Why are humans the only species with advanced intelligence?

Dr Chris answers more listener questions, including: How do sunflowers follow the sun? How does the body determine when you're passing wind or something more solid? Why are mosquitos attracted to some people more than others? Why are some people more intelligent than others? Why are humans the only species with advanced intelligence? How intelligent is an octopus? Like this podcast? Please help us by supporting the Naked Scientists (thenakedscientists.com/donate)