Episode Three: Connecting the World The world is linked like never before. Modern transport and communications have resulted in a world that is wealthier, healthier, more mobile and better informed than ever before. Throughout history new trade routes have proved to be double-edged swords, opening the way to wealth as well as terrible dangers - among them revolutionary ideas and terrifying pandemics. In their quest for silver, the Romans lay down roads across Britain. They have built a giant empire, spanning three continents, building roads to facilitate troop movements, tax collection and, crucially, trade. This vast road network means travel in Europe, the Middle East, and North Africa is safe for the first time. The Christian messenger Paul uses Rome's roads to carry the message of a sworn enemy of the Roman state. He's spreading the word of a religious rebel, Jesus Christ. The Christians take advantage of Rome's infrastructure to spread their message. But another Roman trade route allows a far more sinister threat to travel back: disease. Around 300AD Roman explorers reach the capital of China. Rome's desire for silk has linked East and West for the first time. For over a thousand years after the Romans visited China, the world is struck by wave-upon-wave of pandemics. Smallpox, plague, measles all spread, killing millions. In the Age of Discovery, Europeans travel to the New World carrying guns and something even more powerful: a deadly cocktail of diseases, to which they themselves are immune. Spanish soldiers under the command of Hernan Cortes enter the Aztec capital Tenochtitlan. They unwittingly transmit smallpox and flu to their hosts. 95% of them die. The great Aztec and Inca empires collapse, and Europeans take control of the Americas and their wealth. European settlers in the New World establish giant plantations farming sugar, cotton and tobacco. But the Europeans diseases have decimated the Native American population. There are not enough people to work the land. The settlers' solution is to import slave labour. But the North and South clash over the freeing of slaves. Slavery ends up tearing North America apart. It leads to The American Civil War. However, global trading networks allow millions of immigrants from across the world to pour into America. This hungry new workforce turns America into a superpower. The age of mass migration has begun. It creates new connections, and a demand for fast, mass travel to and from all parts of the globe.