At the beginning the 19th century during the rosy dawn hours of the Industrial Revolution the world’s human population finally surpassed 1 billion individuals.  After about 200,000 years of evolution our extraordinary intellect and extreme mobility had brought us that far. We had, by then, colonized every continent except Antarctica. Civilized cultures were generally aware of the world as a finite sphere, 70 percent of it covered in water. We lived everywhere, from the sweltering tropics to the icy arctic wastelands.
We dominated everything we surveyed, but we couldn’t survey the microscopic yet, at least not very effectively. The germs still pretty much had their way with us. They limited human population growth. Average Europeans were lucky to live to 40 years of age. Almost a third of babies born in Europe’s cities died before their third birthdays, mostly due to diseases borne by microbes. People flocked to the cities where they found new affluence in factories and textile mills. The crowding in city tenements gave the pathogens an ideal habitat and accelerated the spread of disease.
Louis Pasteur was born in 1822 and soon began whipping the germs into shape. With an uncanny instinct for the nature of disease, Pasteur revolutionized our understanding of the world and helped us train new weapons on the microbes that made us sick. Pasteur gave us the specific tools to fight cholera, anthrax and rabies, but more importantly he revolutionized our knowledge of microbes and their effect on our lives – both good and bad. We had been drinking wine for thousands of years but we didn’t know that bacteria caused fermentation. Pasteur identified disease-causing germs and invented tools for fighting them. Soon, people were living longer. More babies survived. Modern medicine was born, and human population growth accelerated.
By 1900 there were more than 1.6 billion of us, up 60 percent in one century. That population doubled in about 60 years, then doubled again in half the time. I was born into a worldwide human population of about 3 billion people. Based on current United Nations projections and my expected lifespan, there will probably be about 9 billion people on earth when I die.
So far we’ve done a remarkably good job of feeding all these new people. When you think about it, it’s almost miraculous that we’ve kept up with our own expansion. Shortly before Louis Pasteur was born, the English philosopher Thomas Robert Malthus made himself one of the world’s most famous thinkers by suggesting that unless we did something about population growth, we could never ease the burden of poverty. His basic thesis was that because our population expanded geometrically while food production expanded arithmetically, and because birth rates increase with prosperity, we would never be able to create consistent surpluses in food supply.
The poor, as Jesus of Nazareth said, would “always be with us.”
 The World at Six Billion, United Nations Population Division.
 Debré, P.; E. Forster (1998). Louis Pasteur. Baltimore, MD: Johns Hopkins University Press. ISBN 0-8018-5808-9.
 New Testament, Book of Matthew, Chapter 26, Verse 11.