I've meaning to write this for awhile, because this really keeps depressing me. It's the population argument for a young Earth. Specifically, it's the argument that if the world's population is 6 billion, it can't be more than a few thousand years old. Why? Because if people were around longer, there should be lots more people.
You can find this argument on various creationist sites.
This argument is so trivial that it can be refuted with some simple logic and a basic understanding of ecology. Every population has an upper limit imposed on it by limitations of available resources. Living organisms need resources (i.e. food, water) to survive, and if there isn't enough to go around, the population can't grow. In some cases, the population will swing up and down, depending on conditions in the environment.
So clearly there are limitations on the growth of the human population that prevents this all-out growth some creationists insist would have happened. This is simple common sense. Mind you, there is no doubt the human population has experienced rapid growth over the last few hundred years. But this is explained by increasing the available resources through industrialization, as well as improving health and survival via medicine.
What's really depressing about this, however, is the fact that I learned this stuff before getting to high school. This is junior high level stuff at best. Heck, we learned about ecology, population cycles, etc, in primary school. It's so utterly depressing to think that there are creationist arguments being used that could be refuted by someone with a 5th grade eduction.
