European first-year university students accept evolution but lack substantial knowledge about it: a standardized European cross-country assessment

Background: Investigations of evolution knowledge and acceptance and their relation are central to evolution edu‑ cation research. Ambiguous results in this field of study demonstrate a variety of measuring issues, for instance differ‑ ently theorized constructs, or a lack of standardized methods, especially for cross‑country comparisons. In particular, meaningful comparisons across European countries, with their varying cultural backgrounds and education systems, are rare, often include only few countries, and lack standardization. To address these deficits, we conducted a stand‑ ardized European survey, on 9200 first‑year university students in 26 European countries utilizing a validated, com‑ prehensive questionnaire, the “Evolution Education Questionnaire”, to assess evolution acceptance and knowledge, as well as influencing factors on evolution acceptance. even if they are enrolled in a biology‑related study program. Additionally, we developed a multilevel‑model that determines religious faith as the main influencing factor in accepting evolution. According to our model, knowledge about evolution and interest in biological topics also increase acceptance of evolution, but to a much lesser extent than religious faith. The effect of age and sex, as well as the country’s affiliation, students’ denomination, and whether or not a student is enrolled in a biology‑related university program, is negligible. Conclusions: Our findings indicate that, despite all their differences, most of the European education systems for upper secondary education lead to acceptance of evolution at least in university students. It appears that, at least in this sample, the differences in knowledge between countries reflect neither the extent to which school curricula cover evolutionary biology nor the percentage of biology‑related students in the country samples. Future studies should investigate the role of different European school curricula, identify particularly problematic or underrepre‑ sented evolutionary concepts in biology education, and analyze the role of religious faith when teaching evolution.


Introduction
Most experts in the fields of biology (e.g., Dobzhansky 1973) and science education (e.g., Harms and Reiss 2019) agree that evolution is crucial to understanding biology. For this reason, the assessment of acceptance and understanding of evolution is a central topic in science education research (Dunk et al. 2019). Over the last few decades, researchers from various disciplines have investigated knowledge and acceptance of evolution and their mutual relationship between different age groups and education levels (e.g., Clément 2015;Dunk et al. 2017;Fiedler et al. 2019;Ha et al. 2019;Mead et al. 2018;Romine et al. 2017;Sbeglia and Nehm 2018), as well as in the general public (Brenan 2019;European Commission 2005;Hameed 2008; Ipsos Global @dvisory 2011;Pew Research Center 2015).
The discussion of the relationship between acceptance and understanding of evolution is still ongoing because of diverging findings Dunk et al. 2019). For instance, several studies discovered a positive relationship between knowledge about evolution and acceptance of evolution (e.g., Ha et al. 2015;Rutledge and Warden 2000), while others described only weak or even negligible relationships (e.g., Barnes et al. 2017b;Graf and Soran 2010;Torkar and Šorgo 2020). An overview of different empirical findings is available in Fiedler et al. (2019). Some studies that compared different target groups showed that the strength of the relationship is increasing with the level of education (Beniermann 2019;Kuschmierz et al. 2020b).
Although more than 300 articles on acceptance of evolution have been published to date, little consensus has emerged on the primary factors that contribute to this construct . However, some studies found religiosity (Beniermann 2019; Barnes et al. 2019), understanding the nature of science (Graf and Soran 2010;Dunk et al. 2017), or attitudes towards science (Graf and Soran 2010;Großschedl et al. 2014) as predictive factors. Just recently, statistical thinking (Fiedler et al. 2019) and the perception of a personal conflict with evolution (Sbeglia and Nehm 2020) were demonstrated to influence evolution acceptance. In addition, there are some factors whose relationship with acceptance of evolution has only recently begun to be researched, for instance interest in evolution (Barnes et al. 2021a). These differences in research findings reflect the intensely debated measurement issues in evolution education (Beniermann 2019; Barnes et al. 2019;McCain and Kampourakis 2018;Mead et al. 2019;Nehm and Mead 2019;Novick and Catley 2012;, such as the potential for biased results based on the measurement instruments used , neglect of measurement standards , missing definitions of key constructs (Ha et al. 2021b;Konnemann et al. 2012;McCain and Kampourakis 2018), or a sole focus on natural selection while addressing the multidimensional construct of knowledge about evolution (Kuschmierz et al. 2020a). Most research in evolution education has been conducted in the United States (e.g., Miller et al. 2021), while there is comparably scarce empirical data on evolution acceptance and knowledge in Europe (Kuschmierz et al. 2020b).
Europe's situation is very diverse due to different languages, educational systems, and more fragmented research communities (Deniz and Borgerding 2018). Thus, due to a lack of standardized assessment procedures in the existing literature, a comprehensive overview of knowledge about evolution and acceptance of evolution in Europe based on comparable data is still missing (Kuschmierz et al. 2020b).

