Population and Migration.

Thomas Malthus didn't think that people could start producing food quicker and quick enough to feed the many people, or growing population. This happened with high-yield crop varieties, aftificial fertilizer and pesticides, and a ton of technology, and more. (Second and Third Agricultural Revolution). There are now tractors, and all that. And we can produce more food on less land.

Thomas Malthus said food grows geometrically, while the population grows exponentially.