All of FeelingSentient's Comments + Replies
2. I'm not sure I understand your last point. Even if a small change pushes the barely tolerable to intolerable you still have the opposite effect on the other side of the curve, where it provides relief. I am assuming here that in most polygenic traits the curve is not so narrow that there aren't dysfunctional individuals being produced on both extremes.
3. I concede your point that if there is less than perfect competition, this effect doesn't completely negate any effect on average welfare. It would still make such an effect smaller and less relevant as compared to other considerations, like species composition.
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2. tl;dr: The effect would be smaller on the opposite side, assuming something like a normal distribution of temperatures at baseline and a symmetric survival rate (or serious adverse event) function of temperature, centered on the mean temperature, which we would assume by symmetry, and because of the optimization of evolution. So, the animals who benefit would benefit less than the harm to the animals who are made worse off. You'll get more deaths on the side you're moving the temperature towards than you're preventing on the other side.
Assume the survival rate function is unimodal and increasing/nondecreasing to the left of its mean/max and decreasing/nonincreasing to the right of its mean/max, so basically has a shape similar to a normal distribution.
To illustrate with a simplified example, assume the temperature is just constant, and we're just shifting this constant temperature. The survival rate will be lower anywhere away from the mean, and lower the further away from the mean. We're assuming at equilibrium, the temperature already maximizes this, and so any shift in temperature, in either direction, will decrease survival.
Survival rate function of temperature, centered at the mean temperature
The same would happen for a uniform distribution of temperatures within some bounded range, initially centered at the centre of the survival function distribution, and shifting the whole temperature distribution. The expected survival rate, i.e. taking the expected value of the survival rate as a function of temperature over the temperature distribution, would be lower if you shift the temperature distribution in any direction. This would basically just be the area under the curve where the temperature distribution is, and this is maximized if the temperature range, holding its width constant, has the same mean/centre as the survival rate function. Intuitively, you could just replace the sharp constant temperature distribution with a very narrow uniform distribu
I regret not having numbered my points above :P
2.
A change in either direction will put the average away from what the individuals are best adapted to on average and under a symmetric assumption (like approximate normality), I'd expect it to hurt more individuals than it helps.
Suppose a human in a t-shirt and jeans, going for a walk. Preferred temperature: 24 °C. The weather turns and the temperature drops to 14 °C. Is this person half as physiologically stressed and half as miserable as they would have been if the temperature had dropped to 4 °...
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Welfare gains and losses could be mostly driven by the extremes, I don't know. But animals already live in environments with variable temperatures, some of which may be intolerable or barely tolerable. A small average change can push the barely tolerable to intolerable. And this will happen more on the extreme the average temperature is heading towards.
I think I get your 3rd point now. If we're using something like average fitness as a correlate of average welfare, and different species are competing, then a change that's bad on average for one species would be good on average for its competitors, and we can't say whether the change tends to be more good or bad overall using an a priori argument like mine. Competition basically prevents the changes from being random in the way my argument assumed. However, this just gets you symmetry again under uncertainty.
Maybe you can zoom out and consider the average fitness in the whole multi-species population in a given ecosystem. And not all changes need involve significant competition between species, so for the ones that don't, symmetry is broken again in favour of a negative effect on average welfare, which in turn would break symmetry in favour of a negative effect overall.
Some objections:
- you're conflating fitness and welfare. Counterexample: a high resources high predator environment were being super paranoid and stressed out all the time gives you high fitness and poor welfare.
- most traits are polygenic and, therefore, normal-ish. Changes in the environment (e.g. higher temperature) increase fitness on one end of the distribution (e.g. the more heat tolerant individuals are doing great) while decreasing it in the other (e.g. the less heat tolerant are doing badly). What are the total welfare implications of that?
- you'r
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Thanks for the comment!
I think this is fair, but I still expect the correlation to usually be positive and my argument is only probabilistic and a priori, anyway.
In this example, you're shifting the mean temperature, and I think a given species will be best off in the short-run with the mean temperature they're adapted to. A change in either direction will put the average away from what the individuals are best adapted to on average and under a symmetric assumption (like approximate normality), I'd expect it to hurt more individuals than it helps. So, for average welfare, there's more reason to think it's bad than good and the expected value is negative.
I didn't assume this, and the general structure of my argument seems as strong whether you include other interacting species or not; they're just part of the environment and conditions under consideration. However, I did invoke symmetry assumptions a lot, which I'd be more reluctant to apply in any specific case about which I'd have more information, and would instead have complex cluelessness.
Good point. Something I've been thinking about lately is that shorter and larger generations (which I'd expect to have lower average welfare due to higher mortality and lower investment per offspring) and r-selected species would be favoured by this, though, which also seems bad for average welfare.
On the other hand, small enough changes might lead to antifragility and be good for average welfare.
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