The act of one human speaking to a group has evolved over hundreds of thousands of years.
Books For Africa has sent more than 41 million books over the last 30 years.
Expect a contentious G7 amid Trump's escalating trade battle
In feud over immigration, House GOP scrambles for a deal
Bill Clinton: Monica Lewinsky 'paid quite a price' for relationship
Brennan: Trump threatened by law enforcement because they can expose his falsehoods
Economics correspondent Paul Solman reports on the impacts of bitcoin mining.