There is a great podcast by Stephen Fry, he suggests it's because we are able to store knowledge and share it without needing to be in the same place, i.e writi

There is a great podcast by Stephen Fry, he suggests it's because we are able to store knowledge and share it without needing to be in the same place, i.e writing and other forms of documenting culture, that humans have shot so much further in terms of shared intelligence. http://www.stephenfry.com/greatleapyears/ http://www.stephenfry.com/greatleapyears/