 In "Trying Biology" Robert Shapiro examines many of the eminent biology textbooks in the 1910–1920s, and finds that while they may have avoided the word "evolution" to placate anti-evolutionists, the overall focus on the subject was not greatly diminished, and the books were still implicitly evolution based.It has also been suggested that the narrative of evolution's being removed from textbooks due to religious pressure, only to be reinstated decades later, was an example of "Whig history" propagated by the Biological Sciences Curriculum Study, and that the shift in the ways biology textbooks discussed evolution can be attributed to other race and class based factors.In 1958 the National Defense Education Act was passed with the encouragement of many legislators who feared the United States education system was falling behind that of the Soviet Union.