Guest Post: The Descent of the Testes


I did not plan to write about testicles this week. And I do not recommend plugging the phrase “elephant testicles” into Google’s image search engine. But I had a nagging question about the fierce little mammal sketched above, and one literature search led to another. Before I knew it I was  — forgive me gentle readers — in balls-deep.

Backing up a bit: I went to visit some friends in South Africa this spring, and we spent about a week driving a popular stretch of coastline along the Indian Ocean. At nearly every rest stop we saw fat, marmot-like mammals called hyraxes — commonly known as dassies — sunning on the beach.  Dozens of dassies splayed on the rocks, just out of reach of the ocean spray.  Others nibbled grass or rummaged through trash cans. They weren’t aggressive, but had what my friend Lydia deemed Grumpy Old Man Face. If we got too close, they bared their tiny teeth.

Or tusks, rather.  The white protuberances that emerged from beneath the dassies’ whiskers were not fangs, but incipient tusks, like the ones elephants have. As it happens, dassies are the closest living relatives of elephants, aside from dugongs and manatees.  I tried to wrap my head around this strange fact by staring at diagrams of evolutionary trees on my phone in the back of the car, but it didn’t work — I just got carsick.  Later, when we actually touched elephants in a center that rehabilitates them, I looked in vain for any physical signs, besides those tiny tusks, that might have inspired scientists to connect dassies and the giant, rough-skinned, flap-eared beasts. My vacation-brain let it drop. When I got home, though, the question still bothered me.

Which brings me to testicles. It turns out that one sign of the kinship between elephants and dassies is something that you cannot see —internal testes. Most mammals have evolved testicles that dangle outside the body, for reasons that are still controversial. Some say external testes keep sperm cool. Others say they allow for movements such as galloping, which would rupture or damage them, though surely they are vulnerable outside, too. Others claim that, like fancy feathers, external testicles are made for display.

Male hyraxes, elephants and sea cows all store their testes inside the abdominal wall,  which some scientists interpret as a sign of shared aquatic origins, likely in the ancient Tethys Sea. This warm, shallow ocean — of which the Mediterranean is a small remnant — is thought to have been a cradle for the explosion of mammalian diversity that began 66 million years ago when dinosaurs went extinct. Why a dangling scrotal sac would be a disadvantage for aquatic mammals is not entirely clear to me, but some scientists speculate that it would cause unhelpful drag.

I failed to observe the missing testicles when I was comparing elephants and dassies, an easy mistake for the untrained eye.  Were there other obvious, shared physical traits I failed to notice, aside from the dassies’ frankly unconvincing  tusks? What could evolutionary biologists see that I didn’t?

Not a whole lot,  I learned by talking to an evolutionary biologist this week.  It took scientists until the 1990s to use genetic data to place hyraxes securely within the Paenungulate lineage, which includes elephants and seacows and belongs to the greater mammalian subgroup Afrotheria. The same line of research established a new order for other ancient African mammals, including elephant shrews, aardvarks, golden moles, and tenrecs — all of which I hope, someday, to see.


Emily Underwood is a freelance science journalist and correspondent for Science, based in Coloma, California.

Hyrax sketch by the author.

Redux: Coming of Age in a Trash Forest

My friend Taya and I were out at her parents’ country place, about twelve acres in the western foothills of the Cascades. I was maybe eight, visiting for the first time. Taya was taking me on a tour. We were struggling along, as short-legged people do through dense, early successional Northwest forest. She stopped and took hold of a small sapling. “This,” she said, “is the difference between our land and a park.” And then, shockingly, she stepped on the sapling until it was bowed in two and then snapped it with her boot, killing it dead. Or maybe she ripped it out of the ground with her two hands—she was a very strong girl, I remember. I don’t remember the details of the act. But I do remember that she killed a tree and also the sensation of my mind being blown right out my ears. (Taya’s childhood arbor-cide didn’t presage sociopathy or anything close to it. She’s now a veterinarian.)

I was a city kid, so well schooled in the “leave no trace” ethos of wilderness preservation by school and camp that the idea of killing a tree…it wasn’t that it was wrong. It was that I had never even considered the possibility. Nature was, to me, inviolate, unchanging, ancient and pure. Pristine. It was better than God—less judgmental, more fun to play in, but just as serious and Big. Continue reading

The Last Word

On Monday, Richard kicks off the week by giving history the finger. Galileo’s finger, that is: The middle finger of Galileo’s right hand is a satisfying sight. Not because the resemblance to an obscene gesture is unmistakable (though that’s pretty amusing). And not because such a gesture might suggest that in the end a scientist who suffered persecution for the sin of being correct had gotten the last word—well, two words (though that would be amusing, too).

It would be fun to walk with Helen, she’s always seeing interesting things. This time she’s on her way home from the library and she sees one of her favorite biological events. The 17-year-cicadas are in a genus called Magicicada. It does seem almost like magic to me, or maybe science fiction, the way our timelines line up for just a few weeks, as if we were on planets whose orbits cross only once every 17 years.

