Does size matter? Yes, I'm talking about what you think I'm talking about

I’m not sure what’s more amusing, that people are studying how penis size affects male attractiveness or that the authors of the study are all men. Brian Mautz and Michael Jennions of Australian National University, Bob Wong from Monash University and Richard Peters of La Trobe University addressed the question of whether sexual selection could have played a role in the evolution of male genitalia. See, this is a serious study.

The authors presented 105 heterosexual women with life-sized computer-generated images of naked men. While there are obviously men who could also weigh in on penis preference, those relationships are irrelevant from an evolutionary standpoint. Enough said about that. The images varied in three ways: height, body shape and flaccid penis size, each with seven possible dimensions; thus, there were a total of 343 different images (there are examples in the paper, which I’m not going to reproduce here). The women were each shown a random subset of 53 of the images and asked to rank them for ‘attractiveness as sexual partners’.

The most important trait of the three being tested was body shape. Specifically, women liked to see the right shoulder to hip ratio in their potential paramours. In fact, nearly 80% of the variation in attractiveness could be accounted for by this one characteristic. Height and penis size did add a bit to the equation, but only about 6% and 5% respectively. Not surprisingly, taller women considered height to be more important than shorter women did.

So, does size matter? If we go back in history to a time before clothing, women could have used penis size to evaluate mates. However, if they were anything like modern women, male genitalia was not their top priority in choosing a partner. Besides, in this study, the meager advantage was in favor of penises that were considerably larger than normal (sorry, guys). This suggests that women’s inclinations probably did not greatly influence the current range of male equipment. Glad we got that cleared up.

UPDATE 4/10/13: Greg Laden has some interesting points about why the whole premise of paleolithic women being able to evaluate and select mates based on penis size is flawed at his blog.


Mautz, B., Wong, B., Peters, R., & Jennions, M. (2013). Penis size interacts with body shape and height to influence male attractiveness Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1219361110.

How to pick from seven sexes

Meet Tetrahymena thermophila, a one-celled eukaryote with seven different sexes (aka mating types). A cell of one mating type can successfully mate with a cell from any of the other six mating types. And that’s not even the most interesting part of this tiny creature’s sex life. It turns out that the mating types are assigned stochastically. According to first author Marcella Cervantes of the University of California, Santa Barbara and her colleagues, each cell’s mating type is effectively determined by random chance rather than by genetic history.

Our story begins with the observation that T. thermophila have two nuclei rather than one. One nucleus contains the ‘somatic’ genome, which is responsible for the everyday running of the cell. The other, smaller nucleus contains the inactive ‘germline’ genome. We keep our germline genomes in our ovaries and testes. Within the germline genome are all seven pairs of sex determination genes, one for each of the possible mating types. The somatic genome contains only a single set of mating type genes, and it is this set that determines what that cell’s sex will be.

This means that while each T. thermophila cell contains all the genetic material necessary to become any mating type, six of those genes are only found in the quiescent germline genome. Only one set of mating type genes finds its way into the actively expressed somatic genome. Here’s how that happens.

When two T. thermophila mate, they exchange genetic material with each other (unlike with our unions, no third individual is created). Both cells subsequently destroy their own somatic genomes. They then use material from their germline genomes to construct new somatic genomes. But remember, the germline genome includes genes for all seven sexes. During the process of rebuilding the somatic genome, six of those mating types genes are excised so that only a single one remains. There is an equal probability that any one of the seven sets of mating type genes could be the last one standing.

This means that the sex of the cell after a conjugation event is in no way related to the sex of that same cell before that event. Meanwhile, the ‘reborn’ cell retains all the mating type genes within its own germline genome so that it can continue the tradition.

You might be wondering why an organism would need seven different sexes. Note that T. thermophila only mate under conditions of extreme duress. When you're in danger of starving to death, it’s best not to waste too much time looking for a suitable mate, especially when you’re only 40 or so microns long and can only travel so far. If you can successfully mate with six out of every seven potential partners you meet, so much the better.

Image top left: Tetrahymena thermophila 
Credit: Robinson, R. (2006). Ciliate Genome Sequence Reveals Unique Features of a Model Eukaryote PLoS Biology, 4 (9) DOI: 10.1371/journal.pbio.0040304

Article: Cervantes, M., Hamilton, E., Xiong, J., Lawson, M., Yuan, D., Hadjithomas, M., Miao, W., & Orias, E. (2013). Selecting One of Several Mating Types through Gene Segment Joining and Deletion in Tetrahymena thermophila PLoS Biology, 11 (3) DOI: 10.1371/journal.pbio.1001518.

Robots for off the beaten path

It's hard enough for humans to slog through soft sand, how well could a robot possibly handle that kind of terrain? Pretty well, if it's the prototype designed by Chen Li of UC Berkeley and Tingnan Zhang and Daniel Goldman of Georgia Tech. You can see one of their designs below:



You won't be surprised to learn that the scientists used lizards and insects for inspiration in building their robot. In particular, they were interested in how animals make multifunctional usage of their limbs to cope with different situations. To that end, they made their robots struggle through sand, glass spheres, and even poppy seeds.

The authors expect their research to pay off in building better robots for both exploring other planets and for search and rescue missions here on Earth. However, those are just two of the myriad uses for a robot that doesn't require solid ground for movement.

You can see Goldman explain the results below. Yet another use for 3D printing!




Li, C., Zhang, T., & Goldman, D. (2013). A Terradynamics of Legged Locomotion on Granular Media Science, 339 (6126), 1408-1412 DOI: 10.1126/science.1229163.