Methodological issues
Most international comparative surveys measuring acceptance of evolution (Brenan 2019;Hameed 2008;Ipsos Global @dvisory 2011;Miller et al. 2006;Pew Research Center 2015) or knowledge about evolution (European Commission 2005) collected data using only one multiple-choice question with few answer options. These surveys' results may be misleading because of a limited number of answer options (true-false, e.g., in Miller et al. 2006) that forces respondents to choose between few options on a complex topic (Pobiner 2016). Until now, no international comparative study has been performed to compare the state of acceptance of evolution and knowledge about evolution employing a questionnaire, including various multiple-choice questions and rating-scale items (Kuschmierz et al. 2020b).
The distinction between acceptance of evolution and knowledge about evolution in measurement instruments is of crucial importance, since people can have scientifically correct conceptions about evolution but are still not convinced evolution is really happening (McCain and Kampourakis 2018). Another methodological issue is not to distinguish between acceptance of evolution and religious faith (e.g., Clément 2015) because the way in which the relationship of faith, evolution, and creationism is presented influences survey results (Elsdon-Baker 2015; Kampourakis and Strasser 2015).
The sole focus of several of these comparative surveys on human evolution (e.g., in Brenan 2019; Pew Research Center 2015) may lead to another bias as human evolution is known to be harder to accept  and causes higher discomfort (Grunspan et al. 2021;Rughiniş 2011) than evolution of animals and plants. Sbeglia and Nehm (2020) demonstrated that personal conflict with evolution in particular impacts acceptance of human evolution.
Also, definitions of key constructs in previous studies like knowledge, understanding, attitudes, and acceptance are inconsistent and lead to different operationalizations (Ha et al. 2021b;McCain and Kampourakis 2018;. This ambiguous use of terms could be one of the main reasons for partially contradicting results in this field of research (Konnemann et al. 2012;Mead et al. 2019;. For example, 'acceptance' is described as belief, an affective attitude, or a cognitive construct (Konnemann et al. 2012).
' Acceptance of evolution' is the central construct of this work and describes a positive attitude towards evolution (American Educational Research Association 1999). We use the term 'attitude' to describe a connection between an entity (attitude object), and its subjective evaluation (Eagly and Chaiken 1993). Thus, an 'attitude towards evolution' describes personal evaluations about the statement that evolution occurs. A positive attitude towards evolution is called 'acceptance, ' while a negative attitude is called 'rejection' (Ingram and Nelson 2006).
In our terminology, we use the term 'knowledge' instead of the common term 'understanding' because we decided to survey content knowledge. The design of this study (using quantitative methods with a large sample size) is not suitable for measuring understanding. This distinction between terms follows the definition that a "student gains knowledge (via instruction, self-study, etc.) upon which she can build understanding" (Smith and Siegel 2016).

Evolution knowledge and acceptance in Europe
Much research in evolution education has been conducted in the United States (Miller et al. 2021), possibly due to the predominant public opposition to evolution (Brenan 2019) and the long history of creationism in the country (Scott 2008). In contrast, respondents of European countries have shown comparably high acceptance of evolution (European Commission 2005;Miller et al. 2006).
Nevertheless, there are reasons for comparing European countries in a standardized way. Europe's situation is unique because of many countries in geographically little space. Additionally, European countries differ due to different languages, educational systems, and fragmented research communities (Deniz and Borgerding 2018;Kuschmierz et al. 2020b). Thus, investigating differences of knowledge about evolution and acceptance of evolution in Europe based on comparable data offers new insights for the international research community. To date, only few international comparative studies measuring acceptance of evolution or knowledge about evolution in many different countries have been performed in Europe (Clément 2015;Miller et al. 2006). Due to a lack of standardized assessment procedures in the existing literature (Kuschmierz et al. 2020b), previous results should be used with caution when trying to compare European countries as there are several limitations.
The body of existing research on evolution knowledge and acceptance in Europe also varies between both the education levels and the countries. Only in Germany, Greece, and Turkey, more than three studies on knowledge about evolution have been published between 2010 and 2020 (Kuschmierz et al. 2020b). In the same period, only five European cross-country studies on knowledge about evolution have been published, comparing two (Göransson et al. 2020;Graf and Soran 2010;Kralj et al. 2018;Pinxten et al. 2020) to four (Šorgo et al. 2014) European countries. And, there are even less studies (Clément 2015;Graf and Soran 2010) that compared samples from more than one country regarding acceptance of evolution. Between 2010 and 2020, only in four European countries (Germany, Greece, Turkey, and the United Kingdom) three or more studies on acceptance of evolution have been published (Kuschmierz et al. 2020b).
These findings indicate a research gap in Europe in terms of comparable results on evolution knowledge and acceptance in a clearly defined target group.

Relationship of evolution knowledge, acceptance, and religious faith
For decades, the science education research community has investigated how evolution knowledge and acceptance are related to each other and still there is no consensus about this relationship Dunk et al. 2019;Glaze and Goldston, 2015). Whereas some studies reveal a strong (Ha et al. 2015;Rutledge and Warden 2000;Trani 2004), or a moderate to weak positive correlation between these factors Fiedler et al. 2019;Graf and Soran 2010;Großschedl et al. 2014;Ha et al. 2019;Nadelson and Sinatra 2009), other studies report no connection between knowledge and acceptance of evolution (Akyol et al. 2010;Athanasiou et al. 2016;Bishop and Anderson 1990;Sinatra et al. 2003;Tekkaya et al. 2012). However, primary and secondary education students often demonstrated a lacking or weak correlation between acceptance and knowledge (Kuschmierz et al. 2020b), while in most studies pre-and in-service teachers showed a moderate (e.g., Deniz and Sahin 2016) or weak (e.g., Großschedl et al. 2014) positive relationship between these variables.
Previous research in Europe revealed that religious faith and acceptance of evolution are closely related in respondents of various education levels, indicating a lower acceptance with increasing religious faith (Athanasiou et al. 2016;Betti et al. 2020;Clément et al. 2012;Deniz and Sahin 2016;Eder et al. 2011). However, previous research on the relationship between religious faith and acceptance of evolution is limited to few European countries (Kuschmierz et al. 2020b). These studies furthermore indicated differences in acceptance for diverse religious denominations (e.g., Beniermann 2019; Konnemann et al. 2016;Southcott and Downie 2012). A comprehensive European investigation of the relationship between the factors 'knowledge about evolution' , 'acceptance of evolution' , and 'religious faith' as well as the influence of religious denominations and differences between European countries does not exist.

Study goals
The target of this research is to investigate evolution acceptance and knowledge and their relationship using the same standardized measuring method across Europe.
Our results provide information on the state of knowledge and acceptance of European students who have recently completed upper secondary education. Furthermore, this study investigates various predictors for acceptance of evolution. In the discussion, we aim to contextualize the findings by providing an overview of European school curricula regarding the extent to which they cover evolutionary biology (Additional file 2).

