Summer read: The Genetic Book of the Dead

The Genetic Book of the Dead is the latest from best-selling author and eminent evolutionary biologist, Richard Dawkins.

The book is woven with beautiful metaphors and rich descriptive language. Not so much conversational as poetic, settle in for an elaborate exploration of evolution.

Dawkins argues that the body, behaviour and genes of living creatures can be read as a book, providing an archive of ancestral information. It is peppered with curious evolutionary examples and is illustrated with a wide range of photos and diagrams that aid understanding of the associated processes.

This new book raises some new and curious questions, including whether it’s worth thinking of our ‘own’ genes as a gigantic colony of cooperating viruses.

Much like The Selfish Gene, The Blind Watchmaker and The God Delusion, The Genetic Book of the Dead is what we have come to expect from Dawkins. This new book continues to use the gene as a ‘lens’ by which to discuss evolution.

Dawkins endures as essential reading for students of evolution, as well as general audiences.

Cosmos is pleased to be able to share an edited extract from the book below.

The Species as Sculpture; the Species as Averaging Computer

Sir D’Arcy Thompson (1860–1948), that immensely learned zoologist, classicist, and mathematician, made a remark that seems trite, even tautological, but it actually provokes thought. ‘Everything is the way it is because it got that way.’

The moon is the way it is because a titanic bombardment of Earth 4.5 billion years ago hived off into orbit a great quantity of matter, which then was pulled and kneaded by gravity into a sphere. The moon’s initial rotation later slowed, in a phenomenon called ‘tidal locking’, such that we only ever see one face of it. More minor bombardments disfigured the moon’s surface with craters.

A sculpture is the way it is because a block of Carrara marble received the loving attention of Michelangelo.

Why are our bodies the way they are? Partly, like the moon, we bear the scars of foreign insults – bullet wounds, souvenirs of the duellist’s sabre or the surgeon’s knife, even actual craters from small-pox or chickenpox. But these are superficial details. A body mostly got that way through the processes of embryology and growth. These were, in turn, directed by the DNA in its cells.

And how did the DNA get to be the way it is? Here we come to the point. The genome of every individual is a sample of the gene pool of the species. The gene pool got to be the way it is over many generations, partly through random drift, but more pertinently through a process of non-random sculpture. The sculptor is natural selection, carving and whittling the gene pool until it – and the bodies that are its outward and visible manifestation – are the way they are.

Why do I say it’s the species gene pool that is sculpted rather than the individual’s genome? Because, unlike Michelangelo’s marble, the genome of an individual doesn’t change. The individual genome is not the entity that the sculptor carves. Once fertilisation has taken place, the genome remains fixed, from zygote right through embryonic development, to childhood, adulthood, old age.

It is the gene pool of the species, not the genome of the individual, that changes under the Darwinian chisel. The change deserves to be called sculpting to the extent that the typical animal form that results is an improvement.

Improvement doesn’t have to mean more beautiful like a Rodin or a Praxiteles (though it often is). It means only getting better at surviving and reproducing.

Some individuals survive to reproduce. Others die young. Some individuals have lots of mates. Others have none. Some have no children. Others a swarming, healthy brood.

Sexual recombination sees to it that the gene pool is stirred and shaken. Mutation sees to it that new genetic variants are fed into the mingling pool. Natural selection and sexual selection see to it that, as generation succeeds generation, the shape of the average genome of the species changes in constructive directions.

Unless we are population geneticists, we don’t see the shifting of the sculpted gene pool directly. Instead, we observe changes in the average bodily form and behaviour of members of the species. Every individual is built by the cooperative enterprise of a sample of genes taken from the current pool.

The gene pool of a species is the ever-changing marble upon which the chisels, the fine, sharp, exquisitely delicate, deeply probing chisels of natural selection, go to work.

When a biologist looks at fossil history, she sees not genes but things that eyes are equipped to see: progressive changes in average phenotype. But the entity being carved by natural selection is the species gene pool.

The existence of sexual reproduction confers on The Species a very special status not shared by other units in the taxonomic hierarchy – genus, family, order, class, etc. Why? Because sexual recombining of genes – shuffling the pack (American deck) – takes place only within the species. That is the very definition of ‘species’. And it leads me to the second metaphor in the title of this section: the species as averaging computer.

The genetic book of the dead is a written description of the world of no particular ancestral individual more than another. It is a description of the environments that sculpted the whole gene pool.

Any individual whom we examine today is a sample from the shuffled pack, the shaken and stirred gene pool. And the gene pool in every generation was the result of a statistical process averaged over all those individual successes and failures within the species.

The species is an averaging computer. The gene pool is the database upon which it works.

Richard Dawkins is a British evolutionary biologist and author. He is a Fellow of the Royal Society and of the Royal Society of Literature. His latest book, The Genetic Book of the Dead, is out now.