It took over two hundred thousand years of modern human history and 6 million years of human evolution for the world's population to reach 1 billion in 1804; world population reached an estimated 2 billion in 1927; by late 1999, the global population reached 6 billion, with over half in East, South and Southeast Asia. Global literacy averaged 80%. Penicillin and other medical breakthroughs combined with the World Health Organization's global campaigns to eradicate smallpox and other diseases responsible for more human deaths than all wars and natural disasters combined yielded unprecedented results; smallpox now only existed in labs. Machines came to be used in all areas of production, feeding increasingly intricate supply chains that allowed mankind for the first time to be constrained not by how much it could produce, but by peoples' willingness to consume. Trade improvements greatly expanded upon the limited set of food-producing techniques used since the Neolithic period, multiplying the diversity of foods available and boosting the quality of human nutrition. Until the early 19th century, life expectancy from birth was about thirty in most populations; global lifespan-averages exceeded 40 years for the first time in history, with over half achieving 70 or more years (three decades "longer" than a century earlier).