Research questions
1. What is the level of knowledge about evolution, acceptance of evolution, and religious faith in European first-year university students in biology and non-biology programs? 2. What is the relationship of knowledge about evolution, acceptance of evolution, and religious faith in European first-year university students in biology and non-biology programs? 3. What are the main factors influencing acceptance of evolution in European first-year university students?

Research instrument
For the purpose of this study, we used parts of the "Evolution Education Questionnaire (EEQ)" (Beniermann et al. 2021b) which has been designed to assess acceptance of evolution, knowledge about evolution, and religious faith. Specifically, we analyzed the subscales KAEVO-A (Kuschmierz et al. 2020a), ATEVO (Beniermann 2019), and PERF (Beniermann 2019) of the EEQ. Unlike most instruments in this field of research (Kuschmierz et al. 2020a)-these have been validated in the European context based on standards for educational and psychological testing (American Educational Research Association 1999), as discussed in the "Validity and reliability" section. Categories to enable the standardized interpretation of the results are available for all three instruments (Beniermann et al. 2021b;Kuschmierz et al. 2020a).

Knowledge about evolution
The Knowledge About Evolution 2.0 instrument (KAEVO 2.0; Kuschmierz et al. 2020a) covers the most essential evolutionary topics, including microevolution and macroevolution. This version, and also its predecessor KAEVO 1.0, were used to measure knowledge about evolution in previous studies (KAEVO 1.0; Beniermann 2019, KAEVO 2.0; Kuschmierz et al. 2020a, Torkar andŠorgo 2020). The instrument consists of three sections (A, B, and C). KAEVO-A was utilized in this paper and contains 12 multiple-choice items on evolutionary adaptation and natural selection (four items), biological fitness (one item), speciation including variation (two items), the heredity of phenotype changes (two items), human evolution (one item), and phylogenetic tree reading (two items). All of these items consist of a question (e.g., "How did the ability to run fast evolve in cheetahs?") embedded in a scenario, followed by several answer options. The answering options contain distractors that reflect common misconceptions, as well as the scientifically correct option. We dichotomized the items of KAEVO-A (correct = 1; wrong/not known = 0) to generate sum scores for the analyses (score range: 0-12). According to our definition of the construct 'knowledge about evolution' , a higher score means a greater knowledge about evolution.

Acceptance of evolution
The Attitudes Towards Evolution scale (ATEVO; Beniermann 2019; Beniermann et al. 2021b) is a five-point rating scale with eight items. Each item consists of a statement (e.g., "In my personal opinion, the animals and plants we know today have developed from earlier species. ") and the five answer options are "agree", "somewhat agree", "undecided", "somewhat disagree", and "disagree. " Answers are quantified by values from 1 (absolute rejection of evolution) to 5 (absolute acceptance of evolution). Total scores range between 8 (absolute rejection of evolution) and 40 (absolute acceptance of evolution) (Beniermann et al. 2021b). This is in accordance with our previous definition of the construct 'acceptance of evolution. ' To ensure content validity of the ATEVO experts from different fields have reviewed and evaluated the items (Beniermann 2019). Pre-tests with high school and university students were conducted to ensure the validity of the answer processes (American Educational Research Association 1999). Evidence for local validity and reliability for the ATEVO scale was shown based on four studies (n total = 9311; Beniermann 2019). Survey populations differed in the four studies to ensure that the ATEVO scale is a suitable instrument to measure attitudes towards evolution for the general public and groups of various ages and education, as well as explicitly non-religious or religious people. In order to address these diverse groups, the ATEVO scale includes items on evolution of plants and animals as well as items with a focus on human evolution that are known to be harder to accept ). This approach is especially useful when surveying the partly rather secular samples from different European countries (Beniermann et al. 2021b).

Religious faith
The Personal Religious Faith scale (PERF; Beniermann 2019; Beniermann et al. 2021b) is a five-point rating scale with ten items. Each item consists of a statement (e.g., "I feel that God exists. ") and five answer options from "agree" to "disagree". Answers are quantified by values from 1 (not religious) to 5 (very religious), while total scores range between 10 (not religious) and 50 (very religious) (Beniermann et al. 2021b). The PERF scale, based on the same measurement standards and procedure as described above for the ATEVO scale, produces valid and reliable results (Beniermann 2019). It was created to measure religious faith independent from the respondents' denomination (Beniermann 2019).

Additional factors
In addition to the three main scales of this study, participants had to provide information on their age, sex, interest in biology as well as their denomination. Interest in biology was measured with a rating scale item. Participants were asked to rate their individual interest in biology on a 7-point scale from "very low" to "very high". To indicate their denomination, participants were asked to choose one of the following: Orthodox, Catholic, Christian free churches, Protestant, Muslim (Sunni, Alevi, or Shiite), Jewish, Hindu, Buddhist, Other, or None.

Sample
We aimed for a broad sample of European University students, including as many European countries as possible, to cover the diversity of Europe. In order to handle the varying total numbers of students in different European countries, a minimum sample size of n = 150 was negotiated with stakeholders in smaller European countries. As a stratified sampling strategy was not possible due to practical reasons of the national stakeholders, we applied a convenience sampling strategy to also include small European countries as well as less research-intensive countries.
In total, 11,723 first-year university students from 26 European countries voluntarily participated in the study. We chose first-year university students who had recently finished upper secondary education to generate a comparable target group. To learn about the status of knowledge about evolution and acceptance of evolution of students after finishing secondary education in Europe, first-year university students are a suitable sample that is easy to access. The alternative option to survey high school students was not feasible, since the access was not possible in all countries, for instance because high school students have to take important exams in the last weeks of school. Surveying high school students would have decreased the sample size and the number of participating countries substantially.
We excluded all participants who were not enrolled in the first semester, were older than 25 years or graduated from upper secondary education more than 2 years before the survey. Additionally, participants who spent 2 or more years in a country other than the surveyed country while in upper secondary education were excluded before the analyses. The resulting sample size after exclusion was 9200 (see Fig. 1). We targeted students enrolled in a biology-related university program but also surveyed non-biology students for comparison (list of biologyrelated university programs in Additional file 1).

