The spotted hyena puts you to shame

I Have been accused of writing more about genitals than about science on the bayblab. OK, fine, but I give the people what they want... So I'll unload everything at once so we can concentrate on the science again.

The spotted hyena has had a bad reputation in the past. They are associated with death, scavenging, uncleanliness, cowardice, gluttony, sexual deviance. Early naturalist thought the hyena was a hermaphrodite, or that it practiced homosexuality. This was an understandable misconception. Female spotted hyena are actually slightly bigger than the male, and they have an enlarged clitoris that forms a pseudo-penis. The females give birth, copulate and urinate through their protruding clitoris. Interestingly, this anatomical feature is not dependent on high male hormones as was once thought, since, if testosterone is removed from the womb, they develop normally. The evolutionary advantage of this apparatus is unclear, as it makes copulation and birth more difficult. However, it does enable the female to have complete control over her mating partner, allowing the matriarchal society to persist.

There is a similar human condition of pseudo-hermatophroditism that results in an enlarged "clitoris". It is the consequence of 5-alpha reductase deficiency (5-ARD). The deficiency prevents the conversion of testosterone into DHT which is necessary for the development of male external genitalia. In fact there is an important cluster of 5-ARD in Papua New Guinea, where locals recognize 3 sexes in the society. Sexuality in New Guinea, has always intrigued explorers. The natives wear a Koteka, or penis-gourd, which can be pointy, curly, painted, massive, small penis-shaped depending on the tribe of origin. While the size of the penis gourd does not reflect status in the tribe, it is often used for communication such as saluting or expressing emotions such as astonishment. The explorer Matthew Stirling notes "They indicate astonishment by clicking their gourd penis covers with their finger nails and needless to say our camp sounded like a Western Union telegraph office most of the day as almost everything we had was a wonder to them."

But Papua New-Guinea natives have nothing on the Australian natives when it comes to penis salutations. The men of the Walibri tribe of central Australia, shake each others penises when they greet, much like we shake hands in the west. You can find numerous accounts of this custom of the Walibri tribe on the web, along with other strange sexual facts also in this book...

Tetragametic chimerism

I have a riddle for you: "The patient, who we will call Jane, needed a kidney transplant, and so her family underwent blood tests to see if any of them would make a suitable donor. When the results
came back, Jane was hoping for good news. Instead she received a hammer blow. The letter told her outright that two of her three sons could not be hers."
Well if you've paid attention to the title of this post you probably already know the answer. Jane is a chimera. She is a mix of cells from two twin sisters, conceived from two pair of gametes, that somehow got mingled up into one person. There are 30 or so reported cases of true tetragametic chimerism in the literature, often because they lead to hermaphroditism when the chimera is of a male and a female twin. However many more lurk around us without knowing. It may be just a few cells in the blood, or a patch in one organ, and you would probably never know...except from when you get blood type or genotype discrepancies. Such a case actually popped up recently when Tyler Hamilton was charged with blood doping after competing in a cycling race. He had two blood types in his veins, but it wasn't because of blood transfusion, he is a chimera. And the prevalence is mind boggling: 20-30% of the pregnancies that start out as twins end up as a single baby, and nearly 70% of all people may be chimeras. Although not everyone agrees with these statistics, it may explain, weird auto-immune disorders. And perhaps some transsexual people really are a girl trapped in a man's body, literally. here.