Waking up during surgery is a rare event

One of the worst nightmares for anyone contemplating surgery is of waking up during the operation. Unfortunately, this does happen, albeit extremely rarely. Anesthetists make every effort to ensure that people do not wake up when they’re not supposed to, and that includes collecting data on the events. To that end, anesthetists from the UK and Ireland have conducted a huge survey on accidental awareness during general anesthesia.

They found a few interesting things, many of them reassuring. Between the over 7000 anesthetists surveyed, there were only 153 cases of accidental awareness, or one in about 15,000 surgeries. This is considerably lower than the previous reports of one per thousand. This discrepancy could be because complaints about waking up in surgery were not passed on to the anesthetists, who typically do not interact with patients after surgery. More hopefully, the rates have really decreased significantly.

Of these accidental awakenings, nearly half were caught before the surgery actually started. There were only 46 cases of patients waking up on the operating table, or about one in 50,000. 

In the not at all surprising category: people who woke up during surgery experienced more pain and distress than people who woke up before or too soon after the surgery.

What can be done to cut down the incidents of accidental awareness during surgery even more? Two words: training and monitoring. Although two thirds of the UK medical centers in the survey provided depth of anesthesia monitors, less than 2% of anesthetists routinely use them. Only 4.5% of the centers have any kind of policy for preventing or managing awareness during surgery.

By the way, waking up during surgery was not considered the worst surgical complication for either patients or doctors. For patients, nausea and vomiting took first place. For anesthetists, it was death. I’m glad to see that the anesthetists have their priorities right.


Pandit, J., Cook, T., Jonker, W., O'Sullivan, E., & , . (2013). A national survey of anaesthetists (NAP5 Baseline) to estimate an annual incidence of accidental awareness during general anaesthesia in the UK Anaesthesia, 68 (4), 343-353 DOI: 10.1111/anae.12190.

Just for fun: Solar Roadways

I'm a huge proponent of solar power. We just got solar panels installed on our home, and so far, we love them. So you can imagine how excited I was to hear about the possibility of building solar roadways. The safety possibilities with LEDs and sensors are particularly intriguing.



You can read more about solar roads and about Wireless Advanced Vehicle Electrification (WAVE) at Co-Exist.

It's the second ever quasar triplet!

An international team of astronomers, led by Emanuele Farina of the University of Insubria in Como, has discovered a triplet of quasars. At this point, you might be thinking, ‘this would be a whole lot more exciting if I knew what a quasar was’. Or maybe that’s just me. In any case, writing this article gave me a great excuse to learn more about quasars.

To begin with, ‘quasar’ is actually short for ‘quasi-stellar radio source’. That is, it's a source of electromagnetic energy that’s emanating from a star-like point.  In fact, a quasar is no kind of star but a supermassive black hole surrounded by an accretion disk. For this reason, cosmologists now call them quasi-stellar objects (QSOs), so I’ll switch to that terminology. As material falls toward that black hole, massive collisions occur that form the accretion disc circling the black hole and emit energy.

Actually, that understates the case quite a lot. QSOs are among the brightest objects in the entire universe, each one putting out many times the energy of an entire galaxy. This is why we can see them at all, since they are also among the farthest objects, each at least three billion light years away. QSOs are found at the center of some young galaxies. In fact, we often only know about that galaxy’s existence because we see the QSO in its center. Galaxies in which a supermassive black hole is actively munching on the stars around it at a great enough rate to produce a QSO, are called ‘active galaxies’.

To make things even more interesting, all the energy from a QSO is usually projected along a single line rather than equally in all directions. You can see an artist’s rendition of this above.

So, at the center of a galaxy, you have a supermassive black hole (with a mass of about a billion of our suns) that’s generating enough energy to become an incredibly bright QSO. Under rare circumstances, possibly due to the collision of two such galaxies, you end up with a binary system of QSOs. Imagine how often three such galaxies combine. To give you an idea, this is only the second triplet group of QSOs ever found (the previous one was discovered over six years ago). Because of the placement of the three QSOs, the authors suggest that two of them (B and C) interacted with each other first before the third one (A) joined the grouping.

An infrared image of the triple quasar system QQQ J1519+0627, made using the 3.5-m aperture telescope of the Calar Alto Observatory. The three quasars are labelled A, B and C.

Credit: Emanuele Paolo Farina.

I think you can now see why this news is so exciting. Click the reaction boxes below to let me know if you agree.

You can learn more about QSOs here, here and here.

Farina, E., Montuori, C., Decarli, R., & Fumagalli, M. (2013). Caught in the act: discovery of a physical quasar triplet Monthly Notices of the Royal Astronomical Society DOI: 10.1093/mnras/stt209.

Giant robotic jellyfish to roam the seas

No, this isn’t an April Fool’s prank. Engineers at the Virginia Tech College of Engineering are really at work developing a robot that mimics the swimming ability of jellyfish. You can see an 80 kg prototype, dubbed Cyro, being tested by Virginia Tech students below.

Why emulate a jellyfish? Jellyfish expend remarkably little energy for propulsion. A robot using similar methods of locomotion would be able to travel great distances without recharging. Thus, they could be sent on long reconnaissance or environmental monitoring missions. For example, the robots could be used to map the ocean floor or monitor water quality. Of course, they are being funded by the US Naval Undersea Warfare Center, so that probably does not rule out military or surveillance usage. But don’t worry, the researchers, led by Shashank Priya, are years away from having a fully functional model.

By the way, here’s the creature that inspired the engineers: Cyanea capillata, or lion’s mane jellyfish. It's the largest known jellyfish, with a bell over two meters across and tentacles that can reach 37 meters. The name ‘Cryo’ is a combination of ‘Cyanea’ and ‘robot’.

 

Credit: Dan Hershman

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