Data collection
The English version of the instrument was translated into the participating countries' local languages-23 in total. We ensured the translations' quality by reverse translation of the questionnaire via national experts in the field of biology or biology education. The data were collected at European universities (N = 84) at the beginning of the respective semesters/terms. We used a paper-pencil format because we wanted the voluntary respondents to fill the questionnaire in a standardized way in class, lasting about 30 min. The students were supervised while filling out the questionnaire and could not search the internet for the correct answers (in terms of knowledge about evolution) or let others fill out the questionnaire for them. The complete test process was anonymous, and the questionnaire was voluntary; the respondents received no incentives for completing it. Employing uniform survey instructions, the people handing out the questionnaires to students received clear instructions for the respondents, including not to communicate with the respondents beyond the instructions.
For data analysis, we separated the biology-related and non-biology students. This made it possible to compare the results of the respective subgroups in different European countries.

Overviews of the subject 'Biology' and the topic evolution in the European school curricula
To discuss the results in context and to give additional information to international readers, we reviewed the national school curricula concerning the subject "Biology" of the participating European countries, focusing on the teaching of evolution (see Additional file 2). We then summarized whether and to what extent evolution Fig. 1 Sample overview per country. Corrected sample size per country (n after excluding cases, see the "Materials and methods" section for exclusion criteria). Pie charts show the percentage ratio of biology-related to non-biology students per country. Countries in grey are not part of the study is taught in lower and upper secondary level and which evolutionary concepts are covered.

Statistical analyses
All statistical analyses were conducted in RStudio (Version 1.3.107 based on R Version 4.0.2). The dataset (Additional file 3), as well as the R-Script (Additional files 4, 5 and 6), can be assessed in the additional information.
In the first step of the data cleaning procedure, we excluded 234 observations from the data set, all belonging to three Spanish courses that were not provided with the questions regarding their religious faith.
With the remaining data set (n = 9200), a missing value analysis was conducted. The percentage of missing values across the 41 items varied between 0 and 7.2%. In total 6579 observations were complete (71.5%). Another 1235 observations had only one missing value (13.4%), which, after further analyses, we assumed to occur completely at random. In contrast, 559 participants (6.1% observations) had not answered any questions concerning their religious faith, despite being provided with the complete questionnaire. We assumed a systematic pattern of missing values for this.
Considering the missing value analysis results, we decided to include all available descriptive studies and scale comparison. Furthermore, we utilized a complete case approach to perform multilevel analyses. Also, we applied the predefined exclusion criteria to filter the original dataset, setting a minimal sample size per country (n = 150) to enable statistical analyses in which subgroups are compared (e.g., students of different countries). Six of 26 countries were excluded from the multilevel analyses because the sample size was too small (see countries marked in yellow in Fig. 1). We reported the specific sample size for each analysis.
Mean scores and standard deviations for the three main scales were computed for the entire sample and depending on the country, university program, and sex. To compare the mean scores of knowledge about evolution, acceptance of evolution, and religious faith between students who enrolled in a biology-related university program and students who enrolled in another program, three separate t-tests were computed, each based on a mixed model using the country as a random effect and Satterthwaite approximation. The effect size was reported as the difference in explained variance (Aiken et al. 1991). In addition, bivariate correlations for the whole sample were used to describe the relationship between the main scales.
To compare the distributions of the sample values for acceptance of evolution, knowledge about evolution, and religious faith in the whole sample, we rescaled from the original values of the main scales to an artificial scale, ranging from 0 to 100, using the following equation: Due to our data's hierarchical structure-students are nested in courses at universities within countries-we decided to use a multilevel modeling approach to investigate the relationship between acceptance of evolution and other variables in this dataset. However, the university-specific and country-specific sample sizes are sometimes limited, and multilevel regression models require a certain number of higher-level-units to produce unbiased parameter estimates (McNeish and Stapleton 2016;Snijders 2005). Therefore, we decided to consider only two levels: students as individual observations nested within countries.
We specified an intercept-only model as the null model and five models with an increasing number of fixed effects: Model 1 (sex and age), Model 2 (+ university program and interest in biology), Model 3 (+ knowledge about evolution), Model 4 (+ religious faith), and Model 5 (+ denomination). Additionally, the country was included in each model as a random intercept. The intercept-only model's intraclass correlation coefficient (ICC) was 0.11, which means that 11% of the overall variance can be accounted to country-specific effects (χ 2 (1, N = 6227) = 520.65, p < 0.001) and a multilevel modeling approach is appropriate (Maas and Hox 2005).
All models were estimated using the maximum likelihood method (r-Package: lme4; Bates et al. 2015). Parametric bootstrapping (number of samples: 10,000) was applied to obtain confidence intervals for both the parameter estimates of the fixed effects and the variance components. Due to the listwise deletion procedure, all models were estimated with a sample size of n = 6227 level-1 units (students) and n = 20 level-2 units (countries). Using the same sample for all models allowed us to compare the models directly via likelihood-ratio tests. Additionally, we evaluated and compared the models based on their Akaike information criterion (AIC), Bayesian information criterion (BIC), and Pseudo-R 2 values. A decrease in AIC and BIC between two subsequent models indicates a better fit of the latter. R 2 m (marginal) represents the proportion of variance explained by fixed factors. R 2 c (conditional) represents the proportion of variance explained by both fixed and random factors (Johnson 2014; Nakagawa and Schielzeth 2013).
We tested the models for multivariate normality of their residuals, as well as for homoscedasticity and multicollinearity. Multicollinearity was not an issue, as the explanatory variables' VIF values ranged between 1 and 1.4. However, the residuals' distribution was significantly left-skewed, and visual analyses of the quantile-quantile-plots (QQ-plots) indicated heteroscedastic residuals due to a ceiling effect. We used the package "robustlmm" (Koller 2016) and a Design Adaptive Scale approach to obtain robust parameter estimates and evaluate if the models' parameter estimates vary significantly from the initial non-robust models. We found minimal variations in the parameter estimates and reasonably narrow confidence intervals of the nonrobust models' parameter estimates. Thus, we decided to report the results of the initial models. Our initial plan was to account for interactions between the explanatory variables and allow the regression slopes for religious faith to vary randomly in two additional models.
As both models either did not converge properly (random slope model) or yielded biased parameter estimates due to multicollinearity (interaction model with VIF scores above 5), we decided to exclude them from the results.

