on species

I've been wondering as I look at the world if species, like individuals, go through the stages of growth sort of like the seven roles of man that Shakespeare listed? We know, for instance, that although the dinosaurs lasted for millions of years as a group, the individual species changed and developed and died out. Are the present species of this earth of ours doing the same thing? We've seen species that have died out for one reason or another: climate changes, they begin to decline and humans killed them off (mammoths and giant sloths), they were superseded by environmental conditions such as the increase in forests in Ireland that destroyed the huge antlered red deer of that island. I wonder, however, if species don't start out young and lively, become more sedate in a kind of middle age and then slowly fade out into the sunset like the sabre toothed tiger and the dire wolf. If that does happen, what does it mean for us? I sometimes think that we humans as a species are in either late childhood or early adolescence with not fully developed inhibiting centers in our brains. It would explain our need for gods (parents) and our inability to get along on the playground.