Blogs / Discoblog

As you’ve probably heard, a man’s testicles hang down because sperm are hyper-sensitive to temperature and need to be a little cooler than the inside of the body. But isn’t there more to it than that?

Oh, definitely yes, says research psychologist Jesse Bering, writing for Scientific American. Bering goes on at great length in his analysis of testicular location. Sure, he argues, the temperature part makes sense. But why would natural selection, which so rewards passing on your genes, put a man’s means of passing on those genes in such a terribly exposed place on his body?

Bering’s lengthy account of gonad geography, and the studies trying to explain it, includes some real gems:

One of the more fanciful accounts–and one ultimately discarded by the authors–is that scrotal testicles evolved in the same spirit as peacock feathers. That is to say, given the enormous disadvantage of having your entire genetic potential contained in a thin satchel of unprotected, delicate flesh and swinging several millimeters away from the rest of your body, perhaps scrotal testicles evolved as a sort of ornamental display communicating the genetic quality of the male.

Oh, and this, on how a man’s cremasteric muscle works to keep his sperm at an optimal temperature by contracting and drawing the testicles up on a cold day and relaxing when it’s hot:

[That's] why it’s generally inadvisable for men to wear tight-fitting jeans or especially snug “tighty whities”–under these restrictive conditions the testicles are shoved up against the body and artificially warmed so that the cremasteric muscle cannot do its job properly. Another reason not to wear these things is that it’s no longer 1988.

In all seriousness, there’s nothing Discoblog values more than analysis of the silly… other than over-analysis of the silly.  If you haven’t had your fill of scrotal hypotheses,  check out the rest of Bering’s post.

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Image: iStockphoto

Some sharks have a nasty habit of taking bites out of each other, but in an aquarium in New Zealand one aggressive shark ended up doing its tank-mate a favor when it tore out a piece of the second shark’s belly. Visitors at Kelly Tarlton’s Underwater World watched in shock as four baby sharks popped out of the gaping wound. The visitors ran to notify the aquarium staff, who quickly removed the babies.

Via the New Zealand Herald:

[Aquarium staff member Fiona] Davies said the unusual delivery had probably saved the baby sharks’ lives.

Staff did not know the mother was pregnant and, had she given birth naturally, most likely at night, the babies would have been eaten by adult sharks and stingrays before staff could rescue them.

When the mom was removed from the communal tank to get her wound stitched up, vets found four more babies inside her. All are reportedly doing well, despite the spontaneous C-section.

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Image: flickr / snickclunk

“Really! I was born that way! I swear!” A new species of shark was discovered in California recently, called the Eastern Pacific black ghostshark. It’s part of a group known as big black chimeras, and members of the species have actually been laying around pickled in museums since the 1960s—but only recently have scientists realized that the black ghostsharks were in fact a separate species.

One possibility is that past scientists were too distracted by the sharks’, er, highly unusual feature that they lumped them in with the other chimeras.

Douglass Long, author of the study (PDF) detailing the new species, described the shark to National Geographic News:

Male chimeras…have retractable sexual appendages sprouting from their foreheads. These organs, which resemble a spiked club at the end of a stalk, may be used to stimulate a female or to pull her closer—though these are still assumptions, Long said.

So basically these guys have a mace swinging from their forehead that they use to club female sharks. Talk about a remarkable trick of animal mating.

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Image: MBARI

You might remember the story that broke in early August saying that the Centers for Disease Control had greatly underestimated the number of Americans who become infected with HIV each year. The CDC had said the total was about 40,000; after correcting a mistake in their method of counting, the new estimate was 56,300, a 40 percent increase.

In response to this alarming new number, condom company One made a special delivery to both John McCain’s and Barack Obama’s campaign headquarters: 56,300 condoms. One says the shipments are campaigns’ to do with as they wish, but the company encourages them to donate the condoms to community centers or non-profit organizations.

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It’s a tough life being stuck in the zoo, especially for those looking for love. Animals might have one or two members of the opposite sex to choose from, maybe more if they’re lucky. But in this Internet age, when a Capricorn from Seattle and a Libra from South Carolina can connect on via a Web dating service, why shouldn’t animals have their own site?

Zoos had shared information about their animals before, trying to match them up the best way possible, but now the Zoological Information Management Systems has taken the process into the 21st century. The approximately 150 participating aquariums and zoos can not only see the size and weight of the eligible critters, but also read about their temperament.

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Not too long from now, men will scurry out to the car on the first chilly morning of autumn, jump inside, and enjoy the warm embrace of heated leather seats. But that warm feeling might have an unpleasant side effect—lowering one’s sperm count.

German scientists studied 30 men (subscription required), measuring their scrotal temperature after they had sat in a car seat for 90 minutes. Those who sat in heated seats measured an average of about 99.1 degrees Fahrenheit, up from about 98 degrees for men in plain old unheated seats. The scrotum is located outside the body because sperm production requires a lower temperature, and even a slight raise like the one in this study could interfere with that, the researchers say.

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Science: It sure can make those family relationships confusing.

A 61-year-old Japanese woman has given birth in Japan, which is extraordinary enough given her age. But this was no normal birth—the baby was her own grandchild. The Nagano hospital says the woman served as a surrogate mother for her own daughter, who does not have a uterus.

News reports are saying that the baby was born last year, despite the fact that the hospital didn’t announce it until today. That delay could have a lot to do with the attitude toward in vitro fertilization and surrogate births in Japan. They’re legal, but most hospitals and clinics won’t do them because the Japan Society of Obstetrics and Gynecology has banned its members from using the procedure. However, the doctor who runs the Nagano clinic in this case was booted from that organization a decade ago for providing in vitro fertilization for unmarried couples.

The hospital has not even divulged the baby’s sex, but says the birth went off without a hitch. Now all they have to do is figure out whose mother belongs to whom.

Image: iStockphoto

Soon, any woman hoping for a smart, tall Swede to be her sperm donor might just have to leave the U.S. to make it happen.

Since 2005, the Food and Drug Administration has made it essentially impossible to import sperm donations from Europe into the United States, the Washington Post reports, because of fears over the pathogens that cause mad cow disease and its human equivalent, Creutzfeldt-Jakob disease. And now, the last of the European sperm we imported before the embargo will soon be gone.

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Some have argued that homosexuality is unnatural because the biological purpose of sex is for reproduction, and gay couples can’t conceive children in the “natural” way. But as it turns out, homosexuality might actually be related to increased fertility and reproduction, though not in a way you might expect.

A team of Italian researchers led by Andrea Camperio-Ciani had been working on solving the Darwinian paradox of homosexuality—that is, if being gay is hereditary, and gay people have fewer or no children, homosexuality should have vanished from the gene pool. In 2004, the team studied Italian families and found that the female relatives of gay men were more fertile than average women. After using a series of computer models to analyze that data, the scientists released a study this week saying that homosexuality in men is genetically connected to women who have high fertility. In their model, male homosexuality has to be governed by two genetic loci—particular fixed positions on a chromosome—and at least one locus and maybe both must be on the X chromosome, meaning it’s passed down from mother to child.

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We thumb through real estate listings and drive around neighborhoods to find the best place to live, but some birds have it easier—they just listen to songs.

Male black-throated blue warblers sing to their newborn chicks in the autumn, probably trying to teach the young ones to sing themselves. But biologist Matthew Betts from Oregon State University, along with two Canadian colleagues, studied the warblers in New Hampshire and found that the song of males who successfully reproduced is also a cue—when other males hear it, they assume that location must be a good place to nest, and so they’ll try to return there the next year. Not only that, the scientists say, but eavesdropping on the songs other warblers can override the birds’ other senses.

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