Gregor Mendel and Charles Darwin.
As covered by a previous Augnet page, Gregor Mendel (1822-1884) conducted cross-breeding experiments on pea plants.
His work on genetic mutation was of value to the theory of Charles Darwin, although this was first noticed by other scientists only after both Mendel and Darwin had died.
Mendel discovered that various characteristics (height, colour, etc.) appeared in first and second generation plants in accordance with simple mathematical proportions.
But from the point of view of the theory of evolution first developed by Charles Darwin, the other discovery by Mendel - that of genetic mutation - is the most important.
This was that, although two parents pass on a variety of characteristics to their offspring, these characteristics cannot go beyond the limit of what was genetically contained within the original genes of the parents.
It is a principle of Mendelian genetics that no amount of breeding can produce species with completely new characteristics.
The inheritable characters (called "traits") are stable and constant.
Although traits can skip one or more generations and then reappear, when they do reappear they are exactly the same characteristics as they were previously.
Darwin believed that evolution came about through continual small differences between individuals, the best of which were preserved by natural selection.
The results of Gregor Mendel results confine this possibility within the limits of discrete groups.
This was acknowledged by geneticists, and led to their proposing another mechanism.
This relies on the fact that a miniscule number proportion of offspring are noticeably different from the parents. These are called mutants.
It is these mutants which evolutionists claim may occasionally, under changing environmental conditions, be better adapted than the parents and thus propagate successfully.
With further mutations, it is presumed that a new species will appear.
The observations of Mendel on genetic mutation provided evidence that such mutations go some of the way scientifically in explaining evolution.
This changed the basis of the theory of Charles Darwin so much that it is now called Neo-Darwinism.
It is fitting - or is it ironic?! - that Gregor Mendel, one of the followers of Augustine, made his mark in the field of science, which was an area of learning that the overwhelming intellectual influence of Saint Augustine of Hippo on the Middle Ages is said to have held back.
Self-knowledge and the Sciences in the Early Thinking of Augustine. A very scholarly article by Johannes Brachtendorf of Tübingen. Only for the brave!