In the late 17th century, Ray had given the first formal definition of a biological species, which he described as being characterized by essential unchanging features, and stated the seed of one species could never give rise to another.
A finais do século XVII, Ray dera a primeira definición formal de especie biolóxica, que describiu como caracterizada por características inmutables esenciais, e afirmou que a semente dunha especie nunca podería dar lugar a outra.