Validity and reliability
All elements of the EEQ instrument have been validated in an iterative process, and evidence for validity and reliability has been provided in previous studies (Beniermann 2019;Kuschmierz et al. 2020a).
In addition, the KAEVO instrument has been introduced with a four-dimensional structure for KAEVO-A (Kuschmierz et al. 2020a). Factor analysis for the present study sample confirmed this structure.
In previous studies (Beniermann 2019), the ATEVO scale has shown a unidimensional or two-dimensional structure for different samples. Principal Axis Factoring (PAF) for ATEVO and PERF revealed appropriateness to treat each of them as unidimensional (Field 2009; see Table 1).
We tested evidence for the reliability of the scales via internal consistency. The PERF scale produced very high Cronbach's alpha values for the entire sample (α = 0.969) and all single countries. The ATEVO scale had a high value for the whole sample (α = 0.739) and acceptable-to-high values for the single countries ( Table 2).
The KAEVO instrument contains several underlying constructs, which is why Cronbach's alpha is not appropriate to measure the reliability of the entire instrument (Kuschmierz et al. 2020a).

Results
European first-year university students generally accepted evolution but lacked substantial knowledge about evolution. Moreover, students also varied much more in their knowledge about evolution and religious faith than in their acceptance of evolution Within the investigated sample, first-year university students across Europe rather accepted evolution   Table 3). Biology-related students accepted evolution slightly more (M = 32.52, SD = 4.86; see Table 3) than nonbiology students (M = 31.28, SD = 5.01; score range: 8-40; see Table 3) but the effect size was negligible (t(7835.83) = − 8.30, p < 0.001, f 2 = 0.01). A small number of students rejected (0.39%) or rather rejected (0.95%) evolution (according to the suggested categories in Table 4).
In contrast, students generally lacked significant knowledge about evolution, evidenced by the fact that, on average, they answered less than half of the questions in a scientifically accurate manner (M = 5.06, SD = 2.57; score range: 0-12; see Table 3). Students that were recently enrolled in a biology-related university program knew significantly more about evolution (M = 5.53, SD = 2.54; score range: 0-12; see Table 3) than new non-biology students (M = 3.85, SD = 2.22; score range: 0-12; see Table 3), with a medium effect size (t(7799.74) = -− 8.93, p < 0.001, f 2 = 0.05). However, even within the group of biology-related students, many demonstrated very low (47.4%) or low (27.1%) knowledge about evolution (see Table 4).
We used scaled values to standardize the different score ranges and visualize the distribution of responses (see Fig. 2). Comparing these distributions illustrated clear differences between acceptance of evolution, knowledge about evolution, and first-year university students' religious faith. Whereas few students did not accept evolution in both subgroups, the scope of knowledge about evolution was broadly distributed. The two subgroups differed most regarding their knowledge about evolution. Students with high and moderate religious faith were equally represented in the biology-related subgroup, while most students were not religious. Non-biology students with high, moderate, and low religious faith also roughly balanced each other. Still, compared to the biology-related students, there were fewer students who are not religious.    Page 10 of 22 Kuschmierz et al. Evolution: Education and Outreach (2021) 14:17 Students with a lower acceptance of evolution also showed less knowledge about evolution but higher religious faith.

Knowledge and acceptance were only weakly related
In our sample, acceptance of evolution (ATEVO score) and religious faith (PERF score) showed significantly negative correlations with a moderate effect.
At the country level, the samples did not differ much in acceptance of evolution but varied much more in knowledge about evolution and religious faith (see Fig. 4). Finland (100% bio-related students), the Netherlands (100% biology-related students), and Spain (94.8% biology-related students) showed the highest scores in knowledge about evolution (see Fig. 4). Furthermore, in 19 of 26 countries, students answered less than half of the questions on knowledge about evolution correctly (see Table 5).

