<i>humans could use more natural attrition</i><p>What&#x27;s your evidence that more attrition will create a greater society?  If anything, greater longevity of people would allow for the accrual of more knowledge and wisdom.  Living longer gives you a better long-term perspective.  Give people a direct reason to care about what the environment will be like 150 years from now and maybe they&#x27;ll care more about the CO2 they&#x27;re putting out.<p><i>but right now</i><p>None of this is right now.  We&#x27;re right at the infancy of genetic manipulation.  Even with the accelerating rate of technology growth, we won&#x27;t understand our biology at a genetic level enough to be able to manipulate it in an everyday way for at least 50 to 150 years.