Ilya Ivanov’s early research revolutionised artificial insemination. It allowed one stallion to fertilise up to five hundred mares—natural insemination allowed a maximum of thirty fertilisations. His later experiments were some of the earliest successes in interspecific hybridisation. Ivanov created the guinea pig-mouse and mouse-rat. He experimented with larger species, too, creating the cow-antelope and zebra-donkey. He created the zhorse, a combination of zebra 46 chromosomes and horse 64 chromosomes. We can see why the idea of an apeman might have seemed plausible: humans have 46 chromosomes and chimps have 48.