A new analysis of high school biology textbooks shows that emphasis on the topic of evolution decreased sharply in the decade ahead of the Scopes trial (1925). However, contrary to the conventional scholarly view [1], relative priority of the topic retuned to pre-Scopes levels by 1935 and did not decrease significantly in the decades that followed.

The graph below is based on direct review and analysis (see table) of 80 American high school biology textbooks published between 1907 and 1969.


This graph was generated in Excel by plotting the data gathered through direct examination of 80 high school textbooks published between 1907 and 1969. It shows a clear decline in the priority of the topic of evolution in the years ahead of Scopes trial in 1925, restoration of the topic to earlier levels by 1935, a secondary decline from about 1945 to 1955 and then a rise into the 1960s.

The data strongly suggest that Scopes, or more accurately the general anti-evolution movement of the early 1920s, had an impact on the treatment of the topic of evolution in biology textbooks. However, the impact was temporary. By the later 1930s, the topic had returned to its pre-Scopes status, and remained at least at that status level through the 1960s.

The dip at toward the middle of the 1950s is almost entirely attributable to the popularity of one textbook, Moon’s Modern Biology (see article). It is interesting to compare this chart with a similar chart based on the same data set of the relative treatment of the topic of eugenics.


It became common practice starting in 1924 for publishers to shave off the burrs that so irritated fundamentalists – the word ‘evolution,’ the inclusion of “man” in the Haeckel embryo “recapitulation” series, the portrait of Darwin or mention of his book, Descent of Man. But authors adjusted without much struggle or loss, and quickly found perfectly serviceable solutions for presenting the topic appropriately within their selected narrative frame.

In ranking the relative priority of the topic of evolution, I did not penalize a text for not indexing the word ‘evolution’ or indexing the topic under a synonym. Nor did I necessarily penalize a text for placing the topic of evolution at the back of the book. It has been suggested that the placement of the topic of evolution in a text’s closing chapters was a concession to conservative forces. But this placement was common in both college and high school textbooks, particularly in phylogenetic and economic texts, long before Scopes.

Perhaps more importantly, I made NO ADJUSTMENT for textbook popularity. Instead, I have chosen to let copyright date dictate inclusion, and therefore relative weight, presuming that publisher investment in copyright-worthy editions correlates to popularity in general. This tracks fairly well with what is known. Several sources state that from the late 1950s through the mid-1960s, Modern Biology commanded 50% of the market, Exploring Biology held 25%, with the remainder divided among a dozen or so competitors. Between 1946 and 1969, Modern Biology had 8 published editions, while Exploring Biology had 4.

With the above decisions in place I took into account several factors to arrive at a final ranking: 1) The state of evolutionary theory at the time of a textbook’s publication; 2) The textbook’s style or category (phylogenetic, economic, unity of life or normative); and 3) The integration of the topic into the text – was the topic where it should be or was it tacked on, buried in the biography section for example?

[NOTE] After publishing this post I went back and carefully reread the article referenced in its title, Gerald Skoog’s “Topic of Evolution in Secondary School Biology Textbooks: 1900-1977” (1979). Upon review, I found to my surprise that Skoog’s data closely aligns with my findings. For example, Skoog writes, “… there was a continued increase in the emphasis on evolution in the textbooks from 1900 to 1950. This trend was reversed in the 1950s when the concept was deemphasized slightly” (622). It seems I took away the same “emotional truth” other scholars have after reading Skoog’s scathing conclusion, which includes, “the professional biologist’s acceptance of evolution as an important and unifying idea of the discipline had not been powerful enough to counterbalance the rejection and suppression from opinion, legislation, and pressures exerted by organized religious groups, administrative edicts, publisher’s caution, threatened teachers, and numerous other forces” (635).

[1] For examples see Nelkin, 1977, p. 16; Gould 1983, p. 282; Toumey, 1991, p. 691; Numbers, 1992, pp. 238-239; Larson, 1997, p. 231; Scott, 1997, p. 272; Rudolph, 2002, p. 148; Larson, 2003, pp. 87-88. See also the BSCS’ self-published history, The BSCS Story, which claims the group repaired the “post-Scopes purge of evolution in biology books.” Engleman 2001, 28.


Engleman, Laura, (ed.). 2001. The BSCS Story: A History of the Biological Sciences Curriculum Study.Colorado Springs: BSCS.

Gould, Stephen Jay. 1983. Hen’s Teeth and Horse’s Toes. New York: W. W. Norton & Company.

Grabiner, Judith V., Peter D. Miller, 1974. “Effects of the Scopes Trial.” Science 185: 832-837.

Ladouceur, Ronald. 2008. “Ella Thea Smith and the Lost History of American High School Biology Textbooks.” Journal of the History of Biology 41: 435-471.

Larson, Edward J. 1997. Summer for the Gods: The Scopes Trial and America’s Continuing Debate over Science and Religion. Cambridge, Massachusetts: Harvard University Press.

–. 2003. Trial and Error: The American Controversy over Creation and Evolution, 3rd ed. New York: Oxford University Press.

Nelkin, Dorothy. 1977. Science Textbook Controversies and the Politics of Equal Time. Cambridge, Massachusetts: The MIT Press.

Numbers, Ronald. 1992. The Creationists: The Evolution of Scientific Creationism. Berkeley: University of California Press.

Rudolph, John L. 2002. Scientists in the Classroom: The Cold War Reconstruction of American Science Education. New York: Palgrave.

Scott, Eugenie C. 1997. “Antievolutionism and Creationism in the United States.” Annual Review of Anthropology 26: 263-289.

Skoog, Gerald. 1979. “Topic of Evolution in Secondary School Biology Textbooks: 1900-1977.” Science Education 63: 621-640.

Toumey, Christopher P. 1991. “Modern Creationism and Scientific Authority.” Social Studies of Science 21: 681-699.