The Fascinating Phenomenon of Animals With Multiple Heads

Polycephaly is a rare and fascinating phenomenon where an animal is born with more than one head. The term comes from the Greek words 'poly' meaning 'many' and 'kephale' meaning 'head.' It primarily occurs because identical twins fail to separate completely, resulting in conjoined twins. While cases are reported across various species, from snakes and turtles to cows and pigs, it's most often recognized in snakes and turtles. Strikingly, these animals can lead relatively everyday lives, with each head controlling its part of the body. For instance, a two-headed snake named We was auctioned in 2006. Living six years is quite an achievement for polycephalic animals as they generally suffer from health issues. The condition is scarce in human beings, but there have been documented cases. The most famous are perhaps Chang and Eng Bunker, Thai-American conjoined twin brothers whose condition and birthplace led to the term 'Siamese Twins'. The mechanism behind polycephaly isn't completely understood yet. It's generally accepted that it results from a delay or disruption in the twinning process - when one fertilized egg splits into two embryos. Scientists continually study this anomaly for insights into developmental biology. Polycephalic organisms pose complex neurological questions: if there are two brains, which controls behavior? How do they co-ordinate? Despite its scientific significance, polycephaly remains unstudied mainly due to its rarity and ethical challenges towards experimentation. Even though it's such an extraordinary phenomenon, it’s become quite a subject of mythos appearing in fantasy literature like ‘A Song of Ice & Fire’ series, religious texts, and ancient sculptures throughout history.

Source: 'Two heads are better than one? Anomalies of twinning' - EmbryoProject.org, Engel M. 1963. A two-headed bony fish; With a review of multiple-headed vertebrates. Journal of the Linnean Society of London, Zoology