Our primate progenitors had bodies a lot like those of modern monkeys and spent tens of millions of years living in trees. From them we inherited our versatile hands, amazing vision and capable brains — but also some less beneficial traits, including our bad backs and terrible sense of smell. YOUR INNER FISH “Episode 3” premieres Wednesday, April 23 at 10/9c following NATURE at 8/7c and NOVA at 9/8c as part of PBS’ THINK WEDNESDAY.