I think you make some good observations, but I'd wager if you think these statements through a while longer, you'll adjust your position. Jaan (a single high fitness human) having multiple children doesn't connect directly to the real issue of overpopulation. The carrying capacity of the earth (with efficient use of vertical space) is orders of magnitude large than our current population. Survival-necessary resources are not scarce. Depletion of scarce resources causes serious economic and societal impact, but can you name one irreplaceable scarce resource? We're almost out of oil but tech will transition to alternatives soon. I worry about byproducts of overpopulation, like multiple antibiotic resistance bacteria and calcified local optima in social systems.