Early contributions to evolutionary theory
Abbot Gregor Mendel
(1822-1884), Augustinian friar and founder of genetics
. His work and that of Darwin laid the groundwork for the study of life sciences in the twentieth century.
Catholics' contributions to the development of evolutionary theory included those of the Jesuit-educated French scientist Jean-Baptiste Lamarck (1744-1829) and of the Augustinian monk Gregor Mendel (1822-1884). Lamarck developed Lamarckism, the first coherent theory of evolution, proposing in Philosophie Zoologique (1809) and other works his theory of the transmutation of species. He constructed a genealogical tree to show the genetic connection of organisms.
Mendel entered the Brno Augustinian monastery in 1843, but also trained as a scientist at the Olmutz Philosophical Institute and at the University of Vienna. The Brno monastery was a centre of scholarship, with an extensive library and tradition of scientific research. At the monastery, Mendel discovered the basis of genetics following long study of the inherited characteristics of pea plants, although his paper Experiments on Plant Hybridization, published in 1866, remained largely overlooked until the start of the next century. He developed mathematical formulae to explain the occurrence, and confirmed the results in other plants. Where Darwin's theories suggested a mechanism for improvement of species over generations, Mendel's observations provided explanation for how a new species itself could emerge. Though Darwin and Mendel never collaborated, they were aware of each other's work (Darwin read a paper by Wilhelm Olbers Focke which extensively referenced Mendel). Bill Bryson writes that "without realizing it, Darwin and Mendel laid the groundwork for all of life sciences in the twentieth century. Darwin saw that all living things are connected, that ultimately they trace their ancestry to a single, common source; Mendel's work provided the mechanism to explain how that could happen". Biologist J. B. S. Haldane and others brought together the principles of Mendelian inheritance with Darwinian principles of evolution to form the field of genetics known as the modern evolutionary synthesis.
Changing awareness of the age of the Earth and fossil records helped in the development of evolutionary theory. The work of the Danish scientist Nicolas Steno (1638-1686), who converted to Catholicism and became a bishop, helped establish the science of geology, leading to modern scientific measurements of the age of the earth.