Mendel and Evolution

Mendel, Darwin and Evolution

Darwin's Theory of Evolution has faced many challenges since the theory was first presented in 1859. The recent challenges by intelligent design advocates are not even the most serious of these challenges. The most serious challenge to Darwinism was by scientists in the late nineteenth century and early twentieth century. It resulted in a period called the "Eclipse of Darwinism" that lasted until about 1940. During this period, Darwinism fell out of favour amongst scientists. The problems of heredity, the impasse that Darwin had recognized when he published the Origin of Species, had finally caught up with the theory. Darwinism was rescued by modifying the original theory to include the work of Gregor Mendel. Darwin's Theory of Evolution, so often a symbol of the clash of religion and science, had been rescued by the work of a Roman Catholic monk, Gregor Mendel. The sponsoring organization for Mendel's research was an order of Monks, the Order of St. Augustine in Brno (Czech Republic).

By the turn of the twentieth century, Darwin's Theory of Evolution was already falling out of favour as an explanation for evolution. With good reason. Although Darwin's theory of evolution by natural selection was initially welcomed, there were two very big holes in the theory. One was the explosion of life forms in the early Cambrian period with no apparent transitional forms of life leading up to these species. The other was heredity. Darwin proposed that with the natural variations that occur in populations, any trait that is beneficial would make that individual more likely to survive and pass on the trait to the next generation. If enough of these selections occured on different beneficial traits you could end up with completely new species. But Darwin did not have an explanation for how the traits could be preserved over the succeeding generations. At the time, the prevailing theory of inheritance was that the traits of the parents were blended in the offspring. But this would mean that any beneficial trait would be diluted out of the population within a few generations. This is because most of the blending over the next generations would be with individuals that did not have the trait. Mendel had the answer to Darwin's impasse. Traits were not blended, but inherited whole. And because of Mendel's proposition of recessive and dominant traits, a trait that might disappear in one generation might reappear in the following generation. Mendel's work was incorporated into Darwin's original theory to give us our modern Neo-Darwinism.

Modern biographies of Mendel are generous in their praise of Gregor Mendel's patience and perception in choosing the pea plant as the subject of his studies and then following through for several years and thousands of crosses to eventually come up with his laws. Mendel chose pea plants partly because they had easily identifiable features such as wrinked or round peas or yellow or green pea pods, that they can self-fertilize and it is easy to protect them from cross-fertilization. But he had a problem. If you self-fertilized some pea plants with green pods they would always produce pea plants with green pods even through more than one generation. But if you self-fertilized other pea plants with green pods they would produce mostly plants with green pods but some with yellow pods. Although the plants looked similar (same phenotype) they were obviously different genetically (different genotypes). Similar problems occurred with every trait that he was testing. Mendel knew he had to start with true-breeding plants which means that he had to produce a set of plants that when self-crossed would always produce the same phenotype. This meant two years of tedious work before he could even start his hybridization studies [_1_] . Considering this, the generous praise for Mendel's patience might not be generous enough.

After developing his set of true-breeding plants, Mendel spent years making thousands of crosses through multiple generations of plants. This was more tedious than most would think. Pea plants have both male and female organs. While this has some advantages, it also meant that if you wanted to cross plants you would have to make certain they didn't self-fertilize first. Mendel would have to perform surgery on each target plant by cutting off the male organs (stamens) while the plant was still immature. When the time came to make the cross, Mendel would use a paintbrush to brush some pollen off the anthers of the donor plant and paint the pollen onto the stigma (part of female reproductive structure) of the target plant. He would then wrap a bag around the flower to prevent other pollen from landing on the stigma.

Mendel saw both randomness and reason in his results. In some ways, Mendel's genetics was similar to a casino dice game. Any roll of two dice could result in any of 11 different results, 2 through 12. But if you roll long enough you will see patterns. For instance, you might notice that 7 will come up 6 times as often as a 2. One of Mendel's innovations was to look at inheritance of traits as a random event and analyze the results based on probabilities. This may have been one reason why his paper was ignored. Random events, statistics and probabilities were part of the language used by nineteenth century physicists, but not nineteenth century biologists.

We can follow some of Mendels's logic by following one of his experiments. Mendel took true-breeding pea plants that produced only yellow peas and crossed them with true-breeding pea plants that produced only green peas. All offspring from these crosses had yellow seeds. The green trait had completely disappeared in the first generation. But then Mendel took this first generation (F.1) , and self-crossed them. He found that 6022 of the offspring of the second generation (F.2) had yellow seeds and 2001 had green seeds. From this we could guess that the genetic material that contributed to green peas must have been preserved in that first generation but that it was being masked by something more powerful..the genetic material that coded for yellow peas. Yellow peas were dominant and green peas were recessive. The ratio of the results in the second generation is very close to 3:1. This is significant as well. This ratio can be explained if the inheritance of traits depended on paired elements that are recombined (not blended as Darwin believed) in the offspring. In this experiment a Yellow-Green pair would show as a yellow pea. But if we crossed many Yellow-Green plants we could get only 4 different permutations; Yellow-Yellow, Yellow-Green, Green-Yellow, and Green-Green. Three of them result in yellow peas, and only one, the Green-Green, results in green peas. The diagram below (taken from a early book by Thomas Hunt Morgan) illustrates inheritance through two generations (F.1. and F.2.) of the yellow/green trait.

