Growing up, I understood that when two people (especially family members) behaved…, or responded the same to eventualities, they’d be branded as two peas in a pod. But science and experience tell us that old saw is misguided. Beyond having been produced in the same fruit (the pod), and appearing similar, peas in a pod are genetically different. They may not be the same at all, just as kittens in a litter, or any two children in a family (excepting identical twins) are not the same.
But how different are they? And what could someone figure out about those differences? Given patience, diligence, and focus, in the case of peas, the answer is “a lot.” Just take a few minutes with me to consider the life of Gregor Mendel, remembered as a monk who loved plants.
Born in Hynčice on 20 July, 1822, Mendel grew up at the very time modern science, in this case botany, was liberated from the classical world view. In 1804, Nicholas de Saussure had explained that plants take in carbon dioxide, making it part of biomass. Alexander von Humboldt had brought attention to patterns of global climate and plant distribution. By the time Mendel was a year old, Amici had described tubes growing from pollen of a Portulaca. In 1828 Adolphe Brongniart authored the first book on fossil plants and Robert Brown would soon publish the first description of a cell nucleus.
Mendel’s formal study of botany and agriculture would have been based on works of Humphrey Davie, John Antony Chaptal, and (most importantly) Justus von Liebig, publications that established the importance of chemistry in understanding agricultural science. He reached adulthood in a post-medieval, post-renaissance, post-enlightenment era. Even as a Friar in an Augustinian abbey, Mendel was free to ask questions that just a century earlier were considered none of man’s business.
He wondered why pea plants showed such individual characteristics, just as you might wonder why one child in a brood would have blue eyes, or auburn hair, while the others do not. The peas Mendel grew (all of which were harvested and shelled, scored for characteristics, and then eaten by the Friars) could have differing seed shape, flower color, seed color, pod shape, pod color, inflorescence structure, and plant height. He must have had a math streak, because Mendel wondered, most earnestly, how frequently the characteristics appeared in each new crop of seed. What were the chances that different characters would show up in a new generation? How were those chances affected by the parents? Were there rules to the game, could the chances be estimated statistically? Can you game the system?
Answering some of those questions, Mendel hybridized, flowered, studied, and served (that is, the Friars ate the peas) seed from tens of thousands of pea plants at Brno Abbey over a period of seven to eight years. As with so many scientists, his concentrated period of research ended when (in 1867) he was appointed Abbot of the monastery.
Worth noting, Mendel was trained in physics, and was born the same year as Francis Galton. This means Mendel was likely keenly aware of the advances in statistical technique and analysis made by Galton. It was Galton who introduced the phrase “nature versus nurture” in 1874, having published (1869) his own concepts of the significance of inheritance in the book Hereditary Genius. And it is Galton, an early commentator on selection, who introduced the term eugenics.
But Mendel was focused on peas, and variation, and chances. Though his brother Friars burned Mendel’s notes and materials at his death, thankfully Mendel did not commit the ultimate scientific sin, which is failing to publish your work – summarized in the quaint directive: “Don’t get it right, get it writ.” In 1866, before moving into administration, Mendel published his data and conclusions in the regional scientific journal, Verhandlungen des naturforschenden Vereines in Brünn.
Scientists mourn the fact that Mendel’s observations languished in a non-mainstream journal for over 30 years, at the very time controversy stormed over the mechanisms that could possibly explain evolution. But in reviewing much of the literature from that time, I see it a bit differently. In 1865, people were not ready to appreciate the impact of Mendel’s conclusions. He made oral presentations, but there must have been something about his island of thought that could not be bridged to other mounds. That would change, and the world of biology would be cast into a new paradigm, in 1900.
If you are interested in the longer story, check out my Footsteps article on Cell Biology.