Sewall Wright: biography of this American geneticist.

A summary of the life of geneticist Sewall Wright, and his contributions to science.

There are authors whose work has meant a leap for their field of knowledge. This is the case of Sewall Wright and his studies on genetics.

We will review the most important events in the life of this researcher as well as describe some of his most relevant contributions to the science of genetics, through a biography of Sewall Wright in summary format.

• Related article, "What is the genetic code and how does it work?"

Brief biography of Sewall Wright

Sewall Green Wright was born in the city of Melrose, state of Massachusetts, United States, in the year 1889.. He was the son of Elizabeth and Phillip. It so happened that his parents were first cousins, an interesting fact that would be of importance 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 home was very intellectual, which favored Sewall Wright's early interest in sciences such as mathematics and biology, which would later be fundamental in his education. He first studied at Galesburg High School, until 1906, when he graduated.

He then entered Lombard College itself, the university where his father taught. He studied mathematics, but he was also fortunate enough to receive classes from Wilhelmine Entemann Keywho was one of the first women doctors in the field of biology, a pioneer. This author was instrumental in the formation of Sewall Wright and his interest in the field of genetics.

In turn, Wright obtained her doctorate at Harvard University, no less. It was precisely at Harvard that he began his work as a researcher, working for the Bussey Institute. It was there that he had the opportunity to collaborate with William he had the opportunity to collaborate with William Ernest Castle, one of the first American geneticistswhose research focused on the study of mammalian coat shades and the factors that made them hereditary.

It was also at this time that Sewall Wright met Louise Lane Williams, whom he married in 1921. From this marriage three descendants were born, two sons, Richard and Robert, and one daughter, Elizabeth. The happy couple would share a lifetime together until Louise's death in 1975.

After his time at the Bussey Institute, Sewall Wright began working with the U.S. Department of Agriculture began working with the U.S. 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 assignment, as he would spend no less than three decades and finally retire in 1955.

Sewall Wright ended his days in the city of Madison, Wisconsin, where he finally passed away in 1988, at the age of 98.

Studies in population genetics

Now that we have taken a tour of Sewall Wright's biography, it is time to review his major contributions to the field of genetics, which were not few.

The first branch of genetics in which Sewall Wright excelled was population genetics.. Within this field he carried out research that had to do with inbreeding, partly, as we have already seen, moved by the case of his own parents, and how the fact of being first cousins could genetically affect their offspring.

In conjunction with that work, he also investigated both genetic drift and the 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 the father of the neo-Darwinian synthesis, also called the modern synthesis of evolution.

Sewall Wright also discovered some of the keys to understand population genetics and to be able to work with this concept in a mathematical way. One of them would be the inbreeding coefficient, which gives us information about the probability that the parents of an individual have a common ancestor based on the arrangement of the alleles of a particular gene.

The other tool created by Sewall Wright would be the F statistics or fixation indices, which tell us about the level of heterozygosity of a population, or in other words, the genetic disparity or similarity between the individuals of that particular population.

Continuing with the contributions to population genetics, thanks to Sewall Wright the mathematical basis explaining the genetic drift of species was established.. In fact, this concept can also be found written as the Sewall Wright effect. Genetic drift explains the factors that cause successive generations of a given species to undergo changes in the genetic sequence.

He also developed the concept of effective population size, i.e., the minimum size of a fictitious population that we would need in order to be able to make inferences that are adapted to the circumstances of the total number of individuals in the total population studied. To this end, a number of simplifications are used that statistically should not significantly alter the conclusions reached.

Evolutionary theory studies

Sewall Wright also studied in depth the relationship between genotype/phenotype and Biological fitness, which refers to the estimated offspring that a given individual will have during his or her lifetime. To this end, he he speaks of evolutionary landscapeshypothetical scenarios in which, depending on the height, the organism is more likely to reproduce.

According to genetic drift, the species will occupy the local peak and to reach a higher peak it will have to pass through a valley zone where its probabilities will decrease before ascending again, this time more strongly. This theory is valid for populations that are not too large. If they were larger, they could be divided into smaller groups, some of which would manage to move to the highest peak.

If there were also gene flow between the two groups, the changes achieved by one of them could be shared with the rest, eventually reaching the whole population. This mechanism is another of Sewall Wright's approaches and is known as the shifting equilibrium theory. is known as the shifting equilibrium theory. However, it is a controversial approach, since many evolutionists doubt that the conditions for this to happen are usually present.

In fact, this issue led him to a confrontation with his colleague Sir Ronald Aylmer Fisher, since he argued that populations would have to be smaller than most of them are for the theory proposed by Sewall Wright to fit, since the effects of genetic drift would be diluted by such large populations.

Path analysis or path analysis is another of Sewall Wright's contributions. It consists of a statistical system, created in 1921 by this author, which since then has been used in a variety of scientific disciplines because of its great usefulness. Through a graphical model, path analysis shows the researcher the causal relationships between different variables..

Guinea pig study

Sewall Wright sought to investigate possible methods to improve in some way the characteristics of some species of animals and plants. To this end, he conducted an ambitious experiment with a population of 80,000 guinea pigs. He established a group in which mating would take place between siblings, while in the other half of the population the crosses would be random.

The results were the basis that allowed him to define the theory of shifting 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 were made smaller and thus restricted the possibility of gene flow.

These studies were a great success among his studentsThese studies were a great success among his students, who also proposed new research to further advance the field of genetics. One of those who most appreciated Sewall Wright's contributions was Jay Lush, who would later become a reference in quantitative genetics studies.

For all this work and much more, Sewall Wright is today considered one of the most important geneticists in the field of quantitative genetics. is today considered one of the most important geneticists in the history of genetics.He received a whole series of awards that accredit his importance in this field of knowledge.

Bibliographical references:

• Provine, W.B. (1989). Sewall Wright and evolutionary biology. The University of Chicago Press.
• Wade, M.J. (1992). Sewall Wright: gene interaction and the shifting balance theory. Oxford surveys in evolutionary biology.
• Wright, S. (1931). Evolution in Mendelian populations. Genetics.
• Wright, S. (1932). The roles of mutation, inbreeding, crossbreeding, and selection in evolution. Proceedings of the Sixth International Congress on Genetics.
• Wright, S. (1949). The genetical structure of populations. Annals of eugenics. Wiley Online Library.