The word baculum means "stick" or "staff" in
Latin and originates from
Greek: βάκλον, baklon "stick".[10]
Function
The baculum is used for copulation and varies in size and shape by
species. Its evolution may be influenced by
sexual selection, and its characteristics are sometimes used to differentiate between similar species.[11] A bone in the penis allows a male to mate for a long time with a female,[12][13] which can be a distinct advantage in some
mating strategies.[14][15] The length of the baculum may be related to the duration of
copulation in some species.[16][17] In carnivorans[18] and primates, the length of the baculum appears to be influenced by
postcopulatory sexual selection.[19] In some
bat species, the baculum can also protect the
urethra from compression.[20]
Presence in mammals
Mammals having a penile bone include various
eutherians:
Evidence suggests that the baculum was independently evolved 9 times and lost in 10 separate lineages.[25] The baculum is an exclusive characteristic of placentals and closely related eutherians, being absent in other mammal clades, and it has been speculated to be derived from the
epipubic bones more widely spread across mammals, but notoriously absent in placentals.[34]
Among the primates,
marmosets,[clarification needed] weighing around 500 grams (18 oz), have a baculum measuring around 2 millimetres (0.079 in), while the tiny 63 g (2.2 oz)
galago has one around 13 millimetres (0.51 in) 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.[15]
In some mammalian species, such as badgers[36][37] and raccoons (Procyon lotor), the baculum can be used to determine relative age. If a raccoon's baculum tip is made up of uncalcified cartilage, has a porous base, is less than 1.2 g (0.042 oz) in mass, and measures less than 90 mm (3.5 in) long, then the baculum belongs to a juvenile.[27]
Absence in humans
Unlike most primates, humans lack an os penis,[38][39] but the bone is present, although much reduced, among other
great apes. In many ape species, it is a relatively insignificant 10–20 mm (0.39–0.79 in) structure. Cases of
human penis ossification following trauma have been reported,[40] and one case was reported of a congenital os penis surgically removed from a 5-year-old boy, who also had other developmental abnormalities, including a
cleft scrotum.[41]Clellan S. Ford and
Frank A. Beach in Patterns of Sexual Behavior (1951), 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."[4] In humans, the rigidity of the
erection is provided entirely through blood pressure in the
corpora cavernosa. An "artificial baculum" or
penile implant is sometimes used to treat erectile dysfunction in humans.[42]
In The Selfish Gene,
Richard Dawkins[43] proposed honest advertising as the evolutionary explanation for the loss of the baculum. The hypothesis states that if erection failure is a sensitive early warning of ill health (physical or mental), females could have gauged the health of a potential mate based on his ability to achieve erection without the support of a baculum.
The tactile stimulation hypothesis proposes that the loss of the baculum in humans is linked to the female choice for tactile stimulation: a boneless penis would be more flexible, facilitating a larger range of copulatory positions and whole body movement, giving females greater general physical stimulation.[44]
The mating system shift hypothesis proposes that the shift towards monogamy as the dominant reproductive strategy may have reduced the intensity of copulatory and post-copulatory sexual selection, and made the baculum obsolete.[45][46]
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"[15][better source needed] 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 (unless the cervical mucus is examined),[47] so frequent matings would be necessary to ensure paternity.[15][48][49]
Strengths and weaknesses of these hypotheses were revised in a 2021 study, which also proposed an alternative hypothesis: that conspecific aggression, in combination with the development of self-awareness, may have played a role in the loss. If the presence of a baculum exacerbated the prevalence and severity of penile injuries resulting from blunt trauma to a flaccid penis, increasing ability to foresee the consequences of their actions would also enable hominins to realise that these injuries are a useful tool in male-male competition. This behavioural innovation, planned conspecific aggression with the goal of temporary exclusion of competitors from the breeding pool, would create an environment in which a genetic mutation for a penis without a baculum (or with an unossified baculum) would strongly increase the fitness of the mutant phenotype. Along with the hominin propensity for social learning and cultural transmission, this hypothetical scenario may explain why this phenotype became fixed in all human populations.[50]
An alternative view is that its loss in humans is an example of
neoteny during human evolution; late-stage fetal chimpanzees lack a baculum.[51]
Cultural significance
It has been argued that the "rib" (
Hebrewצֵלׇעṣēlāʿ, also translated "flank" or "side") in the 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.[52]
In
Hoodoo, the folk magic of the
American South, the raccoon baculum is sometimes worn as an amulet for love or luck.[53]
Oosik
Oosik (
Iñupiaq: usuk or uzuk) is a term used in
Alaska Native cultures to describe the bacula of
walruses,
seals,
sea lions and
polar bears. Sometimes as long as 60 cm (24 in), 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 sold as tourist souvenirs. In 2007, a 4.5 ft-long (1.4 m) fossilized penis bone from an extinct species of walrus, believed by the seller to be the largest in existence, was sold for $8,000.[54]
^Liddell, Henry George; Scott, Robert.
