The Selfish Gene

by Richard Dawkins

‘Perhaps this is the real purpose of their existence, as only a few need to survive in order for the species to be preserved’!

Perhaps one reason for the great appeal of the group selection theory is that it is thoroughly in tune with the moral and political ideals that most of us share.

We may frequently behave selfishly as individuals, but in our more idealistic moments we honour and admire those who put the welfare of others first.

Often altruism within a group goes with selfishness between groups.

unionism.

(Curiously, peace-time appeals for individuals to make some small sacrifice in the rate at which they increase their standard of living seem to be less effective than war-time appeals for individuals to lay down their lives.)

Killing people outside war is the most seriously-regarded crime ordinarily committed.

Species are grouped together into genera, genera into orders, and orders into classes.

Haemoglobin is a modern molecule, used to illustrate the principle that atoms tend to fall into stable patterns.

To try to make a man, you would have to work at your biochemical cocktail-shaker for a period so long that the entire age of the universe would seem like an eye-blink, and even then you would not succeed. This is where Darwin’s theory, in its most general form, comes to the rescue.

Before these experiments were done, naturally-occurring amino acids would have been thought of as diagnostic of the presence of life.

We tend to regard erratic copying as a bad thing, and in the case of human documents it is hard to think of examples where errors can be described as improvements.

Their modern descendants, the DNA molecules, are astonishingly faithful compared with the most high-fidelity human copying process, but even they occasionally make mistakes, and it is ultimately these mistakes that make evolution possible.

If you already know something about evolution, you may find something slightly paradoxical about the last point.

Evolution is something that happens, willy-nilly, in spite of all the efforts of the replicators (and nowadays of the genes) to prevent it happening.

Human suffering has been caused because too many of us cannot grasp that words are only tools for our use, and that the mere presence in the dictionary of a word like ‘living’ does not mean it necessarily has to refer to something definite in the real world.

Whether we call the early replicators living or not, they were the ancestors of life; they were our founding fathers.

Now they go by the name of genes, and we are their survival machines.

We are all survival machines for the same kind of replicator—molecules called DNA—but there are many different ways of making a living in the world, and the replicators have built a vast range of machines to exploit them.

A. G. Cairns-Smith has made the intriguing suggestion that our ancestors, the first replicators, may have been not organic molecules at all, but inorganic crystals—minerals, little bits of clay. Usurper or not, DNA is in undisputed charge today, unless, as I tentatively suggest in Chapter 11, a new seizure of power is now just beginning.

By force

A DNA molecule is a long chain of building blocks, small molecules called nucleotides. Just as protein molecules are chains of amino acids, so DNA molecules are chains of nucleotides.

A group of atoms bonding together, representing the smallest fundemental compound

There are about a thousand million million cells making up an average human body, and, with some exceptions which we can ignore, every one of those cells contains a complete copy of that body’s DNA.

‘Page’ will provisionally be used interchangeably with gene, although the division between genes is less clear-cut than the division between the pages of a book.

The DNA instructions have been assembled by natural selection.

DNA molecules do two important things. Firstly, they replicate, that is to say they make copies of themselves. This has gone on non-stop ever since the beginning of life, and the DNA molecules are now very good at it indeed. As an adult, you consist of a thousand million million cells, but when you were first conceived you were just a single cell, endowed with one master copy of the architect’s plans. This cell divided into two, and each of the two cells received its own copy of the plans. Successive divisions took the number of cells up to 4, 8, 16, 32, and so on into the billions.

This brings me to the second important thing DNA does. It indirectly supervises the manufacture of a different kind of molecule—protein. The haemoglobin which was mentioned in the last chapter is just one example of the enormous range of protein molecules. The coded message of the DNA, written in the four-letter nucleotide alphabet, is translated in a simple mechanical way into another alphabet. This is the alphabet of amino acids which spells out protein molecules.

Proteins not only constitute much of the physical fabric of the body; they also exert sensitive control over all the chemical processes inside the cell, selectively turning them on and off at precise times and in precise places.

embryologists

Once upon a time, natural selection consisted of the differential survival of replicators floating free in the primeval soup.

A survival machine is a vehicle containing not just one gene but many thousands.

A given gene will have many different effects on quite different parts of the body.

cross-references

inter-dependence of genes may make you wonder why we use the word ‘gene’ at all.

I said that the plans for building a human body are spelt out in 46 volumes.

The paired chromosomes do not spend all their lives physically in contact with each other, or even near each other.

In the sense that each volume coming originally from the father can be regarded, page for page, as a direct alternative to one particular volume coming originally from the mother.

A gene that is ignored in this way is called recessive.

The opposite of a recessive gene is a dominant gene.

Any given person only has two Volume 13 chromosomes.

Our genes are doled out to us at conception, and there is nothing we can do about this.

Remember that the volumes (chromosomes) are to be thought of as loose-leaf binders. What happens is that, during the manufacture of the sperm, single pages, or rather multi-page chunks, are detached and swapped with the corresponding chunks from the alternative volume.

Therefore every sperm cell made by an individual is unique, even though all his sperms assembled their 23 chromosomes from bits of the same set of 46 chromosomes. Eggs are made in a similar way in ovaries, and they too are all unique.

The real-life mechanics of this mixing are fairly well understood. During the manufacture of a sperm (or egg), bits of each paternal chromosome physically detach themselves and change places with exactly corresponding bits of maternal chromosome.

The process of swapping bits of chromosome is called crossing over.

It means that if you got out your microscope and looked at the chromosomes in one of your own sperms (or eggs if you are female) it would be a waste of time trying to identify chromosomes that originally came from your father and chromosomes that originally came from your mother.

Crossing-over is represented by taking matching paternal and maternal tapes, and cutting and exchanging matching portions, regardless of what is written on them.

In the title of this book the word gene means not a single cistron but something more subtle.

My definition will not be to everyone’s taste, but there is no universally agreed definition of a gene.

A gene is defined as any portion of chromosomal material that potentially lasts for enough generations to serve as a unit of natural selection.

The shorter a genetic unit is, the longer—in generations—it is likely to live.