Previous studies shows that students have difficulty in understanding the evolution of human beings due to difficult conceptions and complexity of the subject. The objective of this research was to study the knowledge of Croatian and Slovenian elementary and grammar school students about human evolution. We wanted to see if there was a difference in knowledge between the students of different countries, genders, and ages. Besides the amount of knowledge, we were interested in whether there exist some characteristic students' misconceptions about human evolution. We have also tried to determine whether there are any background factors associated with cognitive achievements. We conducted a research on 170 students, of which there were 100 primary school students and 70 grammar school students. Research has shown that the knowledge of tested students about human evolution is satisfying. The overall average success on the anonymous test of knowledge was 64,8 %. Slovenian students were better at questions about human evolution than croatian students. We have compared and checked the results that we collected. We can conclude that there are differences in the knowledge of human evolution between students of different countries, and grades. Croatian elementary school students showed more knowledge than Slovenian elementary school students. Slovenian grammar students showed more knowledge than Croatian grammar school students. Slovenian grammar school students showed more knowledge than Slovenian elementary school students, and Croatian grammar school students showed less knowledge than Croatian elementary school students. There are negligible differences in the knowledge of human evolution between the genders. We also found that Croatian and Slovenian students have some characteristic misconceptions that are related to our topic. An analysis of questionnaires has shown that students' knowledge is related to background factors.