Among European first-year university students, the country of residence had only a minimal impact on acceptance of evolution. In addition, the extent of religious faith influenced acceptance of evolution much more than knowledge about evolution
A multilevel modeling approach was used to account for variations in acceptance of evolution between students (Level 1) and countries (Level 2). The following explanatory variables were added sequentially: age, sex, enrollment in a biology-related university program (yes/no), Page 11 of 22 Kuschmierz et al. Evolution: Education and Outreach (2021) 14:17 interest in biological topics, knowledge about evolution, religious faith, and denomination (see Table 6).
Overall, Model 4, which included the explanatory variables age, sex, enrolled in a biology-related university program, interest in biological topics, knowledge about evolution, and religious faith, provided the best model fit. It explained significantly more variance in acceptance of evolution (23%) than all previous models. In Model 4, 19% of the explained variance could be attributed to the explanatory variables. The largest proportion of variance explained could be attributed to religious faith, as Model 4 explained 11% more variance than Model 3 (χ 2 (1, N = 6227) = 611.62, p < 0.001).
The model showed that very religious students accepted evolution significantly less than non-religious students. Furthermore, with each unit increase on the religious faith scale, the acceptance of evolution score dropped by 0.12 units (b = − 0.12, p < 0.001, 95% CI [− 0.12, − 0.11]).
Also, there was a significant relationship between knowledge about evolution and acceptance of evolution (b = 0.24, p < 0.001, 95% CI [0.19, 0.29]), indicating that students who knew more about evolution also tended to accept evolution more.
The increase in variance explained by adding knowledge about evolution in Model 3 was 4% (χ 2 (1, N = 6227) = 169.81, p < 0.001). The decrease of the parameter estimate for knowledge about evolution between Model 3 and Model 4 indicated that some of the variance explained by knowledge about evolution may be related to the extent of the students' religious faith.
Acceptance of evolution by students increased with their interest in biological topics. An increase in interest in biological topics by one unit accompanied an increase in acceptance of evolution by 0.32 units (b = 0.32, p < 0.001, 95% CI [0.23, 0.41]). As a variable, interest in biological topics seemed to be more or less independent from the other investigated explanatory variables, and its estimated effect was rather stable across all models. Whether a student enrolls in a biology-related university program was not a significant predictor for acceptance of evolution (Model 4). Model 2 showed that students enrolled in a Fig. 3 Relationships between knowledge about evolution, acceptance of evolution, and religious faith. Scores (for each student) for knowledge about evolution (KAEVO score range: 0-12), acceptance of evolution (ATEVO score range: 8-40), and religious faith (PERF score range: 10-50) are displayed. Low scores correspond to low knowledge, low acceptance, and low religious faith. r ATEVO-PERF = − 0.37**, n = 8032; r KAEVO-PERF = − 0.36**, n = 7260; r KAEVO-ATEVO = 0.29**, n = 7434; **Correlation is significant at the 0.01 level (2-tailed) biology-related study program tended to accept evolution more than students enrolled in a non-biology program. However, when adding knowledge about evolution to the model, the effect of the students' program decreased (Model 3).
Female students accepted evolution significantly less (b = − 0.59, p < 0.001, 95% CI [− 0.84, − 0.35]) than male students for all models. However, the effect's strength decreased when adding the variables knowledge about evolution (Model 3) and religious faith (Model 4). This indicated that some of the variances in acceptance of evolution between men and women could be accounted for by sex differences in knowledge about evolution and religious faith rather than sex itself. As expected in this age-homogeneous target group (see exclusion criteria in the "Sample" section), age was not a significant predictor across all four models.
In the best-fitting Model 4, a country's affiliation explained variance dropped to 5% (ICC = 0.05). This may indicate an interaction between the Level-1 and Level-2 explanatory variables. As our study's focus was confined to individual explanatory variables on acceptance of evolution and not country-specific factors, we did not gather additional information.

Within the group of European first-year university students, country affiliation plays only a minimal role in accepting evolution
We provided the first standardized comparative analysis on the state of evolution knowledge and acceptance in Europe and the role of the country affiliation based on a clearly defined and comparable target group. For the first time, to our knowledge, European students were surveyed regarding their evolution knowledge and acceptance using the same multidimensional measuring instrument. Our results show that European first-year university students mostly accept evolution. The country affiliation plays only a minimal role in explaining acceptance or rejection of evolution. These two findings indicate that most of the European education systems for upper secondary education with all their differences lead to acceptance of evolution at least in university students. So far, studies showed varying results, depending on the used instrument or the surveyed country. Results of some previous studies on university students of different European countries are supported by our findings (Arthur 2013;Beniermann 2019;Betti et al. 2020;European Commission 2005;Gefaell et al. 2020;Graf and Soran 2010;Großschedl et al. 2014;Konnemann et al. 2018;Nehm et al. 2013;Southcott and Downie 2012). However, other studies revealed undecided positions or rejection of evolution among pre-service teachers in Greece  and Turkey (Akyol et al. 2010Bilen and Ercan 2016;Deniz et al. 2011;Deniz and Sahin 2016;Graf and Soran 2010;Irez and Bakanay 2011;Yüce and Önel 2015). In the present study, Greek and Turkish students mainly accept evolution, with several other countries showing less acceptance (see Fig. 4). However, the Turkish results should be interpreted with caution because of the small sample size (n = 85). Still, our comparison of 26 European countries reveals that country affiliation plays only a minimal role in explaining acceptance or rejection of evolution.
Within our extensive European sample of first-year university students, a very small share of students rejects or rather rejects evolution based on the interpretation categories (see Table 4). These students that reject evolution could be the focus of further analyses and studies. By focusing on this group, researchers could investigate the reasons for rejection in more detail and compare predictors for acceptance of evolution with the whole sample. In summary, only a minimal number of European firstyear university students reject evolution.  Kuschmierz et al. Evolution: Education and Outreach (2021) 14:17 European first-year university students, even those enrolled in biology-related programs, often lack knowledge about evolution The extent of knowledge about evolution is much more varied than in the case of acceptance in the investigated sample. The vast variance in knowledge is especially remarkable because the participants are homogeneous in age and educational level since they all just finished secondary education in their respective countries. Even among the students enrolled in a biology-related university program, the level of knowledge varies greatly (see Fig. 2); however, all students were surveyed before they were taught evolution at university. Previous studies found that knowledge about evolution among European university students generally increases with biology education (Kuschmierz et al. 2020b). However, some studies show low levels of expertise even for biology-related university students in Europe (Kuschmierz et al. 2020a;Pinxten et al. 2020). This disparity in the literature is supported by our results, as biology-related students knew significantly more about evolution than non-biology students, albeit the level of knowledge among biology-related students was not as high as one might expect in most countries. Additionally, the country samples differed much more in evolution knowledge than in evolution acceptance. This was true even within the biology-related students, though none had received evolution education at university previously. This effect may be explained by the varying coverage of evolution in national secondary school curricula. Before entering upper secondary education, students of almost all of the 26 surveyed European countries had been taught about evolution to some extent (Additional file 2). However, students graduating from upper secondary schools in Cyprus, Portugal, and Turkey may not have ever been taught evolution. Furthermore, during upper secondary education, differences between European countries can be found in the curricula. In some European countries, including France, Germany, the Netherlands, and Slovenia, whether students are taught about evolution, and to what extent, depends on the path they choose in secondary education. In other countries, such as Finland and Serbia, evolution is part of all students' curriculum.
Almost all surveyed students from Finland, the Netherlands, and Spain were enrolled in a biology-related study program, which may explain the high knowledge scores. Whereas evolution is compulsory in grades seven to nine in Finland, it is an elective topic for students in Spain and the Netherlands. In Latvia (96.6% biology-related students), where the students had the lowest scores in knowledge about evolution, the amount of evolution lessons is similarly dependent on students' choices. In the Czech Republic (100% biology-related students), where the students also had low scores in knowledge about evolution, students entering university usually attended compulsory evolution classes in upper secondary education. In Slovakia (95.9% biology-related students), evolution classes are also required in upper secondary education; however, evolution is not a central theme in biology education (for information on the school curricula, see Additional file 2). In our Slovakian sample, students also showed low scores in knowledge about evolution.
Hence, it appears that the differences in knowledge between countries reflect neither the number of evolution lessons in the respective school curricula nor the share of biology-related students, at least not for the national samples included in the analysis (national sample size n ≥ 150).
However, we cannot exclude the possibility that knowledge differences are related to the structure of national school curricula since we did not investigate the number of evolution lessons the students had and how evolution was addressed during their school career. Further studies should focus more on the relationship between evolution lessons during secondary education and knowledge about evolution. Additionally, the integration of evolution in school curricula regarding the specific topics addressed and concrete learning goals should be investigated. This would help to better understand what students in different countries learn about evolution and how this impacts their knowledge about evolution. Moreover, knowledge acquisition in evolution is crucially dependent on biology teachers' content knowledge as well as pedagogical content knowledge (Kuschmierz et al. 2020a). Therefore, pre-service biology teachers' educational training should be studied as a factor in student knowledge about evolution in future research, as it differs substantially between European countries (Evagorou et al. 2015). Furthermore, there may be barriers to teach evolution in school similar to those identified for higher education (Tolman et al. 2021). These have to be taken into account as well as potential difficulties in diagnosing student's misconceptions (Fischer et al. 2021).

