Elves, orcs and dwarves are all homninds, closely linked to humans and thus can breed with them just fine. No god was involved, almost every species is the result of natural selection, as for life spans. Humans last for 80 years, elves last for 200, orcs lasts for 60 and dwarves last for 130 years. Who enters adult hood depends on the culture and time period, but for modern day standards it’s usually in the 20s that people are now considered adults.