Humans have no more genes than mice, but there's no need to feel small. Recipes are more than lists of ingredients; the cooking makes us who we areby Matt Ridley / July 24, 2004 / Leave a comment
The more we find out about genomes, the more humiliating the news they bring us. The human genome turns out to be profoundly ordinary. We have known for decades that human beings have one fewer chromosome than chimpanzees, which should have been ample warning. We have known for years that grasshoppers have three times as much DNA per cell as we do, deep sea shrimps ten times, salamanders 20 times and African lungfish a staggering 40 times. But we still kidded ourselves until just the last few years that human beings would prove to have more genes, arranged in a more sophisticated way, than most other creatures. How else to explain our exquisite brains?
We have 25,000 genes (or recipes for protein molecules) which is the same as a mouse, just 6,000 more than a microscopic nematode worm and 15,000 fewer than a rice plant. However sophisticated our brains are, it is not reflected in our genes. This has led some to suggest that we have been exaggerating the role of genes in shaping our brains. In fact, it reminds us that recipes are more than lists of ingredients. How those ingredients are cooked is also crucial. And the instructions for cooking up a body are hidden in the genome too – between the genes themselves.
The deciphered text of the human genome is being joined by an increasing number of other animal volumes on the laboratory shelf. The mouse, rat and chimp genomes are done; the fly, worm and two fish genomes have been ready for a while. The chicken is coming soon; the kangaroo and the dog will follow. Each of them is a book of stupendous length and compendious tedium in itself, written in a four-letter alphabet with no punctuation, and consisting of sometimes upwards of 95 parts gobbledegook to two parts of sense – not exactly bedtime reading.
But comparing the genomes with each other is beginning to unveil some fascinating insights. There is, for example, an intriguing difference between animals and plants, to wit that plants tend to have more genes. This seems to touch upon a fundamentally different approach to innovation employed by the two kingdoms during evolution. When plants need a new trait (or rather, when natural selection imposes an advantage on a plant that has accidentally acquired a new trait), it happens by duplication and divergence: a duplicated version of an…