Why squirrels masturbate

Since I mentioned in my last post that the amount of sperm produced by humans is literally astronomical, I've been thinking about which animals masturbate and why. For humans it seems to be a sexual outlet but is that the case for other mammals? How about non-mammals, do birds and bees masturbate? Well the motivating factor for male squirrels has been discovered, and it doesn't seem to be related to blue balls. Firstly, it appears that they are quite acrobatic:

“An oral masturbation was recorded when a male sat with head lowered and an erect penis in his mouth, being stimulated with both mouth (fellatio) and forepaws (masturbation), while the lower torso moved forward and backwards in thrusting motions, finally culminating in an apparent ejaculation, after which the male appeared to consume the ejaculate.”

Secondly, it seems to be motivated by cleanliness according to this paper:

"These results suggest that masturbation in this species was not a response to sperm competition nor a sexual outlet by subordinates that did not copulate. Instead masturbation could function as a form of genital grooming. Female Cape ground squirrels mate with up to 10 males in a 3-hr oestrus, and by masturbating after copulation males could reduce the chance of infection. Sexually transmitted infections (STIs) can profoundly affect fertility, and their consequences for mating strategies need to be examined more fully."

So who said masturbation was dirty?

Colbert to Congress: More Human-Fruit Hybrids!

sperm vs stars

Is there more sperm or more stars in the universe?

*World male population of "reproductive age" = 2.17 billion (Males aged 15-64)

*Average amount of sperm per ejaculate = 300 million

*Total sperm if everyone ejaculated= 6.5e17

*Total amount of stars in Milky Way = 1e11

AND

*total sperm produced in lifetime = 525 billion

*total male population = 3.3 billion

*total sperm for every male currently living during their lifetime = 1.73e21

*total stars in universe= 1e21

sources:
population (CIA)
sperm (wikipedia)
stars (nasa)

Fact or Fiction: Adam's Rib

And the LORD God caused a deep sleep to fall upon Adam, and he slept: and he took one of his ribs, and closed up the flesh instead thereof; And the rib, which the LORD God had taken from man, made he a woman, and brought her unto the man. Genesis 2:21-22 (King James Version)

I was asked recently whether it was true that women had a different number of ribs than men.

You may have heard this one before: Men have fewer ribs than women, either by a single rib or a pair. This notion follows from the biblical account of creation, whereby Eve was created from one of Adam's ribs and is used to support a literal interpretation of Genesis. But is it true?

The typical adult human skeleton has 206 bones and this number is the same for men and women. Of these, the ribs account for 24 (2 x 12). Seven of these pairs are connected to the sternum by cartilage, 3 are connected to the cartilage of the ribs above and 2 pairs, called floating ribs, are not attached to the sternum at all. These numbers are the same for men and women.

There are abnormalities that can alter the number of ribs. One such abnormality is a cervical rib which can cause thoracic outlet syndrome. A cervical rib is an extra rib arising from the seventh cervical vertebra, above the first rib ("normal" ribs are joined to the thoracic vertebrae). They are present in about 0.5% of the population. One large study of 10,000 radiographs looking at congenital rib abnormalities showed that women more often have cervical ribs, with a rate of about a 2.5 to 1 compared to males. This may be a reason for the propagation of the idea that females have more ribs than males, but in the typical, normal skeleton males and females have the same number of ribs.

How to make your data significant

Anyone who's been in science long enough to either get a grasp of statistics, or alternatively figure out empirically how to game it, knows that given enough parameters and data points you will inevitably reach statistical significance on something. So what's the difference between a p-value of 0.051 and 0.049? Well this guy sums it up with a good anecdote :

"About two years ago the Wall Street Journal (registration required) investigated the statistical practices of Boston Scientific, who had just introduced a new stent called the Taxsus Liberte.

Boston Scientific did the proper study to show the stent worked, but analyzed their data using an unfamiliar test, which gave them a p-value of 0.049, which is statistically significant.

The WSJ re-examined the data, but used different tests (they used the same model). Their tests gave p-values from 0.051 to about 0.054; which are, by custom, not statistically significant.

Real money is involved, because if “significance” isn’t reached, Boston Scientific can’t sell their stents. But what the WSJ is quibbling, because there is no real-life difference between 0.049 and 0.051. P-values do not answer the only question of interest: does the stent work?"

[...]

" Significance is vaguely meaningful only if both a model and the test used being are true and optimal. It gives no indication of the truth or falsity of any theory.

Statistical significance is easy to find in nearly any set of data. Remember that we can choose our model. If the first doesn’t give joy, pick another and it might. And we can keep going until one does."

Cancer Carnival #38 - Call for Submissions

The next edition of the Cancer Reseach Blog Carnival is coming up on Oct. 1 and will be hosted by Highlight HEALTH.