Inheritance with Mendel Peas

The fruit of Gregor Mendel's patient research was finally published in the the Proceedings of the Natural History Society of Brünn in 1866. No-one seemed to care. This important work was cited in scientific literature about a dozen times in the next 35 years. Around the turn of twentieth century, Mendel's work was rediscovered by several biologists (Correns, deVries) and would develop into a completely new discipline within the field of biology (genetics). It would also help end the "eclipse of Darwinism". Neo-Darwinism would keep many of the original ideas presented by Darwin but use Mendel's genetic laws to help explain how beneficial traits could be passed on from generation to generation.

These discoveries would prove important to the rehabilitation of Darwin's theories. They would also prove important well beyond evolutionary theories, affecting many areas of biology and medicine. It affected the lives of billions of people by helping to develop new hybrid food strains that were either more productive, more nutritious, more disease resistant or had better taste. The Green Revolution and foods that we take for granted such as canola oil were possible in large part due to Mendel's work.

Even though Gregor Mendel was a monk, his work is rarely considered in debates on the relationship of the church and science. It is typically considered a curiosity. Even when the church's role is explored, it is dismissed as being a passive source of funding for research. Richard Dawkins, a prominent critic of the church's and religion's role in society, presents this view in The God Delusion:

... Mendel, of course, was a religious man, an Augustinian monk; but that was in the nineteenth century. when becoming a monk was the easiest way for the young Mendel to pursue his science. For him, it was the equivalent of a research grant.

Richard Dawkins is joined by many others who feel it possible to reach back over 150 years and assess the inner motives and religiosity of a long-deceased monk. Their diagnoses are based on a very selective look at Gregor's biography. The monks who worked and prayed daily with Gregor Mendel may have disagreed with their diagnosis. Two years after the publication of Mendel's work, the monks of Brno held an election for a new abbot. The unanimous choice was Gregor Mendel.

Even if Mendel wasn't passive in his church, the church may have been passive in Mendel's research. This is argued by many who believe in the conflict thesis. This argument ignores the obvious. Augustinian monasteries have never been known for their democratic management techniques. How Mendel spent his day was determined by the 'rule' of the religious order and the abbot of the monastery. If Mendel was spending a lot of time studying heredity it is because it was one of his responsibilities. The responsibility which consumed much of Mendel's time for two decades may have been decided for him in the decade before his arrival at the monastery. In 1837, there was a meeting of the Sheepbreeders association of Brno. In attendance was Cyril Napp, president of a local organization supporting hybridization research and abbot of the Augustinian monastery of Brno. As one might expect, there was much talk about breeding. But Napp suggested an alternative topic: "the question for discussion should not be the theory and process of breeding, but what is inherited and how [_2_] .

Napp was not the only monk that would influence Mendel. Mendel took charge of the monastery's research garden in 1846. His predecessor at the garden, Matthew Klacel, was also studying heredity and evolution. Klacel had a special interest in the study of peas, perhaps influencing Mendel to continue the study. As Mendel was developing his theories he would have been able to bounce his ideas off his friend, Klacel, and other friars known to be interested in botany [_3_] .

Having the moral support of your supervisor and colleagues is not enough to produce superior research. There was also a physical record of the monastery's commitment to research. There were two different one hectare plots devoted to heredity research and a greenhouse that enabled Mendel to develop controls for his studies. More importantly, the monastery allowed Gregor the time necessary to finish his research and two full-time assistants to help him complete it [_4_] . You can still find articles that assume that Gregor conducted his research in his spare time. Given the time-consuming nature of the work it is doubtful that Mendel could have completed the work by himself even if he worked full-time on his research.

Would anyone else have supported Mendel's work at that time? Certainly not the established scientific community. His work was rarely even mentioned for about 35 years. The academic community would not have had the patience to wait for the fruit of Mendel's work. Mendel took over the monastery's experimental garden in 1846. His paper was published in 1866.

Dawkins does provide us with an interesting question. If the church's contribution to the final discovery of Mendel's Laws of genetics is not considered significant to the debate on church and science, what contributions would be considered significant? We must remember that the monastery tasked several different researchers (including Mendel) over a 30-year period to study heredity, allocated large plots of land within the monastery for this research, and used monastery funds to build a greenhouse which was used to develop controls for Mendel's research. Two full-time assistants were also assigned to help Mendel with his research. These weren't Mendel's decisions because Mendel was not the abbot. If the church's involvement here is not significant other than as a 'source of research grants', then perhaps Dawkins and other conflict theorists have set the bar so high that it guarantees that no involvement of the church in any scientific advance will ever be considered significant. Dawkins has engineered the discussion so that he will always win, not for a better understanding of the underlying issues.

Evolution is a favourite example for those that believe in an inherent conflict between science and religion. And it is Darwin that is typically the focus of these discussions. But current evolutionary theory doesn't just derive from Darwin, but also from Gregor Mendel, a Roman Catholic monk. It is tempting for conflict theorists to disassociate Mendel from his role as a monk and treat his work as an individual achievement. But monks live in a community. In a community you must carry the weight assigned to you. The work that led to the discovery of laws of genetics was his weight.

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Mendel, Darwin and Evolution