Genetics and God’s natural selection
Image by Tim Newcombe, background istockphoto
Mendel’s experiment in crossing red and white flowered pea plants.
(1) A red parent crossed with a white parent produces a red offspring. This occurs because, while characteristics are inherited from both parents, one (the red) is dominant in the first generation and the other (the white) is recessive.
(2) If a cross is now made between two of these red offspring, the next generation will have three reds to one white as shown.
It was a summer’s day in a monastery garden in Czechoslovakia over 100 years ago. Most of the monks saw nothing special about the pea plants growing there. To one of them, however, they were of great interest because he was performing scientific experiments with them.
What particularly fascinated Gregor Mendel was the way in which the plants handed on their characteristics to the next generation. ‘What could happen’, he thought, ‘if I crossed a white-flowered plant with a red-flowered? Would the next generation have red flowers or white? What if I crossed a tall plant with a short one? What height would the offspring be?’
As Mendel performed these experiments and carefully analyzed the results, he realized that he had discovered some fundamental laws concerning inheritance. Greatly excited, he published his findings in a scientific journal—but the scientific world ignored Mendel’s work completely. Discouraged, he abandoned his research. When he died in 1884, Mendel had no idea that 20 years later, he would have become world famous as the founder of a new science. Mendel’s work is now regarded as the beginning of the science of genetics, the study of inheritance.
In the preceding chapters we have looked at the rise of evolutionary theory and the evidence of the fossil record. Now we must consider whether—as is generally claimed—the findings of genetics support the idea of evolution.
Mendel published his findings in the late 1860s at just the time when Darwin’s theory was becoming immensely popular. Mendel published in a reputable journal and his paper was widely circulated and certainly known about. Yet it was not until 1900, 16 years after Mendel’s death, that the work was rediscovered and its importance realized.
Why were such vital discoveries ignored? The answer almost certainly is that they conflicted with Darwin’s theory of evolution. This is seldom admitted today, yet it is still true that what Mendel discovered disproved one of Darwin’s most important assumptions. This is demonstrated by the fact that after Mendel’s work was rediscovered, Darwinian evolution suffered a temporary eclipse. After a while, evolutionary thinking re-emerged in a slightly different form which was said to be quite consistent with Mendel’s genetics. As we shall see, however, the two are not consistent and both cannot be true.
What did Mendel discover that spoke against Darwin’s theory of evolution? This can best be answered by considering what he actually did. Mendel crossed various races of edible peas. When a red-flowered plant was crossed with a white-flowered, the offspring were found to be red-flowered. Mendel then crossed these red offspring with each other and found that they produced offspring of their own in the ratio of 3 reds:1 white.
We can best understand this by considering the genes involved in these crosses. A gene can be considered as a unit which determines a particular characteristic, in this case flower color. It can exist in one of two forms, one giving rise to red flowers and the other to white. The offspring of the original cross of red-flowered plants with white were all red-flowered, although they did in fact possess both a gene for red-flower and a gene for white.
Mendel concluded that the red gene must be dominant to white, so that any plant that possessed them both would be red. When these red plants were bred with each other, it was possible for two white genes to come together and so give offspring that were white. The chance that the offspring would receive at least one red gene is 3:1, as the diagram shows.
Mendel found that when he interbred the red-flowered plants obtained as the offspring of his original cross, he got white flowers as well as red. Darwin’s theory rested on the assumption that in such a case as this, the white characteristic was a new character acquired by the young plants which their parents had not possessed. After all, a race has got to acquire new characteristics if it is ever going to evolve.
Editor’s note added 27 August 2009: A great deal has happened in genetics since 1980 when this article was written. As well-known creationist scientist and writer Alex Williams pointed out when the article received its turn for airing on the net,
“Four different challenges to the text-book story of Mendel’s work circulated during the 1980’s and the matter was resolved only in a 1992 review article: Daniel L. Hartl and Vitezslav Orel, What Did Gregor Mendel Think He Discovered? Genetics 131: 245–253,1992. (available on-line in the journal’s archive).”
Alex also stated that there were good reasons for ignoring Mendel’s belief rather than just because it was anti-Darwinian, i.e.:
- Mendel’s 1866 article was entitled ‘Experiments in Hybridization’ so its subject matter was not about heredity.
- The conceptual framework for understanding heredity had not developed—in the 19th century, heredity was thought to simply be a part of reproduction that did not require separate characterization. Mendel’s work was rediscovered contemporaneously in 1900 by three different people (Hugo de Vries, Carl Correns & Erich Tschermak-Seysenegg) which illustrates that it was widely known, but its significance for heredity had not previously been understood.
- It was not ignored; most evolutionists simply looked upon hybridization as a means of recombining pre-existing features. What most biologists of the time were more interested in was the origin of novelty (e.g. William Bateson with his work on discontinuities, and Hugo de Vries with his work on mutations).
- Other’s tried to replicate Mendel’s work with other species and other characteristics but generally failed. We now know that most characteristics do not behave in the classic Mendelian manner so it was actually good science (it could not be replicated by others) that held back its acceptance.