Highlight HEALTH will be hosting the next edition of the Cancer Research Blog Carnival, edition #38, on Friday, October 1st. As host, I invite you to send your submissions.

October is National Breast Cancer Awareness Month. Accordingly, the theme for next month’s edition of the Cancer Research Blog Carnival is Breast Cancer.

Submissions can be made through the blog carnival submission form or by email.

The Simpsons - Comments about PhDs and Grad Students. [HQ]

Cool video of the week

I'm a huge fan of Feynman, and always admired his curiosity about stuff outside of physics. In his biography (if you haven't read it, you're not a proper nerd) there is a passage about experiments with ants:

"I found out the trail wasn't directional. If I'd pick up an ant on a piece of paper, turn him around and around, and then put him back onto the trail, he wouldn't know that he was going the wrong way until he met another ant. (Later, in Brazil, I noticed some leaf-cutting ants and tried the same experiment on them. They could tell, within a few steps, whether they were going toward the food or away from it—presumably from the trail, which might be a series of smells in a pattern: A, B, space, A, B, space, and so on.)"

"I tried at one point to make the ants go around in a circle, but I didn’t have enough patience to set it up. I could see no reason, other than lack of patience, why it couldn’t be done."

Well Mr Feyman, not only can it be done, but it happens in nature...

Dance Dance Evolution

Scientists have finally figured out why I fare so poorly at the clubs: my dance moves. A paper published in Biology Letters and reported in the Globe and Mail describes research determining what dance moves are most attractive to women. Close to 40 women watched video clips of 19 different males (none of whom were professional dancers) whose images were motion captured and transformed into genderless, featureless avatars to put emphasis on movement and not on looks, as well as to save them the embarrassment when the dancing videos inevitably hit Youtube (follow these links for video samples from the supplementary materials of good and bad dancing). Males danced to a core drumbeat to eliminate music likeability as a confounder, and women judged the dancing. The researchers determined what movements were correlated with what women rated as "good" dancing. From the Globe and Mail article:

The study found that female perceptions of good dance quality were influenced most greatly by large and varied movements involving the neck and trunk.The speed of the right knee movements were also important in signalling dance quality.

A “good” dancer thus displays larger and more variable movements in relation to bending and twisting movements of their head/neck and torso, and faster bending and twisting movements of their right knee,” the researchers said in a report published in the Royal Society Journal Biology Letters.

So with that information in mind, it's time to design the perfect dance move - we just need to make sure we include some good head, torso and right knee movements. I'm imagining an exaggerated version of GOB's chicken dance:
(or maybe some moves from this pizza commercial)

The authors suggest that these movements signal "traits such as health, fitness, genetic quality and developmental history," likening them to courtship rituals in other animals. Dance being culturally influenced, I'd be curious to see if the elements of an attractive dance hold up across cultures. Likewise I'd be interested to see if their results are reflected by notable great dancers or if dance crazes of bygone eras are centred around these movements. In the meantime, I'll experiment with some of these motions, but I doubt they'll be winning hearts anytime soon.

2000 years old tetracyclin beer?

When tetracyclin was detected in large quantities in the bones of ancient Sudanese Nubians from 350-550 CE, many wondered if it was accidental. But evidence suggests that it was manufactured on purpose by growing streptomyces in beer. It seems to have been used therapeutically, including in children:

"“The bones of these ancient people were saturated with tetracycline, showing that they had been taking it for a long time,” he says. “I’m convinced that they had the science of fermentation under control and were purposely producing the drug.”

Even the tibia and skull belonging to a 4-year-old were full of tetracycline, suggesting that they were giving high doses to the child to try and cure him of illness, Nelson says."

Cancer Carnival #37

Friday of a long weekend? The only thing that could be better is a fresh edition of the Cancer Research Blog Carnival. The Carnival relies on posts and hosts, so be sure to submit your posts for next month, where the carnival will be hosted by Highlight HEALTH, who also start the proceedings this month.

In a recent post at HighlightHEALTH, Faith Martin discusses peer-reviewed research into the link between positive psychology and cancer survival.

Enter “Psychoneuroimmunology” – the field of study exploring the direct link between the nervous system and immune system, including the endocrine system, covering hormones. The brain controls these systems. Part of psychoneuroimmunology is the study of degree to which the action of these systems is impacted on by mental health and the way we think and process information around us. This is of particular interest when we exam the relationship between psychological experience, nervous/immune/endocrine systems and health conditions.

Faith goes on to describe how stress and psychology can impact physiology in ways that can affect tumor growth.

At Stem Cell Assays, Dr. Alexey Bersenev highlights high-throughput cancer stem cell-based screening assays to identify therapeutic compounds, in particular for neuroblastoma.

