1854, St. Thomas Monastery, Brno, Czechia
While cross-breeding pea plants, a monk named Gregor Mendel observed something he couldn't explain: Traits sometimes re-emerged after years of absence in a family line. For example, a plant with white flowers could sometimes emerge from a family that had expressed only purple flowers for generations.
Mendel guessed that parents pass segregated “hereditary units” to their offspring, and that expressed traits depend on the dominance or recessiveness of those invisible units.
Mendel did his best to circulate his work, but his contemporaries generally ignored his abstract theory.
1909, Cambridge, United Kingdom
By the early 1900s, scientists began isolating inheritance patterns identical to Mendel’s. They found that offspring often look different from both parents and concluded, as Mendel had before, that living things carry codes for many traits, even those they do not express.
In 1909, 25 years after Mendel’s death, Danish botanist Wilhelm Johannsen named invisible units of heredity "genes." In that same year, English biologist William Bateson used Mendel’s principles as the foundation for a new field of study called “genetics.”
Mendel’s work even found a place in Charles Darwin’s theory of evolution.
Prior to the renaissance of Mendel’s work, the blending inheritance theory had left a mechanistic gap in natural selection. No one could explain how adaptations could benefit multiple generations if favorable traits could be blended out. Mendel’s segregated “hereditary units”, or genes, explained how traits, even if unexpressed, could survive to benefit future generations.
Experts today consider Mendel the father of genetics.
“I feel that a lot of the questions we ask today are exactly the same questions that he asked back in the middle of the 19th century,” says UCLA's Leonid Kruglak, PhD, who considers Mendel his science hero.