Human recipes: Matt Ridley

Matt Ridley gives some interesting insights into the human genome, and that of other mammals and plants.

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.

Here are some interesting facts about the prairie vole brain:

One example: the existence of a 400-letter phrase of repetitious text in the promoter of the vasopressin receptor gene of a prairie vole turns the rodent monogamous. That phrase alters the location of expression of the gene in the rodent’s brain, making it active in the ventral pallidum, which contains a dopamine system that is responsible for addictive behaviour. A prairie vole therefore becomes “socially addicted” to its mate following sex, which is a grand way of saying it falls in love. A montane vole, lacking the 400-letter phrase, does not.

Human beings also have a repetitious phrase in this same region of the genome, though it is shorter than in prairie voles. As of this writing, the equivalent region of the chimpanzee genome has not yet been looked at. I predict it will be shorter than the human one, because humans commonly form long-term pair bonds, while chimpanzees commonly do not.

Multiply this example 10,000 or 20,000 times and you have explained how human nature differs from chimpanzee nature or vole nature. Make no mistake: this is theoretically possible. But in practice, it is an infinite task, because no sooner have you identified the “human” version than you will have to start defining how each individual slightly differs from it, and how each of those differences will cause you to recalculate the effect of the 25,000 other genes in the new context, and then the effect of those changes, and so on ad infinitum. As usual, far from closing mysteries, science opens new ones.