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) produced as a large-format artist's book by the Old Stile Press, with images and an afterword by the British artist Clive Hicks-Jenkins, in 2009. "Equus" was revived in San Jose, California, in March 2011 at City Lights Theater Company. This production, featuring actors Sean Gilvary as Alan Strang and Steve Lambert as Martin Dysart, received rave reviews. "The Mercury News" labeled Gilvary and Lambert as "haunting," stating Gilvary "...exposing emotions and epidermis, rides bareback in every sense. He gradually manages to make a rather unattractive young creature seem not only sympathetic but redeemable while retaining his hostility and humanity." Starkinsider