June 19, 2013
For nearly two centuries, biologists have been struck by a mystery of geography and biodiversity peculiar to Europe. As Edward Forbes pointed out as far back as 1846, there are a number of life forms (including the Kerry slug, a particular species of strawberry tree and the Pyrenean glass snail) that are found in two specific distant places—Ireland and the Iberian Peninsula—but few areas in between.
Recently, Adele Grindon and Angus Davidson, a pair of scientists at the University of Nottingham in the UK, decided to come at the question with one of the tools of modern biology: DNA sequencing. By closely examining the genetic diversity of one of the species shared by these two locales, the grove snail, they thought they’d be able to trace the migratory history of the creatures and better understand their present-day distribution.
When they sequenced the mitochondrial DNA of hundreds of these snails scattered across Europe, the data pointed them towards an unexpected explanation for the snails’ unusual range. As they suggest in a paper published today in PLOS ONE, the snails likely hitched a boat ride from Spain to Ireland some 8,000 years ago along with migrating bands of Stone Age humans.
Grove snails as a whole are distributed all over Europe, but a specific variety of the snail, with a distinctive white-lipped shell, is found exclusively in Ireland and in the Pyrenees mountains that lie on the border between France and Spain. The researchers sampled a total of 423 snail specimens from 36 sites distributed across Europe, with an emphasis on gathering large numbers of the white-lipped variety.
When they sequenced genes from the mitochondrial DNA of each of these snails and used algorithms to analyze the genetic diversity between them, they found that the snails fell into one of 7 different evolutionary lineages. And as indicated by the snails’ outward appearance, a distinct lineage (the snails with the white-lipped shells) was indeed endemic to the two very specific and distant places in question:
Explaining this is tricky. Previously, some had speculated that the strange distributions of creatures such as the white-lipped grove snails could be explained by convergent evolution—in which two populations evolve the same trait by coincidence—but the underlying genetic similarities between the two groups rules that out. Alternately, some scientists had suggested that the white-lipped variety had simply spread over the whole continent, then been wiped out everywhere besides Ireland and the Pyrenees, but the researchers say their sampling and subsequent DNA analysis eliminate that possibility too.
“If the snails naturally colonized Ireland, you would expect to find some of the same genetic type in other areas of Europe, especially Britain. We just don’t find them,” Davidson, the lead author, said in a press statement.
Moreover, if they’d gradually spread across the continent, there would be some genetic variation within the white-lipped type, because evolution would introduce variety over the thousands of years it would have taken them to spread from the Pyrenees to Ireland. That variation doesn’t exist, at least in the genes sampled. This means that rather than the organism gradually expanding its range, large populations instead were somehow moved en mass to the other location within the space of a few dozen generations, ensuring a lack of genetic variety.
“There is a very clear pattern, which is difficult to explain except by involving humans,” Davidson said. Humans, after all, colonized Ireland roughly 9,000 years ago, and the oldest fossil evidence of grove snails in Ireland dates to roughly the same era. Additionally, there is archaeological evidence of early sea trade between the ancient peoples of Spain and Ireland via the Atlantic and even evidence that humans routinely ate these types of snails (pdf) before the advent of agriculture, as their burnt shells have been found in Stone Age trash heaps.
The simplest explanation, then? Boats. These snails may have inadvertently traveled on the floor of the small, coast-hugging skiffs these early humans used for travel, or they may have been intentionally carried to Ireland by the seafarers as a food source. “The highways of the past were rivers and the ocean–as the river that flanks the Pyrenees was an ancient trade route to the Atlantic, what we’re actually seeing might be the long lasting legacy of snails that hitched a ride…as humans travelled from the South of France to Ireland 8,000 years ago,” Davidson said.
All this analysis might help biologists solve the bigger mystery: why so many other species share this strange distribution pattern. More research could reveal that the Kerry slug, strawberry tree and others were carried from Iberia to Ireland by prehistoric humans too—and that, as a species, we were impacting the Earth’s biodiversity long before we could’ve possibly realized it.
June 18, 2013
Cyprus, the Mediterranean island nation just south of Turkey, took centuries to gain its independence. The Greeks, Assyrians, Egyptians, Persians, Romans, Ottomans, British and others all took their turns taking over the island, and each left their mark on the archeological record. But in a ruined chamber in a castle on the western corner of the island, it may be more apt to say the invaders left a smear.
