If the average number of babies per woman continues to be what it is, there will be a lot of competing for space and resources causing suffering. The amount of available energy will not match the energy demands and so many people will be living in an uncomfortably cold house. China is already doing that with the one child policy so why can't other countries with a rapid population growth do the same? If the technology to live for ever gets invented, we need to eventually start having an average of fewer than 2 babies per woman to not run out of space for those people who want to keep on living.