The scientists in the timeline and their contributions:

• 1785: James Hutton proposes that slow-acting geological forces shape the planet. He estimates Earth to be millions—not thousands—of years old.
• 1798: Thomas Malthus in his Essay on the Principle of Population predicts that left unchecked, the human population will grow beyond the space and food needed to sustain it.
• 1809: Jean Bapptise Lamarck publishes his hypotheses of the inheritance of acquired traits. The ideas are flawed, but he is one of the first to propose a mechanism explaining how organisms change over time.
• 1831: Charles Darwin sets sail on the HMS Beagle, a voyage that will provide him with vast amounts of evidence to support his explanation of how evolution works.
• 1830-33: Charles Lyell - In his Principles of Geology, Lyell explains that over long periods, the same processes affecting Earth today have shaped Earth’s ancient geological features.
• 1858: Alfred Russell Wallace writes to Darwin, speculating on evolution by natural selection, based on his studies of the distribution of plants and animals.
• 1859: Darwin publishes On the Origin of Species.