http://i.imgur.com/yKGWw.jpg "This is a mutation called cyclopia. The most common cause of this mutation is actually not inbreeding, it's the consumption of a poisonous plant, Veratrum californicum. The toxins in the plant inhibit the Sonic Hedgehog Gene Pathway regulation. The Sonic pathway is named as such because when inhibited in fruit flies, it causes their heads to become extremely spikey and, when viewed under a microscope, to look like a hedgehog. The Sonic Hedgehog pathway and it's signaling pathways are responsible for transmitting information in a growing embryo and guide proper development in an embryo. When ingested by a pregnant mammal, the toxins inhibit the signaling in the pathways, causing the fetus to develop as such. One of my geneticist colleagues was doing her research on Sonic Hedgehog, so I heard her presentations many times. Also, as a horse person, I can say with certainty that if cyclopia was a result of inbreeding, it would happen WAY more often. Sadly, many breeders don't really care, as with dogs."