- baculus (rare)
- English: baculum
The baculum (also penis bone, penile bone or os penis) is a bone found in the penis of most mammals. It is absent in humans, equids, marsupials, lagomorphs, and hyenas, amongst others. It is used for copulation and varies in size and shape by species. Its characteristics are sometimes used to differentiate between similar species.
The oosik of Native Alaskan cultures is a polished and sometimes carved baculum of various large northern carnivores such as walruses. The raccoon baculum is sometimes worn as a luck or fertility charm.
The word baculum originally meant "stick" or "staff" in Latin. The homologue to the baculum in female mammals is known as the baubellum or os clitoridis or os clitoris.
Clellan S. Ford and Frank A Beach, Patterns of Sexual Behavior, p. 30 says "Both gorillas and chimpanzees possess a penile bone. In the latter species the os penis is located in the lower part of the organ and measures approximately three-quarters of an inch in length."
In humans, which lack the baculum and baubellum, the rigidity of the erection is provided entirely through blood pressure in the corpus cavernosum.
Mammals having a penile bone (in males) and a clitoral bone (in females) include various eutherian Orders (not Marsupials or Monotremes):
- Order Primates (excluding humans)
- Order Rodentia (rodents), though not in the related order Lagomorpha (rabbits, hares etc)
- Order Insectivora (insectivores, including moles, shrews, and hedgehogs)
- Order Carnivora (including members of many well-known Families, such as Ursids (bears), Felids (cats), Canids (dogs), Pinnipeds (Walruses, Seals, Sea Lions), Procyonids (Raccoons etc), and others
- Order Chiroptera (bats)
Such a wide distribution among placental mammals suggests that the bone evolved early in the history of these mammals, and was subsequently lost in certain groups.
Raccoon penis boneA raccoon penis bone is the baculum of a raccoon. It is sometimes used as a charm for luck or fertility.
Author JT LeRoy's story Sarah features raccoon penis bones, as does William Gibson's novel, Count Zero.
Oosik is a term used in Alaska to describe the baculum (penile bone) of walruses, seals, sea lions, and polar bears. Sometimes as long as 60 cm (2 ft), it can be polished and used as a handle for knives and other tools. It is also frequently sold as a souvenir to tourists by Alaska Natives, the only people permitted to hunt the walrus today. In 2007 a 4.5 foot long fossilized penis bone from an extinct species of walrus, believed by the seller to be the largest in existence, sold for $8000.
Absence in humans
Humans, unlike other primates, lack an os penis / os clitoris. However, this bone is much reduced among the great apes: in many species it is a relatively insignificant 10-20 mm structure. There are reported cases of human penis ossification following trauma, and one reported case of a congenital os penis surgically removed from a 5 year old boy, who also had other developmental abnormalities, including a cleft scrotum.
The zoologist Richard Dawkins speculated in 2006, that the loss of the bone in humans, when it is present in our nearest related species the chimpanzee, is probably a result of sexual selection by females looking for signs of good health in prospective mates. The reliance of the human penis solely on hydraulic means to achieve a rigid state makes it particularly vulnerable to blood pressure variation. Poor erectile function betrays not only physical states such as diabetes and neurological disorders but mental states such as stress and depression.
- Gilbert, Scott F. and Ziony Zevit. 2001. Congenital human baculum deficiency: The generative bone of Genesis 2:21–23. American Journal of Medical Genetics 101(3): 284–285.
- Clellan S. And Frank A. Beach 1951 Patterns of Sexual Behavior Publisher: N.Y., Harper, and Paul B. Hoeber, Inc. Medical Books (ISBN 0313223556)
- Beresford WA, Burkart S. The penile bone and anterior process of the rat in scanning electron microscopy. J Anat. 1977 Dec;124(3):589–97.
- The San Diego Zoo's Conservation and research for endangered species projects. 'What is the significance of the baculum in animals?'
- Ode to an Oosik – poem and picture of an Oosik
baculum in German: Penisknochen
baculum in Spanish: Báculo (hueso peneano)
baculum in French: Baculum
baculum in Croatian: Penisna kost
baculum in Italian: Osso penico
baculum in Dutch: Penisbot
baculum in Japanese: 陰茎骨
baculum in Polish: Kość prącia
baculum in Russian: Бакулюм
baculum in Slovenian: Bakulum
baculum in Swedish: Penisben