In the 1850s, back when fruit flies were just pests and inheritance of traits a mystery, a monk in the part of the then-Austrian Empire that is now the Czech Republic began systematically breeding pea plants in the abbey garden. Eventually able to define “laws of inheritance” (which you now learn in high school biology class), he had taken the long-understood selective breeding of plants and livestock that had created human civilization as we know it and made it into a science. His research was ignored and the birth of the new field was delayed by a few more decades.
Meanwhile, Charles Darwin explained his theory of evolution by means of natural selection, but was hindered by a certain lack of quantified data. Mendel’s law were rediscovered independently towards the turn of the twentieth century, followed by the rediscovery by the scientific community of his work itself in 1900. A whole new world was opened up and research in the field exploded. Between roughly 1902 and 1904, Theodor Boveri and Walter Sutton each independently proposed chromosomes as the vehicles of inheritance. In 1915, after years of hanging out with fruit flies in his (in)famous (to biology students) Fly Room, Thomas Hunt Morgan, then at Columbia University, gave evidence for the presence of genes on chromosomes, making Mendel’s abstractions physical and real.
We’re still working on taking our understanding, applying it to our observations of the world, and gaining new understanding as a result—the cyclical process that makes me love biology as much as I do. Biology, and other basic natural sciences at their core, is really just the study of what is there. Of creating understanding and then bringing that understanding down to earth. We’re still working on it—and presumably (and hopefully) always will be.