3 ms·

I'm not going to touch the right/left stuff, just want to jump in on the variety/evolution thing. The "killing off parts of that variety" is a mechanic that is

I'm not going to touch the right/left stuff, just want to jump in on the variety/evolution thing. The "killing off parts of that variety" is a mechanic that is not universally accepted; genetic drift has been documented to happen for non-red-in-tooth-and-claw situations. That's not to say it's discredited or anything, but it's just one mechanism. The thing shared by all mechanics of evolution is that they need a population with enough internal variation to be able to move the needle at all. A population that needs to evolve itself out of a corner (say a dramatic change in environment) needs time in proportion to variety, not in proportion to mutation rate. And no population survives without producing almost entirely viable offspring. We did not practice eugenics on dogs for millenia -- we selectively bred dogs. We bred different breeds for different purposes, and the more narrow the breed is, the less robust it is (I don't think anyone would question this if they had ever read anything about pedigreed breeds). The reason why dogs are robust as a species is largely because we didn't focus on one particular trait across the entire species, so with cross-breeding (and even breeding with wild dog-like animals) we can retain some level of robustness.

Udik 6y ago
> The thing shared by all mechanics of evolution is that they need a population with enough internal variation to be able to move the needle at all. A population that needs to evolve itself out of a corner... True. In a sense, your metaphor of variation as the fuel of evolution is very apt. Variation is indeed the fuel of evolution, in the sense that evolution consumes it. In order to make your car move, you need the fuel and you need to consume it. When "a population evolves itself out of a corner" it does so by consuming part of its variation. The population survives, the single individuals might be selected out (or single traits, through differential reproduction rates). > We did not practice eugenics on dogs for millenia -- we selectively bred dogs. It seems to me that any form of selective breeding when applied to human beings falls entirely into the definition of eugenics. The Merriam Webster defines eugenics as: "the practice or advocacy of controlled selective breeding of human populations (as by sterilization) to improve the population's genetic composition". > the more narrow the breed is, the less robust it is Absolutely true, but dog breeds are (especially in recent times) are really extreme and cruel forms of selection. Commercial breeders (and their customers) are following absurdly strict appearance canons. On the other hand, the slightest form of imposed human breeding, however transversal to the bulk of human variation (say, for example, discouraging from reproducing people who are more than 2 standard deviations taller than the rest of their country average or reference ethnicity) is already an ethically unacceptable form of eugenics, independently from its practical impact on the genetic variation of humanity.

Udik 6y ago

> The thing shared by all mechanics of evolution is that they need a population with enough internal variation to be able to move the needle at all. A population that needs to evolve itself out of a corner... True. In a sense, your metaphor of variation as the fuel of evolution is very apt. Variation is indeed the fuel of evolution, in the sense that evolution consumes it. In order to make your car move, you need the fuel and you need to consume it. When "a population evolves itself out of a corner" it does so by consuming part of its variation. The population survives, the single individuals might be selected out (or single traits, through differential reproduction rates). > We did not practice eugenics on dogs for millenia -- we selectively bred dogs. It seems to me that any form of selective breeding when applied to human beings falls entirely into the definition of eugenics. The Merriam Webster defines eugenics as: "the practice or advocacy of controlled selective breeding of human populations (as by sterilization) to improve the population's genetic composition". > the more narrow the breed is, the less robust it is Absolutely true, but dog breeds are (especially in recent times) are really extreme and cruel forms of selection. Commercial breeders (and their customers) are following absurdly strict appearance canons. On the other hand, the slightest form of imposed human breeding, however transversal to the bulk of human variation (say, for example, discouraging from reproducing people who are more than 2 standard deviations taller than the rest of their country average or reference ethnicity) is already an ethically unacceptable form of eugenics, independently from its practical impact on the genetic variation of humanity.