In 1191, during the Third Crusade, King Richard I of England invaded Cyprus and ordered that a castle be built on the island’s western corner in order to defend the harbor there. Called Saranda Kolones, the castle’s name refers to its many monolithic columns. But in typical tumultuous Cyprus fashion, the medieval castle was only used for thirty years before it was destroyed by an earthquake. By then, King Richard had sold Cyprus to Guy de Lusignan, the King of Jerusalem. Lusignan and his successors had other plans for expanding the island. The wrecked port was abandoned and the castle never rebuilt.
As castles go, Saranda Kolones had a pretty poor run. But two University of Cambridge researchers recently realized that, precisely thanks to the castle’s short use, a priceless treasure had been left behind in the Saranda Kolones’ bowels. One of the centuries-old castle latrines (read: ancient toilet), they found, was still full of dried-up poo. That feces, they thought, could provide valuable insight into what kind of parasites plagued the former residents’ guts. And because only 30 years’ worth of waste clogged the ancient sewage system, those parasites could provide specific insight into what ailed medieval crusaders. The researchers rolled up their sleeves and collected samples from the dessicated cesspool.
To rehydrate the ancient night soil, the team placed one gram of their sample into a chemical liquid solution. They used micro sieves, or tiny strainers to separate parasite eggs from the digested remains of the crusaders’ meals. They created 20 slides, and peeked into their microscopes to see what creatures the soldiers may have left behind.
The samples revealed 118 “lemon-shaped” Trichuris trichiura eggs–a type of roundworm commonly called the whipworm–as well as 1,179 Ascaris lumbricoides, or giant roundworm, eggs. A control sample of non-toilet soil they tested did not contain any parasite eggs, confirming that the eggs did indeed come from the toilet, they report in the International Journal of Paleopathology.
The study of ancient parasites, whether through old bones that reveal leprosy-causing pathogens or dried up leaves that elucidate the cause of the Irish potato famine, is a thriving field. In this case, the long-dead parasite eggs were pooped out by the crusaders using the toilet years ago. These species reproduce within human bodies, and go on to infect new hosts through egg-contaminated soil or food delivered courtesy of the host.
Heavy infection with either of these worms was no picnic. The authors write, first of giant roundworms:
The mature female then starts to lay about 200,000 eggs per day that can be fertile or unfertile if no male worms are present. Although a mild infection with roundworms is mostly asymptomatic, heavy burdens with Ascaris can cause intestinal blockage and abdominal pain in adults. Because children are less able to tolerate parasites that compete with them for nutrients in their diet, heavy infection with roundworms can cause nutritional impairment, vitamin deficiencies, anaemia and growth retardation.
And of whipworms:
When the females reach maturity they can release 2000–10,000 eggs per day. As with roundworm a heavy worm burden may contribute to malnutrition, stunted growth in childhood and sometimes mechanical damage of the intestinal mucosa, diarrhoea and prolapsed rectum.
The presence of these worms, the authors write, attests to the poor hygienic conditions the castle residents likely practiced and put up with. “Poor hygiene with dirty hands, contamination of the food and water supplies with faecal material, inadequate disposal of the faecal material, and consumption of unwashed vegetables fertilized with human faeces are some of the means through which roundworms and whipworms are spread.”
The worms also could have jeopardized the health of their hosts, especially during years of famine when both parasite and human competed for scarce nutrients from meals few and far between. Previous studies found that between 15 to 20 percent of nobles and the clergy died from malnutrition and infectious disease during the crusades. Although death records for poor soldiers are not available, the authors think it’s safe to assume that malnutrition probably hit the lower-ranking crusaders even harder.
“It is quite likely that a heavy load of intestinal parasites in soldiers on crusade expeditions and in castles undergoing long sieges would have predisposed to death from malnutrition,” they write. “This clearly has implications for our understanding of health and disease on mediaeval military expeditions such as the crusades.”
Before contemporary readers breathe a sign of relief that these parasites infested the guts of people living more than 800 years ago, it’s important to note that the giant roundworm infests an estimated one-sixth of all humans living today. As the authors write, “In modern times A. lumbricoides and T. trichiura are two of the most common and widespread intestinal parasites.” Other parasites continue to plague human populations worldwide, especially in developing countries. Who knows what the archaeologists of the future will find in the scum of your latrine?
June 12, 2013
Visit a sunny pond in a meadow, park or zoo and you’ll likely see turtles basking on logs and small lizards hanging out on warm rocks. If you’re in the south, you may even spot an alligator lazing on a bright patch of shore.
Ectotherms (better known as cold-blooded animals) such as these reptiles have to shuttle back and forth between shade and sun in order to manually regulate their body temperature. Insects, fish, amphibians and reptiles all do it. Now, new research suggests that these animals begin their temperature-regulating tasks much earlier than previously thought–while they are embryos encased in their eggs.
