Baculum

From Infogalactic: the planetary knowledge core
Jump to: navigation, search
Baculum of a dog's penis; the arrow shows the urethral sulcus.
Fossil baculum of a bear from the Miocene.

The baculum (also penis bone, penile bone or os penis) is a bone found in the penis of many placental mammals. It is absent in the human penis, but present in the penises of other primates, such as the gorilla and chimpanzee.[1] The bone is located above the male urethra,[2] and it aids sexual reproduction by maintaining sufficient stiffness during sexual penetration. The homologue to the baculum in female mammals is known as the baubellum or os clitoridis– a bone in the clitoris.[3][4][5]

Etymology

The phallic meaning of the term is unique to English; however, similar words exist in other languages with the same meaning, such as the Slovenian word bakulum. The word baculum originally meant "stick" or "staff" in Latin (c.f. Argumentum ad baculum).

Purpose

The baculum is used for copulation and varies in size and shape by species. Its characteristics are sometimes used to differentiate between similar species. A bone in the penis allows a male to mate for a long time with a female,[6] which can be a distinct advantage[clarification needed] in some mating strategies.[7]

Presence in mammals

A raccoon baculum.

Mammals having a penile bone (in males) and a clitoral bone (in females) include various eutherians:

It is absent in humans, ungulates (hoofed mammals),[15] elephants, monotremes (platypus, echidna),[citation needed] marsupials,[16] lagomorphs,[citation needed] hyenas,[17] sirenians,[2] and cetaceans (whales, dolphins, and porpoises),[2] among others.

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. The baculum is an exclusive characteristic of placentals and closely related eutherians, being absent in other mammal clades, and it has been speculated that it is derived from the epipubic bones more widely spread across mammals, but notoriously absent in placentals.[16]

Among the primates the marmoset, weighing around 500 g, has a baculum measuring around 2 mm, while the tiny 63 g galago has one around 13 mm long. The great apes, despite their size, tend to have very small penis bones, and humans are the only ones to have lost them altogether.[7]

In some mammalian species, such as the raccoon (Procyon lotor), the baculum can be used to determine relative age. If the baculum tip is made up of uncalcified cartilage, has a porous base, masses less than 1.2 g, and measures less than 90 mm long, then the baculum belongs to a juvenile male.[13]

Absence in humans

Unlike other primates, humans lack an os penis or os clitoris; however, this bone is present but is much reduced among the great apes: in many ape species it is a relatively insignificant 10–20 mm structure. There are reported cases of human penis ossification following trauma,[18] 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.[19] Clellan S. Ford and Frank A. Beach in Patterns of Sexual Behavior (1953), p. 30 say "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."[1] In humans, the rigidity of the erection is provided entirely through blood pressure in the corpora cavernosa.

It has been speculated that the loss of the bone in humans, when it is present in our nearest related species the chimpanzee, is because humans "evolved a mating system in which the male tended to accompany a particular female all the time to try to ensure paternity of her children"[7] which allows for frequent matings of short duration. Observation suggests that primates with a baculum only infrequently encounter females, but engage in longer periods of copulation that the baculum makes possible, thereby maximizing their chances of fathering the female's offspring. Human females exhibit concealed ovulation also known as 'hidden estrus', meaning it is almost impossible to tell when the female is fertile, so frequent matings would be necessary to ensure paternity.[7]

The evolutionary biologist[20] Richard Dawkins speculated in 1989 that the loss of the bone in humans, when it is present in our nearest related species the chimpanzee, is a result of sexual selection by females looking for honest signals 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.[21]

A third view is that its loss in humans was a side-effect of neoteny during human evolution; it is noted that late-stage fetal chimpanzees lack a baculum.[22]

Cultural significance

The existence of the baculum is unlikely to escape the notice of pastoralist and hunter-gatherer cultures.

It has been argued that the "rib" in the biblical story of Adam and Eve is actually a mistranslation of a Biblical Hebrew euphemism for baculum, and that its removal from Adam in the Book of Genesis is a creation story to explain this absence (as well as the presence of the perineal raphe– as a resultant 'scar') in humans.[23]

The raccoon baculum is sometimes worn as a charm for love or luck.[24]

Oosik

Oosik is a term used in Native Alaska cultures to describe the baculum of walruses, seals, sea lions, and polar bears. Sometimes as long as 60 cm (2 ft), fossilized bacula are often polished and used as a handle for knives and other tools. The oosik is a polished and sometimes carved baculum of these large northern carnivores.

