For that to work, they don't have to be ancient. Just fit enough long enough to be too much of a net burden to the younger generations. The menopause seems to c

For that to work, they don't have to be ancient. Just fit enough long enough to be too much of a net burden to the younger generations. The menopause seems to coincide with the age where people used to become grandparents. Furthermore, people getting too old might make it harder for collective cultural knowledge to evolve. Which is fine in good times, but disadvantageous in volatile circumstances.