I heard an author (wish I could remember his name) on the radio promoting his new book. In his book he talks about scientific advancements being made, like one group is making a wooly mammoth in a lab. He specifically clarified, they are making it, not cloning it. He said they are writing DNA. He predicted the generation being born now will live 150 - 180 years. The next generation may never die. Think this rock is getting crowded now? Give it another 75 years.