Ferguson is a British historian who earned his PhD at Oxford University, and has taught at Oxford, New York University, and Harvard University. He is now a senior fellow at the Hoover Institution, Stanford University. His other books include The House of Rothschild, The Pity of War, Colossus, and Empire. He is a contributor to magazines and newspapers, and has written and presented four documentary series for the BBC’s Channel 4.

Pizarro was a Spanish conquistador who led expeditions to Peru in the 1500s in search of gold and silver. His men fought and defeated the Incas, taking their precious metals. He was killed in 1541, four years before the Spaniards discovered the hill called Cerro Rico, which held great quantities of silver ore. The Incas were forced to mine the ore so that coins could be minted and shipped to Spain.

Fibonacci wrote a book called Liber Abaci(“The Book of Calculation”)in 1202, which was crucial for the development of credit. It introduced Hindu-Arabic numerals and described fractions and decimals, both of which were necessary to calculate interest.