Previously, researchers thought of developing embryos as cut off from the outside world. But back in 2011, researchers found that Chinese soft-shelled turtle embryos could move between warmer or cooler patches in their eggs, though they lacked any feet at such an early stage of development. Some of the same Chinese and Australian researchers who published that original finding decided to investigate further to see just how deliberate these movements are.
“Do reptile embryos move away from dangerously high temperatures as well as towards warm temperatures?” the team, writing in the journal Biology Letters, wondered. “And is such embryonic movement due to active thermoregulation, or (more simply) to passive embryonic repositioning caused by local heat-induced changes in viscosity of fluids within the egg?”
In other words, are unborn reptiles purposefully moving from one spot to another within their eggs, much like an adult animal does? The team decided to investigate these questions by experimenting on turtle embryos. They incubated 125 eggs from Chinese three-keeled pond turtles. They randomly assigned each of the eggs to one of five temperature groups: constant temperature, hot on top/cool on the bottom, or at a range of heats directed towards one end of the egg.
When they began the experiment, most embryos sat in the middle of their eggs. A week after exposing them to the different temperature groups, the team again measured the baby turtles’ positioning within the eggs. At the 10-day mark, the researchers again measured the turtles’ positions, and then injected half of the eggs with a poison that euthanized those developing embryos. Finally, after another week, they took one last measurement of the developing turtles and euthanized turtles.
The turtles within the eggs held at constant temperature or those that were in the “warm on the top/cool on the bottom” group tended not to shift around in their eggs, the researchers found. Those belonging to the groups that experienced warm temperatures only on one end of their egg, however, did move around. They gravitated towards warm conditions (84-86°F), but if things heated up too extremely (91°F), they edged towards the cooler side of their egg. Crucially, the embryos that the researchers euthanized stopped moving after receiving the dose of poison. This shows that the embryos themselves, not some passive physical process, are doing the shifting.
The turtle embryos, the researchers note, behave much like adult reptiles do when thermoregulating their bodies. They warm up and cool down by moving toward or away from heat sources. For species like turtles, temperature during development plays an important part of determining the embryo’s sex. Turtle nests, which are buried in the sand, often experience a range of different temperatures, so embryos could be playing a role in determining their own gender, edging towards the cooler side of the egg if they feel like becoming a male, or the warmer side if they’re more female-inclined, the authors write.
June 11, 2013
Science is generally considered a rather serious business, full of big questions, dense calculations and incomprehensible jargon.
Then there is the Annals of Improbable Research, a venerable journal that has published data on the effects of peanut butter on the rotation of the Earth and how access to television can be an effective method of birth control. The publication’s stated goal is to publish “research that makes people laugh and then think.” Its articles—which are mostly satire, but with some occasional real research into offbeat issues—probably accomplish the former goal more often than the latter, but they do often contain a grain of scientific truth at their core. And, of course, the organization’s Luxuriant Flowing Hair Club for Scientists™ is an indispensable institution on the international scientific landscape.
For your reading pleasure, we bring you an (admittedly unscientific) list of the 5 most improbable research projects from the Annals:
How did Fiorella Gambale, a scientist at the (nonexistent) Institute for Feline Research in Milano, Italy, answer this age-old question? Simple: she dropped the cat Esther 100 times each from a variety of heights and charted the results. Improbably, the cat landed on its feet all 100 times when dropped from 2, 3, 4, 5 or 6 feet, but failed to do so even once when dropped from 1 foot.
Although these results were never vetted by other scientists—so there’s no way of knowing whether Gambale actually performed the tests—the finding that cats really do land on their feet when dropped from more than 12 inches from the ground actually does jibe with established scientific beliefs. The explanation is that they need a few seconds of free fall to trigger their righting reflex, which allows them to bend their back and twist their torso to orient their feet towards the ground.
“The field of culinary evolution faces one great dilemma,” wrote Joseph Staton, of Harvard’s Museum of Comparative Zoology. “Why do most cooked, exotic meats taste like cooked Gallus gallus, the domestic chicken?” Staton tasted a wide variety of meats (including kangaroo, rabbit, goose, pigeon, and iguana) in exploring the question, and ultimately determined that the quality of “chicken taste” is a conserved trait, something that came about once in the evolutionary history of invertebrates and was passed on to many species.
Sadly, Staton’s attempt to sample dinosaurs was thwarted: He apparently made several calls to Chicago’s Field museum to “borrow merely a single bone” from their T. rex but his request was “entangled in red tape.”
