The Gist has been on a field trip in New York City this week, taking culinary detours into Italy, Korea, Lebanon, Ireland and the Sichuan province of China.
The Grand Sichuan International in Chinatown is a living-room-sized restaurant with an invisible kitchen, a dozen tables, and a soft-drink cooler wedged against one wall. Grand or not, it’s where I learned the meaning of ma la, the Chinese name for a soup made of dried chilies and Sichuan pepper. It arrived as a steaming tureen, set before us on a portable gas burner and filled with a bright-red bubbling liquid. Crispy dried chilies – perhaps 40 of them – bobbed in the waves like radioactive minnows, and we eventually fished them out to keep the soup from getting any hotter.
But the real draw were the small woody flecks of Sichuan pepper floating in the broth. At first, these gave the soup a random and alarming crunchiness. But moments later the taste developed into a citrusy buzzing and tingling over my mouth and tongue. As it went on, the feeling almost perfectly balanced the heat from the chilies, mellowing it and sweetening it in waves that sloshed across my mouth. That’s ma la: “numbing hot.”
The nearest equivalent is the tingling you get from eating orange or lemon zest (or perhaps, the weird taste/sense as your tongue comes back to life at the dentist’s). But for me, the sensation brought back precisely a visit to a south Georgia barrier island some 15 years ago. I had searched the back dunes for a tree in the genus Zanthoxylum. Sometimes called “toothache tree,” the leaves are supposed to make your mouth go numb. When I found it, it was a short, stout tree covered with immense thorns and sporting leathery dark-green leaves. At the time I was disappointed that my mouth didn’t go completely numb, but the sensation was identical to the lemony fizz of my Sichuan hot pot.
Back home, a little reading turned up why. Sichuan peppercorns (or huajiao) are the dried seed husks of a few Asian species of Zanthoxylum (one of many neat botanical holdovers from the days before the Atlantic Ocean stood between Eurasia and North America).
Fortunately for us, ma la and Sichuan pepper have not escaped the notice of chemists, and a 1999 paper in Brain Research suggests why the spice can make our tongues feel so many things at once. The lemony taste and tingling sensations come from a half-dozen volatile oils, the most peculiar being something called hydroxy-alpha-sanshool. When scientists tested this compound (on rats), they found it activated several different classes of neurons, including touch-sensitive, cool-sensitive, and cold-sensitive receptors.
Sichuan pepper is in the citrus family and is unrelated to white, black, or red peppers. Importing the spice to the U.S. only became legal in 2005 after fears eased about its potential for transporting a citrus disease. So, if I arm myself with some Zanthoxylum berries and the right cookbook, might I be able to recreate my hot pot – and make my taste buds do back flips again? After my nose stops running, I’m going to try.
(Image: the toothache tree of North America, Zanthoxylum clava-herculis; amyb/Flickr)
Check out this deft rap about life on other planets by Jonathan Chase, a.k.a. Oort Kuiper (yes, that Oort and that Kuiper). The delivery is subdued and literate, like Massive Attack-era Tricky, and the video incorporates clips from Cosmos, the classic PBS series narrated by Carl Sagan. Bonus points for cribbing footage from SETI and working in a cameo by Gregor Mendel.
The bar on science rap has been raised. Once a novelty act confined to late-night grad-school potlucks, where just finding something to rhyme with “plate tectonics” was a triumph; now you get spot-on lyrics backed by leaping basslines and 1950s samples.
Other recent triumphs of the genre include the cogent Large Hadron Rap (405,000 hits in less than a month) and the salt-soaked Cruise, Cruise Baby. Say what you want about the LHR’s backup dancers (I was under the impression that experimental physics required nanosecond-accurate timing) – but I learned more about the setup, mechanics, and ambition of the Large Hadron Collider from this rap than from everything I’ve read on the subject previously put together.
Behavioral ecology, the study of what animals do and how it affects their lives, can be delightfully arcane. One research team designed a robot stickleback in order to learn how many fish it takes to persuade a school to change direction. (Early results suggest the answer is two.)
Another team found that African honeybee workers surreptitiously raise their own eggs rather than those of their queen overlords, in effect staging a bloodless coup.
Mitchell Baker, of Queens College, New York, had some amazing insights into pesticide resistance studying the formidable Colorado potato beetle. “If you leave them alone,” he said, “they will eat a field down to brown sticks.”
