(video, 16 min)
Matt Ridley, the author of The Rational Optimist and many other great books, argues that humanity's collective brain created through trading and exchange of ideas is what makes us different from other species.
This simple idea is much deeper than it may appear at first glance.
According to Matt Ridley, over the course of a million+ years, humans started producing more tools that cannot be made by any single person, but require collective intelligence of a (large) number of people. For example, take two objects of similar size: a hand axe, made essentially without additional innovations for 1 million years, and a computer mouse.
A hand axe can be made by a single person. But no single person knows how to make a computer mouse from raw materials. Sure, an assembly worker may know how to put it together from pre-made parts. But does any one person know how to do this, and how to make plastic for the mouse parts, and how to drill and refine the oil to make the plastic, and how to make the laser for the mouse, and how to mine metal ore, and how to produce metal parts for the mouse, etc?
What makes humans different from other species is that we use trade. There is a great illustration of why trade makes sense even for people who are more productive than others at any given task. Trade is for ideas in technological innovation what sexual reproduction is for genes in biological evolution. It allows for mixing and matching the winning ideas. For example, for the computer mouse you need the idea of plastic and laser to meet and "mate".
When trade is interrupted for long periods of time, humans regress in their innovation path. For example, people who lived in Tasmania lost their ability to make bone tools, fishing equipment and clothing after the rise of sea levels 10,000 years ago separated them from Australia, and Tasmania became an island isolated in terms of trade.
Matt Ridley argues that it is the trade, the sexual reproduction of ideas, the creation of a "collective brain" that is a major contributor to the rapid progress of humanity even as the population grows. How rapid is the progress? Take one example. Today in a developed country, a person on an average wage has to work for 0.5 seconds to earn enough to buy 1 hour of light suitable to read a book (fluorescent light). Back in 1800s, you had to work for 6 hours to earn enough to buy a candle to provide 1 hour of reading light.
For a longer version of a similar talk, see The Rational Optimist: How Prosperity Evolves - book forum at the Cato Institute.
(80 min video, but it is the audio that makes it interesting)
That version has a commentary by Robin Hanson and a Q&A session. Interestingly, Ridley's ideas are received well by (read: mated with!) both the liberal TED and the conservative (libertarian) Cato Institute.