>There is a test tube with a microbe on the bottom.
>It looks around and decides to breed. Soon there
>are two microbes. A few days later there are four
>microbes. A small microbe society begins to form.
>After a day or two the test tube is ten percent
>full and it's microbe heaven. Then twenty and then
>forty and fifty percent. Life for the microbes is
>good. With the tube fifty percent full they look
>around and see lots of room for expansion. Unfortunately,
>they haven't paid too much attention to the fact that
>their species has expanded at almost an exponential
>pace and they are at fifty percent. The next time they
>breed they'll be swimming in their own poop as they die.
>Well, folks the test tube is the earth and we are the
>microbes and we are at about fifty percent planet occupation.
>What will we do?

The trouble with us, unlike microbes, penis-ill-in propagates us rather than destroying us.