Oosiks are also frequently sold as souvenirs to tourists by Alaska Natives. In 2007 a 4.5-foot (1.4 m) long fossilized penis bone from an extinct species of walrus, believed by the seller to be the largest in existence, was sold for $8,000.[25]

Walrus baculum, approximately 22 inches (59 centimetres) long.

See also

References

Notes

  1. 1.0 1.1 Patterns of Sexual Behavior Clellan S. Ford and Frank A. Beach, published by Harper & Row, New York in 1951. ISBN 0-313-22355-6
  2. 2.0 2.1 2.2 2.3 Lua error in package.lua at line 80: module 'strict' not found.
  3. Lua error in package.lua at line 80: module 'strict' not found.
  4. Lua error in package.lua at line 80: module 'strict' not found.
  5. Lua error in package.lua at line 80: module 'strict' not found.
  6. Dixson, A. F. "Baculum length and copulatory behaviour in carnivores and pinnipeds (Grand Order Ferae)." Journal of Zoology 235.1 (1995): 67-76.
  7. 7.0 7.1 7.2 7.3 Lua error in package.lua at line 80: module 'strict' not found.
  8. Lua error in package.lua at line 80: module 'strict' not found.
  9. Lua error in package.lua at line 80: module 'strict' not found.
  10. 10.0 10.1 Lua error in package.lua at line 80: module 'strict' not found.
  11. Lua error in package.lua at line 80: module 'strict' not found.
  12. Lua error in package.lua at line 80: module 'strict' not found.
  13. 13.0 13.1 Lua error in package.lua at line 80: module 'strict' not found.
  14. Baryshnikov, Gennady F., Olaf RP Bininda-Emonds, and Alexei V. Abramov. "Morphological variability and evolution of the baculum (os penis) in Mustelidae (Carnivora)." Journal of Mammalogy 84.2 (2003): 673-690.
  15. Lua error in package.lua at line 80: module 'strict' not found.
  16. 16.0 16.1 Lua error in package.lua at line 80: module 'strict' not found.
  17. Lua error in package.lua at line 80: module 'strict' not found.
  18. Lua error in package.lua at line 80: module 'strict' not found.
  19. Lua error in package.lua at line 80: module 'strict' not found.
  20. Lua error in package.lua at line 80: module 'strict' not found., of page 228
  21. Lua error in package.lua at line 80: module 'strict' not found.
  22. Lua error in package.lua at line 80: module 'strict' not found. (page 134), cited by:
    Lua error in package.lua at line 80: module 'strict' not found.
    "In humans, neoteny is manifested in the resemblance of many physiological features of a human to a late-stage foetal chimpanzee. These foetal characteristics include hair on the head, a globular skull, ear shape, vertical plane face, absence of penal bone (baculum) in foetal male chimpanzees, the vagina pointing forward in foetal ape, the presence of hymen in neonate ape, and the structure of the foot. 'These and many other features', Bednarik says, 'define the anatomical relationship between ape and man as the latter's neoteny'"
  23. Lua error in package.lua at line 80: module 'strict' not found.
  24. Lua error in package.lua at line 80: module 'strict' not found.
    "In the hoodoo (folk magic) tradition of the American South, a raccoon penis bone (scientifically known as the baculum) is a lucky charm used to attract love. In some areas it's boiled to remove any trace of the animal, and then tied to a red ribbon and worn as a necklace. In other areas, the bones were traditionally given to girls and young women by suitors, and in still other places, the charms are worn by men. Earrings made from cast raccoon penis bones became a fad in 2004, and celebrities such as Sarah Jessica Parker and Vanessa Williams[disambiguation needed] were photographed wearing them. New Orleans gamblers are said to use the bones (also called coon dogs and Texas toothpicks) for luck."
  25. Lua error in package.lua at line 80: module 'strict' not found.

References

  • Lua error in package.lua at line 80: module 'strict' not found.
  • Lua error in package.lua at line 80: module 'strict' not found.

External links