So Shall We Reap by Colin Tudge

Author:Colin Tudge
Language: eng
Format: epub
ISBN: 9780141927312
Publisher: Penguin Books Ltd
Published: 2009-03-11T04:00:00+00:00

Phase II: Formal Breeding before Genetics

We cannot know what went through the heads of the world's first farmers as they began to transform wild plants and animals into crops and livestock. They may from the first have dreamt of more succulent roots, or fatter and more fecund beasts. Or they may not. Either way, they certainly could and almost certainly did effect significant changes even without any clear idea of what they wanted to achieve – or indeed without realizing that the recalcitrant roots and beasts they strove to control and propagate could be transformed by deliberate strategy into something more agreeable.

But it's also clear that at some time in the distant past, farmers did realize that they could change the creatures they sought to manage; moreover, that they could nudge them step by step towards some specified ideal; and so their inadvertent inroads processed into conscious policy. The shift had clearly taken place by classical times: the peoples of the Mediterranean and Middle East who relied so heavily on horses, for example, certainly knew what they wanted, and how to select and match the stallions and mares appropriately. Farmers who strive consciously to tailor crops and livestock can properly be called ‘breeders’. Those who operate(d) without the aid of modern genetics theory can be called ‘craft breeders’.

The essence of craft breeding is common sense – plus endless experience and knowledge of detail, for nature is not in the end constrained by common sense and sometimes it pays to go down routes that are counter-intuitive (sometimes feeble-looking individuals that instinct tells you to throw out provide just the complement of genes that's needed). Common sense says that if you want to breed a bigger ear of corn, or a fatter pig or a fancier goldfish, then you save those individuals in any one generation that come closest to the ideal: allow them to breed, and eat, sell, or otherwise dispose of, the rest. This is (artificial) ‘selection’. Common sense says, too, that if one individual shows one set of desirable characters (biologists use ‘characters’ to mean ‘features’) and another individual has different characters that are also desirable, that a marriage between the two could produce offspring that combine the best of both. This is ‘crossing’. Judicious selection and crossing are the essence of all improvement programmes.

In practice, there are two main strategies. One in essence is simply to select the best individuals in any one generation, and match them with others who have complementary qualities: ‘Cross the best with the best and hope for the best’, as breeders say, in self-disparagement.

The other is ‘mass selection’: the breeder (or farmer) has some ideal in mind, and allows all those individuals who roughly conform to the ideal to interbreed freely with each other, and throws out the rest. Henry VIII was proposing mass selection when in 1541 he decreed that stallions under 15 hands (142 cm) in height should not be allowed to graze on common land in the Midlands and south of England (thus effectively signing their death warrants).

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