Bumble Bee Tuna

Well in BC&A the topic of how humans were allegedly meant to live forever on Earth was brought up.

but Genesis 1:28 has God telling humans to be fruitful and multiply. Now, it seems to me that the command to multiply and the fact that God gave humans genitals to be evidence against the idea of eternal life. If people are supposed to multiply, and they never die, the Earth will fill with people pretty quick and there won't be enough room. Reminds me of the argument I recently heard on fundy radio that evolution can't work because if man has been around for 1000000 years then there would be 10^8000 humans around now (assuming constant growth rate of 2%). The growth rate if nobody ever died would be a lot higher than 2%...

So I'm wondering what theists think about why God would have planned for humans to overpopulate the planet. I guess the question might be, why do we have genitals? Or if sex was deemed necessary, why does it entail reproduction?

-B