- Genes create fractal patterns
- Genes are the primary unit of evolution
- Genes maximise their own survival
- The co-operation paradox
- Gendered genes
Genes create fractal patterns
Repeating (and fractal) patterns appear in living things because genes are used multiple times to create physical objects at different scales.
In a tree, the trunk, and branches, and smaller branches are all created by the same gene, which means the same pattern is repeated. This creates a fractal pattern of branches. It ends at the leaf.
In humans, we are mirrored, symmetrical on our left/right. The same genes groups code for both sides of our body, just inverted.
And our cells themselves all have a similar structure, with modifications, and it's all coded from the same piece of DNA. Used billions of times over, and then tweaked, according to the function of each larger organ.
Repetition is how DNA creates such complex structures.
All of this is also super complicated to work out, and our understanding of how it all plays out in our own bodies is very, very limited.
This leaf is created by a simple repeating mathematical formula.
Genes are the primary unit of evolution
Genes are the primary units of evolution. It's better to think of a population as a gene pool rather than a lineage of individuals.
Another aspect of the particulateness of genes is that it does not grow senile; it is no more likely to die when it is a million years old than when it is only a hundred. It leaps from body to body down the generations, manipulating body after body in its own way and for its own ends, abandoning a succession of mortal bodies before they sink in senility and death.
The genes are the immortals, or rather, they are defined as genetic entities which come close to deserving the title. We, the individual survival machines in the world, can expect to live a few more decades. But the genes in the world have an expectation of life which must be measured not in decades but in thousands and millions of years.
In sexually reproducing species, the individual is too large and too temporary a genetic unit to qualify as a significant unit of natural selection. The group of individuals is an even larger unit. Genetically speaking, individuals and groups are like clouds in the sky or dust-storms in the desert. They are temporary aggregations or federations. They are not stable through evolutionary time. Populations may last a long while, but they are constantly blending with other populations and so losing their identity. They are also subject to evolutionary change from within . A population is not a discrete enough entity to be a unit of natural selection, not stable and unitary enough to be 'selected' in preference to another population.
An individual body seems discrete enough while it lasts, but alas, how long is that? Each individual is unique. You cannot get evolution by selecting between entities when there is only one copy of each entity! Sexual reproduction is not replication. Just as a population is contaminated by other populations, so an individual's posterity is contaminated by that of his sexual partner. Your children are only half you, your grandchildren only a quarter you. In a few generations the most you can hope for is a large number of descendants, each of whom bears only a tiny portion of you—a few genes—even if a few do bear your surname as well.
Individuals are not stable things, they are fleeting. Chromosomes too are shuffled into oblivion, like hands of cards soon after they are dealt. But the cards themselves survive the shuffling. The cards are the genes. The genes are not destroyed by crossing-over, they merely change partners and march on. Of course they march on. That is their business. They are the replicators and we are their survival machines. When we have served our purpose we are cast aside. But genes are denizens of geological time: genes are forever.
Genes, like diamonds, are forever, but not quite in the same way as diamonds. It is an individual diamond crystal which lasts, as an unaltered pattern of atoms. DNA molecules don't have that kind of permanence. The life of any one physical DNA molecule is quite short—perhaps a matter of months, certainly not more than one lifetime. But a DNA molecule could theoretically live on in the form of copies of itself for a hundred million years. Moreover, just like the ancient replicators in the primeval soup, copies of a particular gene may be distributed all over the world. The difference is that the modern versions are all neatly packaged inside the bodies of survival machines.
What I am doing is emphasizing the potential near-immortality of a gene, in the form of copies, as its defining property. To define a gene as a single cistron is good for some purposes, but for the purposes of evolutionary theory it needs to be enlarged. The extent of the enlargement is determined by the purpose of the definition. We want to find the practical unit of natural selection. To do this we begin by identifying the properties which a successful unit of natural selection must have. In the terms Of the last chapter, these are longevity, fecundity, and copying-fidelity. We then simply define a 'gene' as the largest entity which, at least Potentially, has these properties. The gene is a long-lived replicator, existing in the form of many duplicate copies.
Genes maximise their own survival
The logic is practically mathematical: A gene that results in reproduction, or a higher rate of reproduction, will always become more prevalent than those that do not. After many generations, the vast, vast majority of genes that exist will be those that ensure their own survival, sometimes at the determent of other genes. This mechanism is perhaps the most fundamental property of life.
The co-operation paradox
But now we seem to have a paradox. If building a baby is such an intricate cooperative venture, and if every gene needs several thousands of fellow genes to complete its task, how can we reconcile this with my picture of indivisible genes, springing like immortal chamois from body -to body down the ages: the free untrammelled, and self-seeking agents of life? Was that all nonsense? Not at all. I may have got a bit carried away with the purple passages, but I was not talking nonsense, and there is no real paradox. We can explain this by means of another analogy.
One oarsman on his own cannot win the Oxford and Cambridge boat race. He needs eight colleagues. Each one is a specialist who always sits in a particular part of the boat—bow or stroke or cox etc. Rowing the boat is a cooperative venture, but some men are nevertheless better at it than others. Suppose a coach has to choose his ideal crew from a pool of candidates, some specializing in the bow position, others specializing as cox, and so on. Suppose that he makes his selection as follows. Every day he puts together three new trial crews, by random shuffling of the candidates for each position, and he makes the three crews race against each other. After some weeks of this it will start to emerge that the winning boat often tends to contain the same individual men. These are marked up as good oarsmen. Other individuals seem consistently to be found in slower crews, and these are eventually rejected. But even an outstandingly good oarsman might sometimes be a member of a slow crew, either because of the inferiority of the other members, or because of bad luck—say a strong adverse wind. It is only on average that the best men tend to be in the winning boat.
The oarsmen are genes. The rivals for each seat in the boat are alleles potentially capable of occupying the same slot along the length of a chromosome. Rowing fast corresponds to building a body which is successful at surviving. The wind is the external environment. The pool of alternative candidates is the gene pool.
As far as the survival of any one body is concerned, all its genes are in the same boat. Many a good gene gets into bad company, and finds itself sharing the body with a lethal gene, which kills the body off in childhood. Then the good gene is destroyed along with the rest. But this is only one body, and replicas of the same good gene live on in other bodies which lack the lethal gene. Many copies of good genes are dragged under because they happen to share a body with bad genes, and many perished through other forms of ill luck, say when their body is struck by lightning. But by definition luck, good and bad, strikes at random, and a gene which is consistency on the losing side is not unlucky; it is a bad gene.
Splitting ourselves into two genders is simply a way of mixing up genes. Far better in creating variation than waiting for individual mutations. Clearly an organism would seek to mix its genes with a partner with high quality genes.
However, having good genes of your gender has become a pretty major part of reproduction, so much that it's got its own name- sexual selection, rather than the quality if genes as a whole.
Perhaps later, if we have an extremely technologically advanced future, we can have a child (mix genes with) anyone, not just the opposite sex, and these barriers might start to come down.
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