An active replicator is any replicator whose nature has some influence over its probability of being copied. For example a DNA molecule, via protein synthesis, exerts phenotypic effects which influence whether it is copied: this is what natural selection is all about.
A passive replicator is a replicator whose nature has no influence over its probability of being copied.
A further important point is that Maynard Smith was seeking the ‘best’ strategy in only a special sense. In fact he was seeking an ‘evolutionarily stable strategy’ or ESS.
Many people have noted the contrast between the hysterical ‘hurt’ professed by Muslims and the readiness with which Arab media publish stereotypical anti-Jewish cartoons. At a demonstration in Pakistan against the Danish cartoons, a woman in a black burka was photographed carrying a banner reading ‘God Bless Hitler’. In.
If a program or strategy is successful, this means that copies of it will tend to become more numerous in the population of programs and will ultimately become almost universal. It will therefore come to be surrounded by copies of itself. If it is to remain universal, therefore, it must be successful when competing against copies of itself, successful compared with rare different strategies that might arise by mutation or invasion.
Nevertheless, it is a common error, which we shall meet again, to leap from the premise that the question of God’s existence is in principle unanswerable to the conclusion that his existence and his non-existence are equiprobable.
I shall be using the name ‘history-deniers’ for those people who deny evolution: who believe the world’s age is measured in thousands of years rather than thousands of millions of years, and who believe humans walked with dinosaurs.
To recapitulate, the significance of the difference between growth and reproduction is that reproduction permits a new beginning, a new developmental cycle, and a new organism which may be an improvement, in terms of the fundamental organization of complex structure, over its predecessor.
The whole purpose of our search for a ‘unit of selection’ is to discover a suitable actor to play the leading role in our metaphors of purpose.
Most of the DNA molecules in our bodies are dead-end replicators. They may be the ancestors of a few dozen generations of mitotic replication, but they will definitely not be long-term ancestors.
When we talk of a program as ‘doing better’ or as being ‘successful’ we are notionally measuring success as capacity to propagate copies of the same program in the next generation: in reality this is likely to mean that a successful program is one which promotes the survival and reproduction of the animal adopting it.
Although a good God regrets our suffering, his greatest concern is surely that each of us shall show patience, sympathy and generosity and, thereby, form a holy character. Some people badly need to be ill for their own sake, and some people badly need to be ill to provide important choices for others.
Adoption and contraception, like reading, mathematics, and stress-induced illness, are products of an animal that is living in an environment radically different from the one in which its genes were naturally selected.
He has no theistic beliefs, but shares the poetic naturalism that the cosmos provokes in.
What is the colour of abstraction? What is the smell of hope?
But religious faith is an especially potent silencer of rational calculation, which usually seems to trump all others. This is mostly, I suspect, because of the easy and beguiling promise that death is not the end, and that a martyr’s heaven is especially glorious. But it is also partly because it discourages questioning, by its very nature.
The point about recurrent reproduction life cycles, and hence, by implication, the point about organisms, is that they allow repeated returns to the drawing board during evolutionary time.
The pre-eminent mystery is why anything exists at all.
A DNA molecule in the germ-line of an individual who happens to die young, or who otherwise fails to reproduce, should not be called a dead-end replicator. Such germ-lines are, as it turns out, terminal. They fail in what may metaphorically be called their aspiration to immortality. Differential failure of this kind is what we mean by natural selection.
But whether it succeeds in practice or not, any germ-line replicator is potentially immortal. It ‘aspires’ to immortality but in practice is in danger of failing.