A team of geologists from Texas State and Arizona State Universities addressed this very serious question with the cutting-edge tools of their field: digital elevation analysis software, complex mathematical equations, and a standard-size flapjack from the local IHOP. They found that Kansas is, in fact, considerably flatter than an average pancake, which is actually more rugged than the Grand Canyon when viewed up close. They write that Kansas, on the other hand, “might be described, mathematically, as ‘damn flat.’”
Comparing these two fruits is not quite so difficult, it turns out, when you have access to a Nicolet 740 FTIR spectrometer, which can precisely measure the frequencies of light emitted from any substance. Scott Sandford, a NASA researcher, put this device to use on dried samples of a Granny Smith apply and Sunkist orange that had been pulverized and compressed into pellets. He found that the spectrums of light emissions from the fruits were remarkably similar, a rather stunning revelation given how frequently people employ the what he calls the “apples and oranges defense”: that we should avoid comparing two different things because of how different the fruits are.
“It would appear that the comparing apples and oranges defense should no longer be considered valid,” Sandford wrote. “It can be anticipated to have a dramatic effect on the strategies used in arguments and discussions in the future.”
Alice Shirrell Kaswell, a staff member at the Annals of Improbable Research, definitively answered this question once and for all in 2003: The chicken, it turns out, came approximately 11 hours before the egg. Kaswell came to this finding by separately mailing a dozen eggs and one (1) live chicken via the U.S. Postal Service from Cambridge, Massachusetts to New York City. Both items, sent out on a Monday, arrived on Wednesday, but the chicken was delivered at 10:31 a.m., while the eggs didn’t arrive until 9:37 p.m. Problem = solved.
June 10, 2013
The smell of pungent urine may make humans wrinkle their noses, but white-tailed deer don’t mind it. In winter months, they crowd together in northern Michigan–sometimes 100 animals per square mile–and pee all over everything. All of that urine, it turns out, does more than just create an excess of yellow snow. It directly impacts the ability of plants the deer depend on for survival to grow, meaning the animals may be peeing themselves out of their own winter havens.
Researchers typically think of deer’s impact on the environment in terms of the plants they eat. Usually, the animals “simplify” those plant communities with their munching–in other words they eat up all the plants, so only the heartiest species can survive. But it seems the story may be a bit more complicated than that. Though their nitrogen-rich urine–and, to some extent, their feces–they are increasing the complexity of plant communities by helping a multitude of species flourish–perhaps to their own detriment.
For wildlife managers whose job it is to ensure the forest can support deer well into the future, this is a significant consideration. “It’s important to keep ecological context in mind when discussing deer habitat sustainability,” said Bryan Murray, a doctoral candidate in environmental science at Michigan Technical University, in an email.
Murray and colleagues arrived at these findings after performing experiments with deer living in Michigan’s upper peninsula. Long, bitter winters can dump around 250 inches of snow in the region, so deer survival depends upon finding enough to eat and keeping warm in the frozen landscape. Areas of the forest that contain a mix of trees such as eastern hemlock, northern white cedar and balsam fir provide shelter from the wind and some snowfall with their broad, strong branches and bushy needles. Researchers refer to these deer hot-spots as “deeryards.”
The researchers decided to investigate how deer may be impacting the environment during those times of winter crowding. They fenced off three patches of forest to prevent deer from visiting those areas, then compared those deer-free sections with three other patches where that animals continued to congregate. Over the course of the year, they found that the deer significantly influenced the types of plants that grew in those patches, thanks to the nitrogen they excreted in their urine and feces.
Or, in sciencey-speak: “Our results suggest that browsing ungulates affect spatial patterns of herb-layer cover and diversity through the excretion of nitrogenous wastes in small, discrete patches,” lead author Murray and his colleagues report in the journal Ecology.
How, exactly, do the deer influence what grows in their vicinity? During the winter, the high concentration of deer in specific areas mean that the soil underfoot becomes saturated with pee. Nitrogen from the deer’s wastes builds up in the soil, and when spring arrives, the chemical acts like fertilizer, encouraging the growth of some nitrogen-loving plants, including hardwood seedlings. If this pattern repeats itself over a number of years, the conifer-filled deeryards may disappear, replaced by different types of trees that may not do as good of a job blocking wind or catching snow.
In the past, fewer deer congregated in this area of the upper peninsula, but logging and development are forcing more deer to crowd into smaller and less favorable spaces with smaller numbers of viable deeryards. This creates a potentially vicious cycle of crowding “where deer fertilize the soil, plant productivity increases, more deer are attracted to the habitat, fertilizing the soil, and so on,” Murray says.
So it seems that the deer themselves could wind up playing a part in their own undoing by wetting their winter beds.