Well, as has been discussed to death on many sites/threads regarding half-elf/Ancient Elf, Paizo has made a 'heritage' (something to be obtained at birth through something akin to a genetics) related to old age. It just doesn't make any sense.
Why do you equate "heritage" with "something to be obtained by birth"? It just as much reflects cultural upbringing or long years of practice before going out to adventure. Similar to how the backgrounds reflect experience in non-adventuring professions or occupations. Many heritages are inherited, but some are obviously not, like the wildwood halfling, who has just practiced running trough the rough woods so much that it's no longer difficult for him, or the cavern elf, whose darkvision can be either inherited or acquired through long years of living underground. Or the oathkeeper dwarf, where it's really more of a character trait likely fostered by a lawful culture. The ancient elf fits right in, having acquired much more extensive experience than others over many centuries of life.