The Greeks and Romans did not have a consistent theory of how sex was determined. Pliny the Elder claims that tying the right testicle of a ram will cause him to produce only females, but does not claim this about other creatures. Pseudo-Plutarch lists many Greek theories of sex determination, including heat and cold, left and right testicles, left and right sides of the body, sperm crossing or not crossing from one side of the womb to the other, and the strength or dominance of various body parts.