Darwin gives us the low down.

I really wanted to use this blog as a way to explain concepts that I've learned in uni. After the first class (Evolutionary Psychology taught by the brilliant Dr Clare Cunningham) I quite fancy trying out this idea by explaining the very basics of natural and sexual selection. This will be a great set-up for more specific and advances ponderings later on in the year.

Let's begin.

Charles Darwin (1809 - 1882) was an interesting man. He's a testament to how successful unsure individuals can be once they find their calling; even by accident. Bill Bryson's "A Short History of Nearly Everything" is perfect for explaining the men behind the theories. I recommend it to anyone wanting to know how a man starting off studying medicine, moved to theology, and ended up on a voyage around the world accidentally uncovering the mechanic underlying the variation in all species.

The popular story of Darwin's voyage is that, whilst surveying the Galapagos islands, he noticed the vast range of physical appearances in the finches on the different islands. This isn't quite true but I haven't got Bill Bryson on hand to remind myself of the specifics. I'll edit later when I do. What became known as Darwin's finches, were descendants of a single species of finch that lived on the mainland. The different islands were far enough apart to be considered their own ecosystems, and had different food sources and environmental challenges to overcome. Presumeably, the ancestor finch species had made it to the islands somehow, and different groups settled down on different islands. How did these groups end up as completely different (unable to interbreed and produce fertile children) species?

This is where the theory of natural selection comes in. Natural selection tells us that over generations, species will change to better fit into their ecological niche. This works in two ways; the first is what is known commonly as survival of the fittest. For an example, imagine a species of rabbit which have two different colours of fur. 3/4 of the population have white fur, 1/4 of the population are black. In the countryside where these rabbits live is a species of massive big bastard birds.

These birds really like the look of the white rabbits, but are disgusted by the black. So when they swoop in to feed, they almost always eat the white ones (Flutter flutter GRAB *Squeeak*). Over time there are less and less of the white rabbits around to bump uglies with the others, so the next generations consist of more and more black rabbits. Black fur is evolutionary advantageous to the survival of the species as whole. It is naturally selected.

Sorry Milky

In order for this to work, the organisms within a species must vary, and the variations must be heritable (which definitely limits human evolution, if you think about it). Think back to Darwin's finches. On island A there were millions of insects to eat but not many seeds, so the birds with narrow beaks (good for fitting into insect holes) are selected for by their ability to eat. Narrow beaks are selected for. On island B, thick and strong beaks are selected for to crunch through the myriads nuts lying around. Over time these physical changes seperate the two groups and turn them into different species. That's natural selection.

So animals evolve through survival rates as a species, but there's another very important ingredient: Sexual selection.

Sexual selection comes in two forms, according to Darwin. Intra-sexual competition is competition between same sex individuals in the bid for happy fun time with the opposite sex. There are a number of examples of how this evolves animals. Stags evolve bigger, finer horns because those with the better antlers tend to win the fights for mates. Baboons have evolved tusk-like canines for fending off challenging males, so on, so forth. Inter-sexual competition takes place between the sexes.

The sex that uses up more resources in the reproduction process tends to become picky about mate choice. In the case of humans, females are choosier about their reproductive partners because they must spend 9 long months pregnant, go through labour, and then spend at least a couple of years weaning and looking after the kid. In evolutionary terms, they're out of the game. It makes sense that they want to choose the fellow with the best genes (ignoring the huge issue of parental investment), and so males of the species must show themselves off to be attractive choices. In such a way, traits that aren't necessarily good for survival (e.g. the typical male trait of risk-taking) are still evolved as females dig that shit. Generally speaking.

Birds of paradise are the best example of inter-sexual competition. Look at this poor fellow.

Easy target for a hawk, but gets jiggy-with-it often.

Tim, our BoP friend here, slaps open his massive colourful hood and dances about look a fool to impress the plain females of his species. This has no other use at all. None. It exists soully to impress the girls so he can have sex and reproduce. Males of most species have traits that exist for the same reason; to take advantage of the desire of females for certain traits. It sounds weird but there are little things like the square-jawed masculine look in our species that females really love in general, that have no other use but lookin' good.

In summary, females have a low reproductive potential (they can only have a child every 3 yearsish at most), but low reproductive variability (all other things equal, they are in demand and so will become mothers in their life time, all things equal.) Males have high reproductive potential (Wham bam) but high reproductive variability (they must be of a certain quality to be certain of a chance to reproduce.)

So there we go. Evolution occurs not as a conscious decision of nature, but as a result of the death or life-long dry-streak of members of a species with weaker traits. Evolution can't create anything new, it just messes with the design a bit. The details of exactly what traits are passed on are still being argued. Interesting subject though. I could've gone into the mechanic of heritability - genetic transmission - but I think I'll leave the working of Gregor Mendel for another day!

I hope this worked out well for anyone reading. I really enjoyed writing it out, It's very simple stuff right now, higher biology would give you more than you need, but as I get more advanced I'll refer back to this and you can follow with me.

Naturally.