Religious faith predicts acceptance of evolution much more than knowledge about evolution and students' denomination
Our results revealed a positive but rather weak relationship between evolution knowledge and acceptance. Previous studies in single European countries varied from no connection between these two constructs (Akyol et al. 2010;Athanasiou et al. 2016;Graf and Soran 2010;Tekkaya et al. 2012;Torkar and Šorgo 2020), to a weak Graf and Soran 2010;Großschedl et al. 2014;Nehm et al. 2013) or moderate (Buchan 2019;Deniz and Sahin 2016;Großschedl et al. 2018;Mantelas and Mavrikaki 2020;Stanisavljevic et al. 2013) positive relationship. Furthermore, we found a negative correlation with a moderate effect between the religious faith and acceptance of evolution, which was also identified in previous studies across Europe (Annaç and Bahçekapılı 2012;Beniermann 2019;Betti et al. 2020;Deniz et al. 2011;Deniz and Sahin 2016;Graf and Soran 2010;Southcott and Downie 2012).
In our study, religious faith influences acceptance of evolution much more than any other factor tested, including knowledge about evolution. Although religious faith alone cannot sufficiently explain the rejection of evolution (Beniermann 2019;McCain and Kampourakis 2018), it plays a vital role as a predictor within the group of students that identify as somewhat religious. It was shown that religious faith predicts the level of evolution acceptance for religious people regardless of other factors that have been shown to influence evolution acceptance for other samples (Allmon 2011;Rissler et al. 2014). The interaction of science and religion is a very sensitive issue, and instructors are often reluctant to discuss this topic with their students (Barnes and Brownell 2016;Southerland and Scharmann 2013). However, especially in rather religious regions, evolution education highly benefits from a cultural sensitivity and awareness of instructors (Barnes and Brownell 2017). One way to accomplish this is the use of the Religious Cultural Competence in Evolution Education framework (Barnes and Brownell 2017) that in particular addresses the competence to bridge cultural differences and enable effective communication with students with other cultural backgrounds than the instructor's. This approach might increase acceptance of evolution by reducing the perceived conflict between religion and evolution (Barnes and Brownell 2017), as this perceived conflict was demonstrated to impact evolution acceptance (Barnes et al. 2021b;Sbeglia and Nehm 2020). Moreover, addressing the compatibility between evolution and religion (Barnes et al. 2017a;Southerland and Scharmann 2013;Yasri and Mancy 2016), for instance, by referring to religious authorities and role models when teaching evolution (Holt et al. 2018;Mead et al. 2017), could reduce the students' conflict between these two topics. Thus, to foster evolution acceptance during teaching and increase the level of knowledge about evolution, teachers should be enabled to discuss the relationship between evolution and religion with their students and avoid the assumption that people, who accept evolution, are necessarily atheistic because it is associated with lower evolution acceptance for religious persons (Barnes et al. 2020). This might support learners to develop the competence to make sound judgments about the compatibility of evolution and religion (Mead et al. 2018).
It was previously shown that acceptance of evolution differs between denominations for university students in Austria, Germany, and the UK. Students without a denomination showed the highest scores (Beniermann 2019;Konnemann et al. 2016;Lammert 2012), while Christian Free Churchers (Beniermann 2019;Konnemann et al. 2016) and Muslims (Eder et al. 2011;Fenner 2013;Lammert 2012;Southcott and Downie 2012) showed the lowest scores. In agreement with those findings, in our study, Muslims accepted evolution significantly less than students without a denomination. In contrast to previous studies, however, Christian Free Churchers did not accept evolution significantly less than non-affiliated students, while Protestants showed significantly lower acceptance towards evolution. The different meanings of Free Churches as organizational structures across Europe (Elwert and Radermacher 2017) could explain this or because fundamental Evangelical religious practices are represented within Protestant communities in many European countries (Elwert and Radermacher 2017). However, the model fit decreased when adding denominations, indicating that denomination per se is not a significant predictor for accepting evolution, at least not in our sample. This finding agrees with previous studies, which revealed that the observed differences in acceptance of evolution between countries are mostly due to national socio-cultural background rather than denomination (Clément et al. 2012;Clément 2015).
In this sample, students' acceptance of evolution increased with their interest in biological topics. Although it is known that interest can foster the motivation to learn a topic (Harackiewicz et al. 2016;Hidi and Harackiewicz 2000), there is very little research on the interest in evolution (Barnes et al. 2021a;Ha et al. 2012a). In a previously conducted study, Korean and US biology majors and non-majors college students were assessed on acceptance of evolution, knowledge about evolution, interest in evolution, and religiosity (Ha et al. 2012a). Korean college students showed higher knowledge about evolution and acceptance of evolution but lower religiosity and interest in evolution as US college students. This finding seems to contradict our finding that interest in evolution increases with accepting evolution. However, the role of interest for accepting evolution should be the focus of future studies.
Within the investigated sample, female students accept evolution less than male students. This is consistent with previous findings that showed the differences in acceptance of evolution are most likely related to the different degrees of religious faith between women and men (Beniermann 2019). However, in a recent study on Greek biology university students, differences in evolution acceptance between genders were observed even after controlling for religiosity (Mantelas and Mavrikaki 2020). Although the gender gap in religious faith is well known and consistent across Western countries and especially Christian cultures (Pew Research Center 2016;Sammet 2017), the existence of a gender gap in evolution acceptance and possible rationales could also be the focus of future studies.

