Evolution is the unifying theme of all biology. Living organisms and the interactions between them can be understood most clearly through the lens of evolution; this is reflected in the near-universal acceptance of evolution among biologists (Graffin 2003), who have studied the evidence supporting evolutionary theory and use it to guide their work. However, among the general public, acceptance of evolution is much less prevalent. Despite decades of efforts toward science education reform that might be expected to improve evolutionary understanding and acceptance, little change has occurred in the number of people who accept evolutionary explanations of life’s diversity (Gallup 2014). This rejection of biology’s overarching theme leads to an inability to correctly understand and to reason appropriately regarding biological phenomena (Dobzhansky 1973). In addition, science denial by those responsible for setting policy leads to difficulties in implementation of sound science curricula in schools as well as poor potential outcomes regarding future funding for biological sciences. It is for these reasons and more that a public accepting of evolutionary biology is not only desirable, but necessary. In this study, we attempt to explore how different educational and sociodemographic factors interact with acceptance of evolution in college students.

Knowledge of evolution is perhaps the most intuitive factor related to evolution acceptance. Rutledge and Warden (2000) found that among high school teachers, knowledge of evolution was significantly correlated with acceptance of evolution (see also Deniz et al. 2008; Glaze et al. 2015). This link was also found in an undergraduate sample (Carter and Wiles 2014). Other studies (Heddy and Nadelson 2013; Mazur 2004; Wiles 2014) have found more generally that higher education levels lead to greater acceptance of evolution. Barone et al. (2014) found a significant correlation between knowledge of evolutionary terms and acceptance of evolution among visitors to a natural history museum. However, other researchers have found no significant link between knowledge and acceptance of evolution, especially when other variables are considered in the same model (Cavallo and McCall 2008; Sinatra et al. 2003).

Multiple studies have found an understanding of the nature of science to be significantly related to acceptance of evolution (Carter and Wiles 2014; Cavallo and McCall 2008; Glaze et al. 2015; Johnson and Peeples 1987; Rutledge and Mitchell 2002; Trani 2004). Compared to the more equivocal support of the role of evolutionary content knowledge in evolution acceptance described above, this consistent trend seems to indicate acceptance of evolution might be more strongly influenced by a general understanding of the aims and process of science. Indeed, many of the major creationist criticisms of evolutionary biology stem from a misunderstanding of the nature of science (Matthews 1997; Pigliucci 2008).

Cognitive factors have also been found to have a strong effect on acceptance of evolution. Deniz et al. (2008) found thinking dispositions to be the most significant predictor of evolution acceptance in preservice biology teachers in Turkey. Sinatra et al. (2003) found a measure of epistemological sophistication and a disposition towards actively open-minded thinking to be significantly correlated with acceptance of human evolution (but no relation was found for acceptance of animal evolution). Hawley et al. (2011) found that openness to experience, a psychological metric measuring intellectualism and creativity (John et al. 2008), to be significantly negatively related to acceptance of creationist reasoning. In this study, we consider epistemological sophistication to be a general term referring to a mature manner of understanding the nature of knowledge. Openness to experience is used here as a proxy for epistemological sophistication.

It is generally known that, at least among many Christian denominations in the United States, people who are more strongly religious tend to have greater concern over evolution, especially as it applies to humans. Many authors have found a link between strength of religious convictions and lack of acceptance of evolution (Barone et al. 2014; Carter and Wiles 2014; Glaze et al. 2015; Heddy and Nadelson 2013; Mazur 2004; Moore et al. 2011; Nehm and Schonfeld 2007; Trani 2004), although Hawley et al. (2011) found contradictory results. Religiosity, loosely defined as the degree to which religious faith and conviction have an impact on daily life, is a preferred measure over religious denomination because it indicates a level of religious activity and how strongly religion may influence understandings and decision making.

Combining the factors described above, we present a working model of evolutionary acceptance whereby acceptance of evolution is impacted separately by knowledge of evolution, religiosity, epistemological sophistication, and an understanding of the nature of science. As described previously, all of these factors have been shown to be related to acceptance of evolution. However, very few studies include multiple factors, and to our knowledge, none has quantitatively evaluated their comparative effects simultaneously. To correctly understand the relative impact each factor has, they must be analyzed in a model together, along with demographic variables. This is the aim of our study.

Specifically, we predicted that, when analyzed together in a general linear model, greater epistemological sophistication, evolutionary content knowledge, and understanding of the nature of science will each be associated with higher levels of acceptance of evolution, while higher levels of religiosity will be associated with lower levels of acceptance of evolution.