Erik tells himself he is ruled by logic. He has written about the benefits of vaccines and herd immunity. And then he takes his kid to the doctor: The sight of one little needle turns me into a raging antivaxxer.

Jessa writes about a researcher who studies plant roots in hopes of addressing the growing global demand for food: The stakes are higher than hunger. Plot the Food Price Index for all of the years of the 21st Century and you get a timeline of social and political instability. Just before major unrest, there’s reliably a spike in food prices.

And Friday, I reduxed a post about a weather phenomenon known as June Gloom (which is also know in the Pacific Northwest, very delightfully, as Juneuary). Hope the weather and your spirits are sunnier this weekend.


Photo: NASA Blueshift via Wikimedia Commons

Redux: June Gloom

It’s that time of year again: less than three weeks until the summer solstice, and I have pulled out my down vest, wool hat, scarf, and fuzzy boots. Yes, June Gloom is reduxing, as is this post, which originally appeared in 2012. But it’s not so bad. I love my fuzzy boots.


I used to think the weather was something adults talked about because they were boring. And now that’s me, commiserating with neighbors about the state of our sky, which gave us a glorious, bluebird May and then rolled out a thick cloud carpet on the first day of June. Continue reading

Tackling hunger from the root

In 2050, the global population is projected to stand at around 10 billion humans, and every one of them will need to eat. We already have more than 7 billion people on Earth, so perhaps another three seems like a step-wise challenge in global food security, but the scale of the problem turns out to be immense.

Cumulatively, from now to mid-century, we’re going to need to grow more food than we’ve grown in the history of agriculture – more food than was grown in the first 10,000-odd years since we’ve domesticated crops at scale. At the same time that we’re somehow managing to squeeze more food out of the dwindling arable land that urban sprawl hasn’t paved over, farmers will be coping with a perfect storm of threats.

Take fertilizer. The three big fertilizers are nitrogen, potassium and phosphorus, all of which are finite in their own way. Reserves of potash—salts that contain water-soluble potassium—are limited, and phosphate is more so. Meanwhile, the amount of oil it takes to convert nitrogen gas into ammonium nitrate fertilizer makes it an energy-expensive option. Freshwater will be at a premium—that is, when it’s not flooding—and to expand our farmland we’ll need to move into marginal areas, like salinated or acidic soils. Continue reading

In Defense of the Antivaxxer

I am a man of science. Okay, perhaps not of science, but certainly near it. I’m science adjacent. But regardless, I consider myself to be bound, in the end, by logic and facts.

As such, I like to think that I eschew my beliefs for what the facts tell me. As a very young man, I was very taken by the promise of herbal supplements. But as I came to understand the data (or lack thereof) behind them, I gave up on them. I used to worry about GMOs affecting my health until I dug into the actual science and realized that they are totally harmless (though not necessarily great for developing economies). I’m embarrassed to admit it, but in my overwhelmingly white college I thought that America was post-racial. But well-crafted arguments and data showed me I was wrong.

In every case, I abandoned what I thought for what I could prove. I try to keep an open mind and I tell myself I am ruled by logic. This was the mantra for my book on suggestibility and has become a guiding principle not just in my career but in my life.

It’s also utter self-delusion. The sight of one little needle turns me into a raging anti-vaxxer.

Continue reading

The Cicadas Come, on Little Hook Feet

Fifth-instar cicadas drag themselves up a tree trunk.


One evening this month I was coming back from the library. The pollen was at its worst, but I was sick of being indoors and thought I’d sit down on the grass in front of my building for a few minutes. I opened up one of my books, then felt guilty about choosing the world of the book over the world around me, closed it, and looked around.

There were buses and people and trees and birds to look at, but I was mesmerized by the grass. It’s not very nice grass, just whatever happens to grow there and to tolerate regular mowing. What amused me was watching it actively recovering from my having walked on it. Sproing! Sproing! One by one a blade would pop back up, marking my trail.

Then I noticed a different movement.

Continue reading

Redux: Giving History the Finger

At a thousand words, this picture would be way undervalued. But there it was, waiting to be taken (the picture, that is, not the object). So I took, during a visit to Florence, and I wrote, in 2014, and I redux, here, because some images you just can’t get out of your head.
fd3782c1-85d3-4f6c-a422-d63b25f5bacf.grid-4x2 The middle finger of Galileo’s right hand is a satisfying sight. Not because the resemblance to an obscene gesture is unmistakable (though that’s pretty amusing). And not because such a gesture might suggest that in the end a scientist who suffered persecution for the sin of being correct had gotten the last word—well, two words (though that would be amusing, too). And not even because the relic once belonged to the body of the real live Galileo Galilei (awesome). No, what pleased me most during my first personal encounter with the finger a few months ago was something more historically potent: its setting. Continue reading