171 Essays on Infinite Lifespans   Max More IT IS HOW MANY, NOT HOW LONG, THAT MATTERS? Limiting  population  growth  by  opposing  life  extension not only fails the ethical test, it also fails the pragmatic test. Keeping the death rate up simply is not an effective way of slowing population growth. Population growth depends far more on how many children families have, as opposed to how long people live. In mathematical terms, longer life has no effect on the exponential growth rate. It only affects a con- stant of the equation. This means that it matters little how long we live after we have reproduced. Compare two societies: In country A, people live on average only to 40 years of age, each family producing 5 children. In country B, the life span is 90 years but couples have 4 children. Despite the much longer life span in country B, their population growth rate will be much lower than that of country A. It makes little difference over the long term how many years people live after they have had children. The population growth rate is determined by how many children we have, not how long we live. Even the short-term upward effect on population due to a falling death rate may be cancelled by a delay in child bear- ing.  Many  women  in  developed  countries  choose  to  bear children by their early 30’s because the obstacles to success- ful pregnancy grow as they age. As the last few decades have already shown, extending the fertile period of women’s lives would allow them to put off having children until later, until they have developed their careers. Not only will couples have children  later,  we  can  expect  them  to  be  better  positioned financially and psychologically to care for them. Almost  certainly,  the  first  truly  effective  technologies  to extend the maximum human life span will come with a sig- nificant  cost  of  human  development  and  application.  As  a consequence population effects would first be felt in the devel- oped countries. This points to another flaw in the suggestion