I think you are misunderstanding how natural selection works. You seem to be implying that there is some guiding hand behind the evolution of each species. In

I think you are misunderstanding how natural selection works. You seem to be implying that there is some guiding hand behind the evolution of each species. In fact, if longer life were an advantage for an individual member of any species, the gene pool would gradually shift towards longer life. Some species do indeed have extremely long lives-- some trees live for thousands of years, and some whales and turtles can live and even reproduce for more than a hundred years. Instead, life length is a tradeoff that is made at the individual level. A longer life means more opportunities to reproduce (or help your offspring), but it also means that you have to set a higher limit for the number of divisions each cell can make, which can decrease cancer resistance. A slower metabolism will produce fewer harmful byproducts, but give you less energy than a fast-burning metabolism. And so on. Longer life makes more sense for more intelligent organisms, since they can be more effective when they're older due to what they have learned. Often, they need teach the young, which can have relatively long gestation times. But an organism's lifespan is always going to be oriented around its reproductive cycle. With all that being said, humans are very clever and I wouldn't be surprised if ways were found around human mortality eventually. I can't help thinking of all the "humans were never meant to fly" arguments that people used to pooh-pooh heavier than air flight in the old days. There's no fundamental reason why life extension couldn't be done except time and effort. But I am not as optimistic as Kurzweil about the timeframe (who is?)