Limitations
We acknowledge limits to our data's generalizability due to the differences in sample sizes and shares of biologyrelated and non-biology students within the surveyed countries. Even though our samples are not representative of single countries, our findings still offer added value. The large total sample size and the standardized comparison basis provide essential insights into European first-year university students' acceptance and knowledge about evolution. In contrast to other comparative surveys (Brenan 2019;Ipsos Global @dvisory 2011;Miller et al. 2006;Pew Research Center 2015), we gathered data with the same validated instrument, including various multiple-choice questions.
The research instrument was translated into 23 languages to be able to survey the respondents in their native language and the translation process is a source of potential bias, which we addressed by retranslating the questionnaire with the help of national experts in the field of biology or biology education. For translations in the future, we recommend using the Translation-Review-Adjudication-Pre-test-Documentation (TRAPD; European Social Survey 2014) method. This method enables the reliable identification of problematic translations (Harkness 2003).
Each subsequent model in our multilevel model analysis explained more variance in acceptance of evolution than the previous model. This suggests that more predictors could have been added to the model, such as socio-cultural factors and the 'nature of science understanding' (Akyol et al. 2010;Graf and Soran 2010;Nelson et al. 2019), 'trust in science' (Graf and Soran 2010;Großschedl et al. 2014), perceived personal conflict with evolution (Sbeglia and Nehm 2020) or statistical thinking (Fiedler et al. 2019) that have been shown to interact with acceptance of evolution.
In terms of knowledge about evolution, we are limited to the evolutionary concepts covered in the study's questionnaire: evolutionary adaptation and natural selection, biological fitness, speciation, including variation, the heredity of phenotype changes, human evolution, and tree reading. When relating knowledge about evolution to the school curricula of the respective countries, it should be noted that the educational outcomes defined in the school curricula do not necessarily reflect actual knowledge about evolution gained by average students and must be interpreted with caution. Additionally, many other factors influence educational outcomes, such as teachers' experience and knowledge of general biology, and, in particular, evolutionary biology.

Conclusions
Our results showed that country affiliation only plays a minimal role in acceptance of evolution among European first-year university students, despite the varying cultural backgrounds and education systems. It would be interesting to extend these analyses beyond a clearly defined target group to a broader sample group to determine if our results can be confirmed on a greater scale. Additionally, further investigations should focus on the limited knowledge about evolution among students in Europe and potential gaps in school curricula regarding specific evolutionary topics. Our results suggest that merely increasing the number of evolution lessons may not be effective as this is not crucial for improving students' knowledge about evolution. A more detailed and standardized comparative analysis of the European school curricula could reveal potential differences, for instance, in terms of evolutionary concepts covered and specific learning goals. By analyzing our results in the context of the respective national school curricula concerning evolution (Additional file 2), we investigate potential correlations between national school curricula and evolution knowledge and acceptance. With the recently published "FACE" (Framework to Assess the Coverage of biological Evolution by school curricula; Sá-Pinto et al. 2021b), a tool for analyzing curricula, European school curricula could be analyzed and subsequently collated with our results. Furthermore, an in-depth investigation of results concerning knowledge about particular evolutionary concepts (e.g., evolutionary adaptation and tree reading) could reveal concept-dependent difficulties in understanding that should be covered explicitly in class. Moreover, in-class activities (e.g., Sá-Pinto et al. 2021a) could also be helpful to foster the understanding of evolution.
Our finding that religious faith predicts acceptance of evolution much more than knowledge about evolution implies that, besides increasing knowledge about evolution, emphasis should be placed on the relationship between evolution and religion when fostering evolution acceptance, for instance through approaches with emphasis on reasoning and argumentation (Beniermann et al. 2021a). However, instructors are often reluctant to address this sensitive topic; thus, teaching validated modules of high didactic quality and acknowledging challenges in understanding as well as fostering cultural competence (Barnes and Brownell 2017) could reduce