Jean-Baptiste Lamarck believed that physical diversity among animals could be explained by physical stressors experienced by one generation being passed on to the next. Giraffes, therefore, have long necks because one giraffe, a long time ago, had to stretch out and reach for food, and this characteristic was passed on to its offspring.
What are the problems with Lamarckâ€™s theory of evolution?
For centuries, astronomers could not explain the strange path by which the planet Mercury orbited the sun. Urbain Jean Joseph Le Verrier theorized in 1859 that Mercuryâ€™s strange orbit was the result of another planet interfering with the gravitational pull of the sun. Le Verrier named this other planet Vulcan.
Research the history of Vulcan to explain how its existence was tested and finally disproved.