A pesticide, like an antibiotic, is supposed to kill any pest that’s not resistant to it. But when survivors get together to breed, one thing they all have to bequeath to their young is pesticide resistance. “Potato beetles can evolve resistance to anything you can throw at them, usually within three generations,” Baker said.
Resistance can have a downside for the beetle, though. It comes with a grab bag of handicaps. Through novel experiments at agricultural fields, Baker discovered that pesticide-resistant beetles hatch later, move more slowly, have compromised immune systems, mate less successfully, raise fewer young, die off during the winter at greater rates, and get cannibalized by their nestmates more often than non-resistant beetles.
Apparently, the genes that make a beetle resistant have such debilitating side-effects that it takes the application of deadly pesticides just for them to survive the competition. Baker’s research could point to ways to postpone widespread resistance by taking advantage of those weaknesses.
It’s tempting to view the world as a collection of species perfectly adapted to living together. But what I find fascinating about evolution are the compromises that constantly play out on any species’ scrap heap of talents. For potato beetles, pesticides are pulling resistance to the top of the pile. But change what’s killing them-a different pesticide, perhaps, or maybe hotter summers-and resistance will fall to the wayside in favor of something equally vital for the moment.
Filed under “Hang on a sec”: a new scientific paper has called into question one of the most exciting paleontological finds of the 21st century. Soft tissue discovered deep inside a Tyrannosaurus rex legbone may be a recent “biofilm” (what you might call scunge if you found it on a dishrag), not remnants of the Toothy One after all. That’s the suggestion of a team led by Thomas Kaye, writing in the scientific journal PLOS One.
Avid Smithsoniacs and dino fans may remember bits and pieces of this story. In 2005, paleontologists Mary Schweitzer and Jack Horner were stuffing a T. rex femur inside a too-small helicopter on their way home. They cracked the bone in half to make it fit, and Schweitzer noticed a goopy residue on the 65-million-year-old insides of the bone (see the Smithsonian story). Then this April, Schweitzer and her colleagues isolated a protein called collagen from the sample, analyzed it, and found striking similarities to the collagen of modern birds.
Kaye’s contradictory opinion comes from using an electron microscope to peer at similar residues he found in different fossils. Studying fossils of 17 dinosaur and mammal species, Kaye and his team saw evidence of biofilms, or slime left behind by bacteria that grew on the bone long after the dinosaur’s death.
Where Schweitzer’s group described the remains of red blood cells, Kaye’s team thought they were seeing iron-rich structures routinely built by bacteria. (The iron content and the structures’ characteristic shape might have made them look like red blood cells in some analyses, Kaye suggested.) Kaye found these structures time and again in his samples – even in a fossilized shell, which never would have contained blood at all. Worst of all, carbon dating suggested the biofilm was as recent as 1960.
Of course, there’s still the matter of the collagen’s similarity to chickens and ostriches – a detail Schweitzer was quick to point out to reporters. And Kaye didn’t sample the T. rex in question, leaving open the chance that Schweitzer’s find was the genuine article.
Personally, I’m leaning toward believing in the extraordinary. At least until the collagen results are explained (I mean, can anyone tell me if bacteria even make collagen?) Either way, it’s fascinating to listen to the well-constructed arguments on both sides. That’s what science is all about.
It’s been a good week for people who look through microscopes at fossils. First off, Scientific American told us about some German scientists who discovered evidence of 400-million-year-old life trapped in seawater trapped inside volcanic rock.
Far more buzz circled around the second report: that we may be able to figure out what color dinosaurs and ancient birds were. This means that one day, paleontologist-artists may have to stop dreaming up rosy purples and outlandish greens to clothe their dinosaurs in (remember Mark Witton’s lovely pterosaurs a few posts ago?).
The evidence sat in front of them for years in the form of a powdery residue on some fossils. It was long thought to be the meaningless remains of carrion-eating bacteria, but Yale graduate student Jakob Vinther’s electron microscope revealed the powder looked exactly like the pigment-bearing sacs that occur on modern-day feathers. Nowadays, those sacs are full of melanin which give birds colors ranging from black to russet brown.
Though the work was done on fossil birds, the scientists report that similar residues from dinosaur scales and the hair of ancient mammals may reveal their colors as well. The researchers were also careful to point out that the residues didn’t contain any intact melanin (unlike the T. rex discovered in 2005 with actual protein still preserved inside a massive thigh). A hundred million years is a long time, after all.
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It’s been a good week for people who look through microscopes at fossils. First off, Scientific American told us about some German scientists who discovered evidence of 400-million-year-old 
