Difficulties in understanding evolution are often rooted in early childhood, arising from naïve assumptions and cognitive biases. However, literature reviews mainly focus on school and university students' understanding of evolution, with only limited comprehensive reviews on children in early childhood aged up to 7 years. This systematic review aims to capture precursory concepts in evolution and influencing cognitive biases as documented in the empirical literature. Searches of three databases identified 204 articles, of which 26 were used for further analyses after screening for eligibility. The analyses revealed that even young children are capable of understanding the basic mechanisms of core concepts in evolution, such as variation, inheritance, and natural selection. However, while children's understanding of the inheritance concept has been investigated intensively, their understanding of variation lacks in-depth research despite its probable influence on natural selection. Existing evidence is contradictory concerning the usefulness of children's cognitive biases for learning core concepts in evolution: These can serve as stepping stones for learning evolutionary principles, but their usefulness is questioned if children have already developed scientifically correct explanations. More research is clearly needed concerning the reciprocal effects of children's precursory core concepts in evolution in order to develop effective learning interventions for children.