Mankind reached its first billion just as the 19th century got underway. That feat of fecundity required eons. It took us just 12 years, however, to tack on the last billion. We're definitely on a roll.
When people shop at the local market and bring home different varieties of apples and peaches and tomatoes, they don't spend too much time thinking about the sex that lay behind those fruits or the development of the different varieties.