Ramez Naam discusses the reason why ideas catch on and spread in this evolving ideas speech. Naam talks about how useful ideas stick with people and evolve overtime, using the wheel as an example. Some ideas die off after a while because they aren't innovative enough, while others catch on and thrive.
Naam also discusses ideas that help to accelerate the spread of other ideas, such as the printing press or the Internet. People use media to provide others with information on one project or another, which also helps ideas to catch on.
Ramez Naam talks about the way in which some good ideas keep evolving while others fade away, having failed the Darwinian evolution test. With all of the technology and information available at people's fingertips, it's easy for anyone to share their ideas with the world, which contributes to the overall evolution of ideas.