My theory is that two people who each live to 40 will together experience more joy than one person who lives to 80. I remember the first time my daughter tasted chocolate. I could get filthy rich and buy a yacht and I don&#x27;t think I could feel joy like that as an adult. If we maintain population at equilibrium, people living twice as long will mean half as many kids born each year. Half as many first tastes of chocolate. Life extension carries with it an enormous opportunity cost.