book, which attempts to give the reader a taste of the power of present evolutionary theory. Again, comments and feedback welcome, ESPECIALLY if I've made a boo-boo:
The only way I could possibly write this without feeling tremendously guilty is by stating here and now that what I’m writing here is a drastically abbreviated account of one of the most amazing facets of modern evolutionary biology. As such, if, after my humble introduction you are in fact interested in learning more, then I must point you towards The Selfish Gene by Richard Dawkins. The long story short is as follows.
You are probably at the very least familiar with some of the basic premises of evolution, i.e. that it involves organisms slowly changing over the generations as they mutate and favourable mutations survive to breed future generations and less favourable mutations die out. The trick is to view evolution not from the point of view of the individual organism, but from the perspective of it’s DNA (or RNA in the case of simpler organisms, if you want to be pedantic). For simplicity, I’ll just refer to DNA and start my story in the middle.
Think of an organism, say, a cat. In order to make copies of itself, a cat’s DNA has over the generations, produced an organism with all the necessary traits for survival, i.e. limbs to get around with, a digestive tract to process raw materials, a reproductive system to create copies of itself, etc. From all outward appearances, a cat appears to be a beautifully designed machine.
Hundreds of generations ago, a cat may not have been quite as it appears to you today. Such a proto-cat would perhaps be less well-formed. And somewhere down the line, along comes a mutation - bigger ears, perhaps, or longer legs, rougher tongues or some such. What matters is how such a mutation contributes to our proto-cat’s chances of survival and here’s the bit where survival of the fittest comes in:
- If the mutation INCREASES the gene’s chances of survival, this new superior organism could become dominant and slowly replace the original.
- If the mutation DECREASES the gene’s chances of survival, odds are it expires before passing on its inferior genes to the next generation and that’s the end of that.
- If the mutation makes no real difference to the gene’s chances of survival, you get a possibility of a new breed of organism exploring a new evolutionary path.
When we look at the nature’s wonders around us today and think about the randomness inherent in natural selection, it’s easy to liken the result to rolling 1,000 sixes on 1,000 dice. How is such complexity and perfection possible? This is where most people with an inadequate understanding of natural selection go drastically wrong. The result is most certainly like rolling 1,000 sixes, but in the case of natural selection, it’s more correct to say that one rolled 1,000 dice, then removed anything that didn’t roll a six and rolled again. So, after the first attempt, going by simple averages, say 1 out of every 6 dice give you a 6. That gives you about 167 sixes, so you keep those, and reroll the rest. Here’s a quick table showing the results of each iteration:
Keep this up for long enough after a total of about 35 iterations you should have a fair chance at arriving at your 1,000 sixes.
By comparison, if you were to try and roll 1,000 dice and coming up all sixes the HARD way, that is, without this mechanism of selection, you’ll be rolling dice well into the 5th or 6th death and rebirth of the Universe and in all likelihood won’t come anywhere close.
The term Darwinism is often used to describe the process of ruthless judgement by Nature of an organism’s worthiness to exist. The bit where the selfishness of the gene comes in is when we observe that the purpose of the gene is to propagate itself, often with little to no regard for the organism carrying the genes.
For example, black widow spiders and praying mantises both practice mating habits that don’t end well for the male. An understatement, I suppose; the males get eaten by the female shortly after mating. From the point of view of the individual organism, this is, of course, very, very bad. However, it appears that this suicidal act increases the males’ chances of fertilising the eggs, and from the genes’ point of view, that’s all that matters.
Another example closer to home is the existence of junk DNA in our genome. About 70% of the human genome has no apparent purpose in the construction of an individual human. So why is it there? Very simple: that “junk” DNA does not “care” what it does for us. It’s there because it’s carrying out its purpose of replicating itself. Apparently, at some point in time, part of those genes’ survival strategy involved hitching a ride inside the genome of some hapless creatures (i.e. us), so there it is, freeloading on our genome to this day.
The selfish gene treats genes very much like incredibly advanced viruses, existing for the sole purpose of replicating themselves. The great diversity of life we observe today are a reflection of all the different strategies explored by genes to propagate themselves, each organism being a “survival machine”, to quote Richard Dawkins. This brings us to another fascinating concept, also introduced in The Selfish Gene: The meme.
The thing to bear in mind is that the evolution of genes alone is NOT enough to explain the development of humans. We're a bit odd like that. An example I can point to is our brains, which are disproportionately large compared to those of similarly sized mammals. And they gobble a LOT of energy, too! Why humans, when other animals seem to get along fine without?
Stay tuned, and I'll (eventually) tell you a tale of memes. Alternatively, bugger off and pick up a copy of Susan Blackmore's The Meme Machine.