Western History 168: What important breakthroughs impacted the Life Sciences during the 19th century?

The biological sciences made great strides in the 19^th century  with the term itself being coined by Karl Friedrich Budach in 1800. Jean-Baptiste Lamarck  (1809) proposed a theory of evolution that posited the importance of the inheritance of acquired characteristics. However his work here was superseded by Charles Darwin and Alfred Wallace’s Theory of ‘descent through modification’ (1858).

Although Darwin did not use the word evolution in his earlier work the notion of natural selection as a key driver for evolutionary change fundamentally changed the nature of how we understand the life sciences. It provided the overriding platform on which our understanding of both biology rests.

Charles Darwin source: biography.com

Like Copernicus's earlier Heliocentric model of the universe Darwin's work challenged the privilege notion of humanity in the universe. The ladder of life was not crowned by our species.

Austrian monk Gregor Mendel (1865) would add to Darwin’s work by elucidating and describing  the rules that seem to underpin genetic inheritance.The Principle of Segregation states that there are two genes per trait and that these segregate when an animal makes an egg or a sperm. The Law of Independent Assortment argues that genes in a pair are distributed independently. Much of Mendel's work on pea plants was 'lost' but it was re-discovered years later (by Hugo De Vries in 1900) and now plays an important role modern science of genetics.

Gregor Mendel - Schematic showing how genes combine during Fertilization source: biomedcentral.com

In terms of cell biology Theodor Schwann and Matthias Schleiden (1839) made the case that all living organisms are made up of cells (Cell Theory). Rudolf Virchow (1858) advanced this idea further by showing that all cells come from pre-existing cell. This built further on the discovery of the mammalian egg by Karl von Baer (1826) and Martin Barry's (1843) revelation that showed how egg and sperm fuse in the case of rabbit egg fertilization.

Organic Chemistry and with it biochemistry came of age in the 19^th century with Friedrich Woehler’s synthesis of urea (1828) The enzyme pepsin, that acts to facilitate protein digestion was identified by Schwann in 1836. Before that chlorophyll, which plays a vital role in Photosynthesis, was identified in 1817 with Friedrich Miescher (1869) and Emil Fischer (1884) adding to our knowledge of nucleic acids and sugars by their respective biochemical discoveries .

Adding to this work was the tremendous accomplishments of the Frenchman Louis Pasteur, the Father of Immunology, who showed how microorganisms are responsible for Fermentation (Pasteur's name is associated with the high temperature process used to kill bacteria in milk). Pasteur also produced the first vaccine for rabies and in 1864 dealt the final blow to the age old theory of Spontaneous Generation.

Pasteur's Test of Spontaneous Generation source: AmoebaMike

Ignác Semmelweis and Joseph Lister would make use of Pasteur's Germ Theory in their development of antiseptics thereby revolutionizing our understanding of disease management and pathology.

Lord Joseph Lister source: rcseng.ac.uk

While Antiseptics stands as the one arm of modern medicine the other is anaesthetics that was given a vital lift by Scotsman James Simpson (1847) and his pioneering work with chloroform. This would open the door for pain reduced surgeries.

As mentioned the Chemistry and Biology into the fledgling Biochemistry was an emerging reality of the 19^th century and breakthroughs were all the more common as scientists learnt more about the action of germs in causing disease. Martinus Beijernick for one identified a new pathogen that caused the Tobacco Mosaic plant disease. It was much smaller than a  bacterium and he named it the virus.