text: * 1767 – Kaspar Friedrich Wolff argued that the tissues of a developing chick form from nothing and are not simply elaborations of already-present structures in the egg.
  * 1768 – Lazzaro Spallanzani again disproved spontaneous generation by showing that no organisms grow in a rich broth if it is first heated (to kill any organisms) and allowed to cool in a stoppered flask.  He also showed that fertilization in mammals requires an egg and semen.
  * 1771 – Joseph Priestley demonstrated that plants produce a gas that animals and flames consume. This gas was oxygen.
  * 1798 – Thomas Malthus discussed human population growth and food production in An Essay on the Principle of Population.