Reproductive isolation from a cross between a horse and a donkey or between a mare and a donkey, respectively. These animals are nearly always sterile due to the difference in the number of chromosomes between the two parent species. Both horses and donkeys belong to the genus "Equus", but "Equus caballus" has 64 chromosomes, while "Equus asinus" only has 62. A cross will produce offspring (mule or hinny) with 63 chromosomes, that will not form pairs, which means that they do not divide in a balanced manner during meiosis. In the wild, the horses and donkeys ignore each other and do not
Equus (play) Equus (play) Equus is a play by Peter Shaffer written in 1973, telling the story of a psychiatrist who attempts to treat a young man who has a pathological religious fascination with horses. Shaffer was inspired to write "Equus" when he heard of a crime involving a 17-year-old who blinded six horses in a small town near Suffolk. He set out to construct a fictional account of what might have caused the incident, without knowing any of the details of the crime. The play's action is something of a detective story, involving the attempts of the child psychiatrist Dr. Martin