David at Health and Life, offers a brief summary on the history of cancer treatment and what future directions it is taking, with a particular mention of anti-angiogenic therapy. On the subject of anti-angiogenesis, Blane Tarr points us to a TED talk about anti-angiogenesis and dietary sources for certain anti-angiogenic compounds, such as ellagic acid from strawberries. Sticking with a dietary theme, Valentina Rey sends us a post about research into the effectiveness of produce in preventing lung cancer.

According to this new findings, a subject’s risk of developing lung cancer decreased when fruits and veggies were eaten, regardless of the amount—here, variety, not quantity, was important. Each different type of produce eaten reduced the risk of cancer by another 4%, up to a total decrease of 23%. This decrease occurred for all types of lung cancer, including squamous cell carcinoma, a type of cancer developed by smokers.

Here at the Bayblab, I provide an update, describing some sad news surrounding research into Devil Facial Tumor Disease. Other bloggers have also covered this story.

Finally, Orac has a post about the angiogenesis inhibitor Avastin, and the politics of drug approval.

Another lesson of the ongoing Avastin saga is about the very nature of science-based medicine itself. We have stated that we believe that medical care should be science-based. However, although medicine should be based on science, medicine itself can never be a pure science because so many non-science-based considerations impact on it. On the patient level, there is patient choice and how the doctor and patient weigh the patient's personal situation and personal considerations in choosing from among science-based therapies. At the national level, considerations of cost, politics, and values cannot be separated from medical policy considerations. Science can tell us that Avastin does not prolong overall survival in breast cancer patients and that it only very modestly prolongs progression-free survival. It can tell us that even that modest increase in PFS comes at a cost of complications that prevent improved PFS from translating to improved OS. What science can't tell us is whether that modest benefit is worth the cost. That's a value judgment that must be made both at the level of society as a whole and at the level of each patient and physician.

That's it for this month's Cancer Research Blog Carnival. For older editions, visit the Carnival Homepage. Don't forget, the CRBC has subscription options; you can follow by email or RSS feed. An aggregated feed of credible, rotating health and medicine blog carnivals is also available. For a broader collection of science-related blog carnivals, sign up for the Science, Medicine, Environment and Nature Blog Carnival Twitter Feed.

Next time you talk about a piss-warm beer...

Scicurious has a post up about - quite literally - piss beer. It describes a situation where yeast infections cause the fermentation of bodily fluids:

The second patient had “turbid” urine (that’s cloudy), and they suspected yeast, especially when they opened the bag of urine, and smelled BEER. Apparently this was so odd that the urine sample passed to every doctor in the room and down the hall. I can just picture a group of people in white coats, all gathered around with a cup of suspiciously yellow liquid, sniffing and saying “HEY GUYS! You gotta smell this!!!” Apparently the poor patient was so yeasty that her breath, and literally everything about her smelled like beer, and alcohol could actually be detected as a byproduct of the yeast.

(cue comparisons to your least favourite brew) I guess this is a bit of a different take on the human decanter.

Ghosts of Stem Cells Past

Are all induced pluripotent stem (iPS) cells created equal? How similar are they to ES cells? My latest post at the Stem Cell Network looks at two recent papers asking these questions.

RIP Cedric

You may remember stories here and elsewhere about transmissible cancer among tasmanian devils. Devil facial tumour disease (DFTD), as it's called, isn't spread by a virus but rather by allografts of tumour cells of Schwann cell origin that spread from animal to animal by biting. This had raised some interesting questions about the immunology of these tumours. How do they avoid immune rejection? Is it possible to create a preventative vaccine?

One key thought to hold the answer to DFTD that has wreaked havoc on the tasmanian devil community is Cedric, a devil that was thought to be immune to the cancer. But alas, Cedric was recently euthanized after two facial tumours that had been surgically removed had been shown to have spread to the animal's lungs:

In 2007, Menzies researchers injected Cedric and his half brother Clinky with facial cancer cells. Clinky developed the disease, but Cedric showed an immune response and grew no tumors — giving researchers hope that he could help them create a vaccine.

But in late 2008, Cedric developed two small facial tumors after being injected with a different strain of the cancer, which causes grotesque facial growths that eventually grow so large, it becomes impossible for the devils to eat. Current estimates suggest the species could be extinct within 25 years due to the prolific spread of the cancer.

Researchers removed the tumors, and Cedric appeared to be rallying. But X-rays taken two weeks ago showed the cancer had spread to the 5-year-old's lungs, Kreiss said. Tests confirmed the lung tumors were a result of facial tumor disease.

This is a blow to the scientists trying to understand and curtail the spread of DFTD, but hopefully data from Cedric will push forward new strategies to help the devil population.