[1] In his book, Dobzhansky applied the theoretical work of Sewall Wright (1889–1988) to the study of natural populations, allowing him to address evolutionary problems in a novel way during his time.

Dobzhansky implements theories of mutation, natural selection, and speciation throughout his book to explain the habits of populations and the resulting effects on their genetic behavior.

Dobzhansky illustrates that evolution regarding the origin and nature of species during this time in history was deemed mysterious, but had expanding potential for progress to be made in its field.

Darwin did not know that the monk Gregor Mendel was already working on experiments that would explain inheritance in terms of units of heredity that we now call genes.

The Dutch botanist Hugo de Vries developed a theory called mutationism in which most variations were inconsequential and could not lead to species change.

B. S. Haldane and Sewall Wright – showed that Mendel's laws could explain continuous variation in biological characteristics; and that natural selection could act cumulatively, giving rise to large changes.

[4] Many biologists fell into two camps: the geneticists, who mostly worked in the laboratory; and naturalists, who studied natural populations in the field and museums, and put much of their effort into taxonomy.

Meanwhile, naturalists were "like a man who undertakes to study the principles of the internal combustion engine by standing on a street corner and watching the motor cars whiz by.

Dobzhansky decided to attend the summer 1936 meeting of the Genetics Society of America in Woods Hole, Massachusetts.

He sent the invitation in April, and within a month he had suggested that the lectures be a springboard for writing a general treatise on evolutionary genetics.

"[7] After the lectures (for which he received $500), Dobzhansky returned to Pasadena, and in December Columbia University Press accepted his proposal for a book.

The pace of writing was helped by a riding accident in February 1937 in which he crushed his knee, rendering him immobile; and by April he was able to send a manuscript to Dunn for his perusal.

The first chapter is a short outline of the main points of the book: Evolutionary theory must account for variations on the level of the individual and also that of populations and species.

He considered examples of camouflage such as industrial melanism, in which moths and other arthropods evolve darker pigmentation when exposed to an environment with a lot of soot in it.

[10]: xxxi–xxxii In the seventh chapter, Dobzhansky discusses polyploidy, a condition (common in plants) where an organism has more than two complete sets of chromosomes.

[3]: 254  The only isolating mechanism that they had studied was sterility in hybrid organisms, so he devotes the ninth chapter to a particularly detailed analysis of the literature on this subject.

Dobzhansky used experimental breeding in laboratories and gardens, and also surveys related to species in nature to help support aspects of organic evolution.

Drosophila enabled researchers to gain a deeper understanding of how scientific knowledge about heredity has expanded and contributed to other areas of biology.

Mutations can result from external influences within the surrounding environment, especially if an organism inhabits an area with harsh living conditions.

Specific genes and alleles are then passed on to future generations to continue the trend of modern evolution that Dobzhansky presents in the book.

While analyzing chromosome structure in wild populations of Drosophila pseudoobscura, Dobzhansky discovered a surprising amount of undiscovered variability.

Dobzhansky suggested that the preservation of extensive variation would allow populations to evolve rapidly as environmental conditions change.

Dobzhansky laid out an advanced account of the evolutionary process in genetic terms, and he backed up his work with experimental evidence supporting the theoretical arguments.

This had a powerful impact on naturalists and experimental biologists, who quickly embraced this new understanding of the evolutionary process as one of genetic change in populations.

[21] In 1974 all the living founders of the modern synthesis (with the exception of Simpson and Bernhard Rensch) met with historians of biology in a conference to evaluate their work.

[5]: 569 Dobzhansky was plagued by a form of leukemia in his later years, but he remained vigorously active until the day before his death on December 18, 1975.

For Genetics and the Origin of Species Dobzhansky was awarded the Daniel Giraud Elliot Medal from the National Academy of Sciences in 1941.