The man behind the peas

In 1859, Charles Darwin wrote in On the Origin of Species that "the laws governing inheritance are quite unknown." Unknown to him maybe, but three years earlier, an obscure Augustinian friar was toiling away in his garden to discover those laws -- laws that would eventually bear his name.

By now, the legend of Mendel's pea-crossing experiments is infamous in the annals of science, but the man behind the peas remains little appreciated, if not misunderstood. Enter the Gregor Mendel: Planting the Seeds of Genetics exhibition, developed by The Field Museum in Chicago, and now on its fifth and final US stop at the Academy of Natural Sciences in Philadelphia before the artifacts return home to the Mendel Museum in Brno, Czech Republic. Mendel may have dressed as a friar, but he had the heart and mind of a scientist. With a touch of affectation, the exhibition presents a comprehensive overview of the inquisitive man who revolutionized modern biology.

Johann Mendel was born in 1822, the son of tenant farmers, and adopted the name Gregor in 1843 when he joined the Augustinian order, but not many artifacts remain from his early life. One of the exhibition's earliest documents shows Mendel's "certificate of proficiency in fruit and grape growing" from 1846: the roots of his passion for plant reproduction. He seemed less cut out for life in the parish. A letter dated October 4, 1849, from Mendel's Abbott to the local Bishop, states that Mendel was relieved of his parish duties and assigned to teach at the local middle school in Brno, where he worked for 14 years, and reportedly kept a stash of dried peas in his pocket to throw at dozing students. During that time, Mendel was also in charge of the Abbey of St. Thomas herbaria's extensive collection of dried and pressed plants, many of which are on display in the exhibit.

The exhibition's most endearing items are numerous bits of Mendel's personal scientific belongings and correspondences. Although Mendel did not have any scientific degree, he was educated at the University of Vienna, where he studied under Christian Doppler -- of the "Doppler effect" fame -- and was a diligent hands-on experimenter in a range of scientific fields, including astronomy, meteorology, and botany. From his scientific "toolbox," visitors can see his personal telescope and sunspot drawings, his brass barometer-thermometer and meteorological recordings, the 179X magnification microscope he used to precisely cross-pollinate his peas, and the garden tools he used to plant his Pisum sativum specimens.

Little remains from Mendel's infamous eight-year experiment of cultivating, crossing, and counting tens of thousands of peas. The exhibition has informative and interactive displays explaining the genetics of mendelian inheritance for young and old, but for those well-versed in Punnett squares, sadly only two fragments of Mendel's original notebooks survive from this period. There are, however, original manuscripts of his 1866 publication "Experiments in Plant Hybrdization" in Proceedings of the Natural History Society of Brünn, as well as the few publications that cited the paper over the next few decades, and the eventual "rediscovery" of his work in 1900.

Mendel's copy of Wonders of the Invisible World by Gustav Jäger, 1867

Mendel was widely versed in the science of the day, and a number of his personal books are on display, often with Mendel's comments and notations in the margin. Perhaps the most striking is Mendel's German copy of Darwin's On the Origin of Species, which the exhibition curators have left open to page 21 marked up with two dashes and an exclamation point highlighting the line: "There are so many laws regulating variation, some few of which can be dimly seen." Mendel likely read Darwin's Origin half-way through his pea experiments, so one can only speculate why he was marking the page. I like to think he was saying, "I can see the laws!"

The exhibition is padded out with a whirlwind 20th century history of genetics, from the dawn of cytology and the discovery of DNA to sequencing the human genome, and it includes many original pieces of artwork inspired by Mendel and genetics. But the show's greatest strengths are the personal touches. Toward the end of the Mendel section, we see the apiary in which he tried to replicate his pea experiments using bees toward the end of his life. As he didn't know about haplodiploidy, those experiments were doomed to failure.

After over an hour in the exhibition, I was running out of steam, but hidden away in a back corner in an unassuming little glass case, I stumbled on a pair of eyeglasses. Mendel's portrait might not be as well known as Darwin's, but to anyone who is familiar with his face, Mendel's little round spectacles are the equivalents of Darwin's beard -- a powerful symbol of modern biology and the great scientists who have uncovered its secrets. As I stared at them, I paused to marvel; these thin bits of glass are the quite literal lenses through which Mendel saw the nature of life.

Not long before Mendel died in 1884, he said to a colleague, "my time will come." Indeed it has.

Elie Dolgin
mail@the-scientist.com

Gregor Mendel: Planting the Seeds of Genetics runs from May 24 through September 28 at the Academy of Natural Sciences in Philadelphia: 1900 Benjamin Franklin Parkway, 215-299-1000.

All photos (except Mendel's eyeglasses): © Stepan Bartos