What prevents evolution?

[arahant]

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Without a specific mechanism stopping it, the opposite is also true. The problem of the intra-species exception is unresolved. You have not accounted for the discrepancy between the respective tendencies within and without species toward reproductive incompatibility. If you think you have done so and I have missed it, perhaps you can reiterate in a concise form.

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The mechanism that stops it is the need to reproduce with members of one's population, and ONLY that population. Individuals in a population all change; those changes that are compatible with each other are reproduced. That is, it MATTERS that I can mate with somebody who lives next to me. It DOESN'T matter if I can mate with someone in india.

Was my prior example unclear? Or are you just focusing on the statements that you find to be most ambiguous?