Welcome to the forum! I am glad that you posted this! And also I disagree with much of it. Carl Shulman already responded explaining why he things the extinction rate approaches zero fairly soon, reasoning I agree with.
Under a stable future population, where people produce (on average) only enough offspring to replace themselves, a person’s expected number of descendants is equal to the expected length of human existence, divided by the average lifespan (l). I estimate this figure is 93[22].
To be consistent, when comparing lives saved in present day interventions with (expected) lives saved from reduced existential risk, present day lives saved should be multiplied by this constant, to account for the longtermist implications of saving each person. This suggests priorities such as global health and development may be undervalued at present.
I think the assumption about a stable future population is inconsistent with your calculation of the value of the average life. I think of two different possible worlds:
World 1: People have exactly enough children to replace themselves, regardless of the size of the population. The population is 7 billion in the first generation; a billion extra (not being accounted for in the ~2.1 kids per couple replacement rate) people die before being able to reproduce. The population then goes on to be 6 billion for the rest of the time until humanity perishes. Each person who died cost humanity 93 future people, making their death much worse than without this consideration.
World 2: People have more children than replace themselves, up to the point where the population hits the carrying capacity (say it’s 7 billion). The population is 7 billion in the first generation; a billion extra (not being accounted for in the ~2.1 kids per couple replacement rate) people die before being able to reproduce. The population then goes on to be 6 billion for one generation, but the people in that generation realize that they can have more than 2.1 kids. Maybe they have 2.2 kids, and each successive generation does this until the population is back to 7 billion (the amount of time this takes depends on numbers, but shouldn’t be more than a couple generations).
World 2 seems much more realistic to me. While in World 1, each death cost the universe 1 life and 93 potential lives, in World 2 each death cost the universe something like 1 life and 0-2 potential lives.
It seems like using an average number of descendants isn’t the important factor if we live in a world like World 2 because as long as the population isn’t too small, it will be able to jumpstart the future population again. Thus follows the belief that (100% of people dying vs. 99% of people dying) is a greater difference than (0% of people dying vs. 99% of people dying). Assuming 1% of people would be able to eventually grow the population back.
Welcome to the forum! I am glad that you posted this! And also I disagree with much of it. Carl Shulman already responded explaining why he things the extinction rate approaches zero fairly soon, reasoning I agree with.
I think the assumption about a stable future population is inconsistent with your calculation of the value of the average life. I think of two different possible worlds:
World 1: People have exactly enough children to replace themselves, regardless of the size of the population. The population is 7 billion in the first generation; a billion extra (not being accounted for in the ~2.1 kids per couple replacement rate) people die before being able to reproduce. The population then goes on to be 6 billion for the rest of the time until humanity perishes. Each person who died cost humanity 93 future people, making their death much worse than without this consideration.
World 2: People have more children than replace themselves, up to the point where the population hits the carrying capacity (say it’s 7 billion). The population is 7 billion in the first generation; a billion extra (not being accounted for in the ~2.1 kids per couple replacement rate) people die before being able to reproduce. The population then goes on to be 6 billion for one generation, but the people in that generation realize that they can have more than 2.1 kids. Maybe they have 2.2 kids, and each successive generation does this until the population is back to 7 billion (the amount of time this takes depends on numbers, but shouldn’t be more than a couple generations).
World 2 seems much more realistic to me. While in World 1, each death cost the universe 1 life and 93 potential lives, in World 2 each death cost the universe something like 1 life and 0-2 potential lives.
It seems like using an average number of descendants isn’t the important factor if we live in a world like World 2 because as long as the population isn’t too small, it will be able to jumpstart the future population again. Thus follows the belief that (100% of people dying vs. 99% of people dying) is a greater difference than (0% of people dying vs. 99% of people dying). Assuming 1% of people would be able to eventually grow the population back.