Because of efforts to synthesize Greek thought with early Christianity, the Christian church from the beginning of the fifth century to the seventeenth century taught a doctrine of theistic evolution. After a brief return to a belief that Genesis is simple history, Christians from the seventeenth to the nineteenth centuries again waivered from the doctrine of special creation by teaching extreme fixity in created kinds. Close study of the Old Testament today brings out the point that Genesis does teach a fixity of living things. However, the fixity is not at the level of the individual, but at the level of the kind. Thus new individuals are always of the same kind as their parents.