Prof Campbell: The issue of missing links is an old problem, and one that Darwin himself addressed in the Origin. The reason is that the fossil record is but a tiny fraction of all the organisms that have existed on the Earth over the past 3800 million years. At present there are some 6000 million humans living. In a million years time perhaps just a few hundred fossils will be found. This wouldn't even be enough to tell how many different ethnic groups there were, let alone look for 'missing links'.
Question 26
What is the underlying drive that makes us and other species want to breed? Just to carry our genes and improve our race? Why does it feel so natural?
Prof Campbell: This is classic example of natural selection in action. Only those organisms that have found a mechanism or desire to reproduce will have produced offspring that we experience today. Did the dinosaurs get bored with sex? Is this why they died out? But remember sex isn't just for mating. In humans we are very unusual that our children have to be looked after for some 15 years before they can pass on their DNA. Sex is a crucial binding agent keeping father and mother together. That's why today if sex is OK in a marriage it can survive most ups and down. If the sex is no good or non-existent then a relationship can survive, but more commonly it breaks down.
Question 27
What determines whether a gene swings into action or remains repressed or the great leaps in evolution such as a fish becoming an air breather?
Prof Campbell: The expression of genes is regulated by positive and negative mechanisms in each cell. As I argued in Campbell, AK (1994); Rubicon: the fifth dimension of biology, Duckworth. Natura non facit saltus(m) – Nature makes no leaps, Darwin argued in many places in the Origin and elsewhere. But was he right? I think not. The key problem in evolutionary theory now is to unravel the molecular pathway that led to a particular Rubicon, only after this is crossed can evolution of a process occur through natural selection. Darwin recognised this problem in Chapter 4/6 on the Origin – Difficulties on/of theory. These were his difficulties. My own field of bioluminescence was one of particular difficulty. How did a chemical reaction evolve before it was visible to another individual?
Question 28
If our brains evolved and not created why do we use such a small percentage of its power throughout our short lives?
Prof Campbell: That is the beauty of natural selection. It tells us that there has to be a selective advantage to this apparent over-capacity of the brain. One obvious reason is the issue of memory. Our neurones are dieing all the time. As one neurone dies in a network it has to be replaced or the network will fail. This is the problem in dementia, neural networks break down and so memory goes.
| « Back: Questions 21 - 24 | Next: Questions 29 - 32 » |
