Beaky flappy wings

It was hell in the playground. All the other birds teased Bobby. Long beak, big, ungainly wings. 'Beaky Bobby flappy wings' they called him. 'You're not normal' they said. Mr Smith his teacher tried to console him (he sympathised with anyone who was having a hard time right now) 'Let's explore what we mean by normal' he said and went off into a lecture when all Bobby really wanted was a new pair of trainers.

What Mr Smith outlined was worth noting though.  In population terms, normal has a special meaning. If you take a random sample of any population and measure a characterstic (length of beak for example), you will find the sizes vary around an average. If you chart it on a graph you get the famous bell shaped curve. Some beaks are longer than others, some shorter, but 99.9% of the population will be within 3 standard deviations of the average. (Don't panic, Bobby comes back in a minute). Normal is anything in this range. Bobby (there I told you he would be back) might have an unusually large beak, but he is still normal.Who needs specialist counsellors when you've got statistics?

It is however the way evolution (sorry for swearing) works. Unless a change or an extreme actually does harm to an organism's chance of survival, the change just stays and gets inherited. In fact most organisms are simply an accretion of random changes.

Lets go back to Bobby. His friends are still giving him grief, but they are all getting thinner. It's been a particularly harsh winter and all the normal fruit has been eaten. But no problem for Bobby. He has a long beak and can just penetrate a fruit that none of his friends have ever eaten. It's delicious. And nutritious. Of course, there are quite a few others who have similarly long beaks as Bobby, but they just don't have the wing power to fly high enough to reach. Others have the wing power, but not a long enough beak. It turns out these random, statistical variations have come good. Strange how all the girl birds seem to fancy Bobby not his increasingly scrawny class-mates....

One of the key objections levelled against the theory of evolution is that there is no mechanism for complexity to develop. But there is. Statistics and probability. Random changes, variations. The lethal ones die out, those that aren't just stay. Occasionally a collection of random changes gives an advantage, more often a change in environment turns a neutral or mildly positive set of changes into a real winner. A piece of skin that is light-sensitive and of no use. Hangs around for generations. Another random change - the shape of the skin becomes slightly concave so that light gathers onto the sensitive patch. Again, for generations, no advantage - just a very small sub-set of the population with both characteristics. Then some of this sub-set randomly develop a reflex that moves away from light - others develop one towards light. Finally, after generations of it not mattering something in the environment changes. It doesn't matter what. But anything in the dark dies. Now, what was an extremely small population becomes almost overnight the only population. Now all the descendents will have these characteristics and a new set of random additions can begin.


Mr Smith got home from school. 'Have you seen the price of fruit?' he asked the house in general. 'You'd need to win the lott.....' Heads in hands, he turned round and decided a long walk might be in order.

What does it all mean? Find out on Thursday...