Some authors whose work has been a leap forward for their area of knowledge. This is the case with Sewall Wright and his studies in genetics.
We will review the most important events in the life of this researcher and describe some of his most relevant contributions to the science of genetics, using a biography of Sewall Wright in summary format.
Brief biography of Sewall Wright
Sewall Wright was born in the town of Melrose, Massachusetts, United States, in 1889. He was the son of Elizabeth and Phillip. There was the circumstance that his parents were sibling cousins, an interesting fact that would be important to Sewall Wright’s curiosity about inbreeding and its implications, as would later be reflected in some of his research.
When Sewall was very young, the family moved to Galesburg, Illinois, as his father had secured a teaching position at Lombard College. The atmosphere in the Wright house was very intellectual, which fostered Sewall Wright’s early interest in sciences such as mathematics or biology, which would later be fundamental in his training. He first studied at Galesburg High School until 1906 when he graduated.
He then entered Lombard College, the university where his father taught. He pursued a career in mathematics, but was also fortunate enough to receive lessons from Wilhelmine Entemann Key, Who was one of the first female physicians in the field of biology, a pioneer. This author played a key role in Sewall Wright’s training and interest in the field of genetics.
In turn, Wright obtained his doctorate, neither more nor less than at Harvard University. It was in this institution that he began his duties as a researcher, working for the Bussey Institute. It was in this center where he had the opportunity to collaborate with William Ernest Castle, one of the first American geneticistsResearch has focused on studying the nuances of mammalian fur and the factors that made them hereditary.
It was at this time that Sewall Wright also met Louise Lane Williams, whom he married in 1921. From this marriage were born three descendants, two men, Richard and Robert, and a woman, Elizabeth. The happy couple shared their lives until Louise’s death in 1975.
After his time at the Bussey Institute, Sewall Wright started collaborating with the US Department of Agriculture. In 1925 he moved to the University of Chicago to work as a researcher in the Department of Zoology. This would be his last destination, as he would spend no less than three decades and finally retire, as early as 1955.
Sewall Wright ended his days in the town of Madison, Wisconsin, where he finally died in 1988, at the age of 98.
Population genetics studies
Once we have visited Sewall Wright’s biography, it’s time to review his main contributions to the field of genetics, which were not uncommon.
The first branch of genetics that Sewall Wright excelled in was population genetics.. In this area he conducted research which had to do with inbreeding, in part, as we have seen, moved by the case of his own parents, and how being cousins could genetically affect his offspring.
Along with this work, he also studied both genetic drift and mating systems of different species. Thanks to Sewall Wright and other authors such as John Burdon Sanderson Haldane or Sir Ronald Aylmer Fisher, population genetics experienced a major breakthrough. In fact, Wright is considered to be the father of the Neo-Darwinian Synthesis, also known as the Modern Synthesis of Evolution.
Sewall Wright also discovered some of the keys to understanding population genetics and being able to work with this concept mathematically. One of them would be the inbreeding coefficient, which tells us about the probability that the parents of an individual have a common ancestor depending on the arrangement of alleles of a particular gene.
The other tool created by Sewall Wright would be that of F statistics or fixation indices, which tell us about the level of heterozygosity of a population, or what is the same, the genetic disparity or similarity between individuals of “ this particular population ”.
Pursue contributions to population genetics, thanks to Sewall Wright the mathematical basis for the genetic drift of the species has been established. In fact, this concept can also be found under the name of the Sewall Wright effect. Genetic drift explains the factors that cause successive generations of a given species to undergo changes in genetic sequence.
He also developed the concept of effective population size, that is, the minimum size of a fictitious population that we would need in order to be able to make inferences that fit the circumstances of the total number of individuals in the total population studied. This is done using a series of simplifications which, statistically, should not significantly change the conclusions drawn.
Studies of the theory of evolution
Sewall Wright has also extensively studied the relationship between genotype / phenotype and biological fitness, which refers to the estimated offspring that a particular individual will have in their lifetime. for that he talks to us about evolving landscapes, Hypothetical scenarios in which, depending on height, the body is more likely to reproduce.
Depending on the genetic drift, the species will occupy the local peak and to reach a higher, it will have to cross a valley area in which its probabilities will decrease before rising again, this time with more force. This theory is valid for populations that are not too large. If they were tall, they might split into smaller groups, some of which would be able to move to the higher peak.
If there was also gene flow between the two groups, the changes made by one of them could be shared with the others, eventually reaching the total population. This mechanism is another of the approaches of Sewall Wright and it is known as the theory of shifting equilibrium. However, this is a controversial approach, as many evolutionists wonder if the conditions are generally in place for this to happen.
In fact, this question led to a confrontation with his colleague Sir Ronald Aylmer Fisher, as he argued that populations should be smaller than they are for the majority in order for the theory proposed by Sewall Wright to be suitable, since the effects of genetic drift would be being diluted by being in such large populations.
Another of Sewall Wright’s contributions is route analysis or route analysis. It is a statistical system, created in 1921 by this author and which has since been used in various scientific disciplines for its great utility. Through a graphic model, the path analysis shows the researcher the causal relationships between different variables.
Study with guinea pigs
Sewall Wright attempted to study possible methods of improving in some way the characteristics of certain animal and plant species. This is why he carried out an ambitious experiment with a population of 80,000 guinea pigs. He established a group in which matings would be done between siblings, while in the other half of the population, crosses would be random.
The results were the basis that allowed him to define the theory of change in equilibrium, which we have already mentioned above. According to this concept, Sewall Wright claimed that the adaptive evolution of a given group of individuals could occur more easily if these groups became smaller and thus limited the possibility of gene flow.
These studies were very successful among his studentsThis has also raised new research to continue advancing in the field of genetics. One of Sewall Wright’s most appreciated contributions was Jay Lush, who would in fact become a benchmark in studies. of quantitative genetics.
For all this work and more, Sewall Wright today he is considered one of the most important geneticists in historyai has received a series of awards which attest to its importance in this area of knowledge.
- Provine, WB (1989). Sewall Wright and evolutionary biology. The University of Chicago Press.
- Wade, MJ (1992). Sewall Wright: The Interaction of Genes and the Theory of Equilibrium Change. Oxford Investigations in Evolutionary Biology.
- Wright, S. (1931). Evolution of Mendelian populations. Genetic.
- Wright, S. (1932). The roles of mutation, inbreeding, interbreeding and selection in evolution Proceedings of the Sixth International Genetics Congress.
- Wright, S. (1949). The genetic structure of populations. Annals of Eugenics. Wiley Online Library.