"βάκλον". An Intermediate Greek-English Lexicon. Tufts University.
Archived from the original on 5 February 2017. Retrieved 9 April 2017.
^
abcd"Godinotia". Walking With Beasts. ABC – BBC. 2002. pp. Question: How do we know how Godinotia (the primate in program 1) mated?. Archived from
the original on 29 April 2014. Retrieved 7 July 2015.
^Dixson, A. F. (1987). "Observations on the evolution of the genitalia and copulatory behaviour in male primates". Journal of Zoology. 213 (3): 423–443.
doi:
10.1111/j.1469-7998.1987.tb03718.x.
^Harvey, Suzanne.
"How Did Man Lose His Penis Bone?". University College London, Researchers in Museums blog, 26 November 2012.
Archived from the original on 25 October 2014. Retrieved 20 November 2014.
^Dawkins R (2006) The Selfish Gene. Oxford University Press, Oxford, UK.
^Cormier LA, Jones SR (2015) The Domesticated Penis: How Womanhood Has Shaped Manhood. University of Alabama Press, Tuscaloosa, USA.
^Brennan PLR (2016) The evolution of genitalia. In: Shackelford TK, Weekes-Shackelford VA (eds) Encyclopedia of Evolutionary Psychological Science, 1–4. Springer International Publishing, Cham, Switzerland
^Jakovlić, Ivan (2021) “The Missing Human Baculum: A Victim of Conspecific Aggression and Budding Self-Awareness?” Mammal Review.
https://doi.org/10.1111/mam.12237
^Bednarik, R. G. (2011). The Human Condition.
doi:
10.1007/978-1-4419-9353-3.
ISBN978-1-4419-9352-6. (page 134), cited by:
Achrati, Ahmed (November 2014). "Neoteny, female hominin and cognitive evolution". Rock Art Research. 31 (1): 232–238.
"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'"
^Joanne O'Sullivan (1 March 2010).
Book of Superstitious Stuff: Weird Happenings, Wacky Rites, Frightening Fears, Mysterious Myths & Other Bizarre Beliefs. Charlesbridge Publishing. p. 87.
ISBN978-1-60734-367-7.
Archived from the original on 29 December 2015. Retrieved 27 October 2015. 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 were photographed wearing them.
New Orleans gamblers are said to use the bones (also called coon dogs and Texas toothpicks) for luck.
Gilbert SF, Zevit Z (July 2001). "Congenital human baculum deficiency: the generative bone of Genesis 2:21–23". Am. J. Med. Genet. 101 (3): 284–5.
doi:
10.1002/ajmg.1387.
PMID11424148.
Clellan S., Frank A. Beach (1951). Patterns of Sexual Behavior. New York: Harper, and Paul B. Hoeber, Inc. Medical Books.
ISBN978-0-313-22355-6.
External links
Look up baculum in Wiktionary, the free dictionary.
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