They were interested in trade, not caste (chattel) & eunuch slaves, & sub sahara wasn't worth it.
Blame the ming emperor that had the great chinese fleet burned down to a miniscule size & the qing dynasty for not continuing or surpassing the qin, han, song, & half way to the ming dynasty. They could have withstood against the british & the opium the brits brought in designed to destroy chinas economy into dependency towards brit economy. China Could have colonized the world instead & kept their knowledge from being surpassed & reversed engineered with aid from commissioned chinese metallurgist or engineers. They were the richest & most advance of all ancient civilization for 2 millenium due to paper, ink, wood block/movable type printing, silk, porcelain, industrial mass production of cast iron then steel due to the double action piston belows, gun powder, rockets, crossbow, the compass, cosmic engine, armillary sphere & gimballs (gyroscope).
The Gun can be attributed to China's Fire Lance but the constant reinventions, modifications, & improvements done independently & indigenously using indigenous academics, science, math, tech, experiments on the firing mechanism, barrel, projectiles, & the incendiary medium that lunch or propels the projectile, makes it mostly of the culture & society that created its evolution into a flint lock in Europe, then revolvers, repeaters, machine, automatic. Colt, Luger, Maxim, Gatling, Browning, Winchester, Simonov, & Kalashnikov. http://www.youtube.com/watch?v=5KfJ_irbprY&feature=relatedhttp://en.wikipedia.org/wiki/List_of_Chinese_inventionshttp://en.wikipedia.org/wiki/List_of_Indian_inventions_and_discoveries
After the middle ages 1 region (Europe) surpasses The Orient, Anatolia, India, & Asia minor (middle east: Levant, Persian, Egypt) to shape the modern world. With Internal combustion engine (diesel/gas), external combustion engine (steam), AC electric motor, Rubber Tires/Insulation/Gasket, Physics, Calculus, Relativity, Quantum, Air Condition, Type Writer, Sewing Machine, Radio, Television, X-Ray, Nuclear, Iron Ships, Submarines, Turbine: Air Breading mixed Fuel Injected internal combustion engine (Jet engine), Antibiotics, Vaccines. http://en.wikipedia.org/wiki/Invention_of_radio
Issac Newton, George Boole, Robert Boyle, Georg Simon Ohm, Willehord Snellius, Nikola Tesla, Thomas Saint, Charles Goodyear, John Ericsson, Percy LeBaron Spencer, Willis Haviland Carrier, George Westing House, Alexander Graham Bell, James Naismith, Walter Clopton Wingfield, Orville & Wilbur Wright, Thomas Alva Edison, Vladamir Zworykin, Ignacy Luka Siewicz, Igor Sikorsky, Andrei Sakharov, J. Robert Oppenheimer, Edward Teller, Stanislaw Ulam, Johann Zahn, Louis Le Prince, Baron Karl Von Drais, Paul Edward Yost, Konstantin Eduardovich Tsiolkovsky, Sergey Pavlovich Korolyov, Wernher von Braun, Henrich Rudolf Hertz, Karl Ferdinand Braun, Neil Christensen, Alexander Popov, Thomas Newcomen, James Watt, Richard Trevithick, Alexander Flemming, Kalman Tihany, Carlos Glidden, Samuel W. Soul, Charles Darwin, Herbert Akroyd Stuart, Hans Von Ohain, Nikalaus Otto, Karl Benz, Alessandro Volta, Herman Hollerith, Blaise Pascal, Alexander Cummings, John Augustas Roebling, John W. Meaker, Jagadish Chandra Bose, Sir William Hamilton, Albert Einstien, Werner Heisenberg, James Ritty, Sergei Gavrilovich Simonov, Mikhail Kalashnikov, Samuel Colt, Marin Le Bourgeoys, Eduard Rubin, Oliver Winchester, Georg Luger, Hiram Maxim, John Browning, Richard J. Gatling, Solymon Merrick, Dimitri Mendeleev, Benjamin Holt, Nicolas Apert, James L. Kraft, Arthur James Arnot, Stephanie Kwolek, Dean Kamen, Jack Kilby, Robert Noyce, Clayton Jacobson, Chester Carlson, Steve Jobs, Dr. Martin Cooper, Johannes Gutenberg (not the first, but independent from Bi Sheng).
Ancient Mysteries: Dragon's Ascent, Forging the Future, Feast or Famine, Two Way Traffic, History as a Mirror, China's Wall of Doom, Reincarnation: Samurai, Lost Spirits of Cambodia.
Where Did It Come From? Ancient China: Masters of the Wind, Personal Weapon, Agriculture, Origins of Drilling & Mining.
Ancient Discovery: Ancient Chinese Superships, Deat Weapons of the East, Chinese Warfare, Machines III.
Mughal: Warrior Empire
In search of History: China's Forbidden City, Tibet's Lost Paradise: Shangrila, Forgotten city of the Jungle, Samurai Warriors.
Investigating History: Genghis Khan, Genghis Khan Terror & Conquest.
History's Mysteries: The True Story of Marco Polo: Human Bondage
Biography: Marcopolo Journey to the East, Confusious Words of Wisdom