https://phys.org/news/2018-07-genes-weirder-thought.html

Charles Darwin took inspiration from this process, substituting "natural" for artificial (human-determined) selection to shape populations, eventually generating new species (Darwin, 1859). Underlying such evolutionary processes was the presumption that traits, and their variation, was "encoded" in some type of "factors", eventually known as genes and their variants, alleles. Genes influenced the organism's molecular, cellular, and developmental systems, but the nature of these inheritable factors and the molecular trait building machines active in living systems was more or less completely obscure.

Through his studies on peas, Gregor Mendel was the first to clearly identify some of the rules for the behavior of these inheritable factors using highly stereotyped, and essentially discontinuous traits – a pea was either yellow or green, wrinkled or smooth. Such traits, while they exist in other organisms, are in fact rare – an example of how the scientific exploration of exceptional situations can help understand general processes, but the downside is the promulgation of the idea that genes and traits are somehow discontinuous – that a trait is yes/no, displayed by an organism or not – in contrast to the realities that the link between the two is complex, a reality rarely directly addressed (apparently) in most introductory genetics courses. Understanding such processes is critical to appreciating the fact that genetics is often not destiny, but rather alterations in probabilities (see Cooper et al., 2013). Without such an more nuanced and realistic understanding, it can be difficult to make sense of genetic information.