The Chinese began using gunpowder guns before the Europeans
History should not be considered in a linear fashion. Discoveries are often made in different areas at different times. Take for example, the use of gunpowder-powered weapons. They were used much earlier in some parts of Asia than in Europe.
While in 14th century Europe, the French and the English were testing out the latest crossbow technology in the Battle of Crecy, the Chinese were already producing bronze guns that relied on gunpowder. The earliest example found of one dates back to 1332, during the early Yuan Dynasty.