Our species didn’t come into its own until we started living past the age of 30:
Anthropologist Rachel Caspari of Central Michigan University used teeth to identify the ratio of old to young people in Australopithecenes from 3 million to 1.5 million years ago, early Homo species from 2 million to 500,000 years ago, and Neanderthals from 130,000 years ago. Old people – old here means older than 30 (sorry) – were a vanishingly small part of the population. When she looked at modern humans from the Upper Paleolithic, about 30,000 years ago, though, she found the ratio reversed – there were twice as many adults who died after age 30 as those who died young.
The Upper Paleolithic is also when modern humans really started flourishing. That’s one of the times the population boomed and humans created complex art, used symbols, and colonized even inhospitable environments. … [O]nce humans found a way to keep old people around, everything changed. Old people are repositories of information, Caspari says. They know about the natural world, how to handle rare disasters, how to perform complicated skills, who is related to whom, where the food and caves and enemies are. They maintain and build intricate social networks. A lot of skills that allowed humans to take over the world take a lot of time and training to master, and they wouldn’t have been perfected or passed along without old people.
(Photo: The Lady of Brassempouy, dating from the Upper Paleolithic ca. 23,000 B.C.)