Microbes redirect our best-laid plans

Greeks at War (pottery from the British Museum; photo courtesy of Wikimedia Commons)

The madness of King George

Timeline, 2006: It’s not that unusual for disease to alter the course of history–or, history as humans intended it to be. Some scholars believe, for example, that the intransigence of King George III of England arose from his affliction with porphyria, a heritable metabolic disorder that can manifest as a mental problem, with symptoms that include irrational intractability. But it’s rarer for a disease to shift the balance of power so entirely that one nation gains the upper hand over another. Yet that appears to be what happened to the city-state of Athens just before the Peloponnesian Wars of around 430 B.C. The upshot of the wave of disease and the wars was that Sparta conquered Athens in 404 B.C.

Spartans had a little microbial assistance

Sparta may have owed its big win to a small bacterium, Salmonella enterica enterica serovar Typhi, the microbe responsible for typhoid fever. A plague swept across Athens from 430 to 426 B.C., having traveled from Ethiopia to Egypt and Libya before alighting in the Greek city and destroying up to a third of its population. In addition, it brought to a close what became known as the Golden Age of Pericles, a time when Athens produced some of its most amazing and widely recognized art, artists, and philosophers, including Aeschylus, Socrates, the Parthenon, and Sophocles. Pericles was a statesman who oversaw the rebuilding of Athens following the Greek win in the Persian Wars, and he guided the city-state to a more democratic form of rule and away from the dictatorships of the previous regimes. In the process, the city flourished in art and architecture.

And then along came the plague. The Greek historian Thucydides, who chronicled the Peloponnesian Wars, left behind such a detailed account of the plague, its symptoms, and what happened to its victims, that intrigued medical detectives have ever since debated about what might have caused it. Thucydides, himself a plague survivor, vividly described the sudden fever, redness of the eyes, hemorrhaging, painful chest and cough, stomach distress, and diarrhea that ultimately led to death in so many cases. He also mentioned pustules and ulcers of the skin and the loss of toes and fingers in survivors. This litany of symptoms produced many candidate causes, including bubonic plague, anthrax, smallpox, measles, and typhoid fever.

Construction crews yet again uncover something interesting

In the mid-1980s, a construction crew was busy digging a hole for a subway station in the city of Kerameikos when they uncovered a mass burial site. Unlike other Greek burial sites, this one bore marks of hasty and haphazard burials, and the few artefacts that accompanied the bones dated it to the time of the plague that destroyed Athens. Researchers were able to harvest some teeth from the site and analyze the tooth pulp, which retains a history of the infections a person has suffered. They examined DNA sequences from the pulp for matches with suggested microbial agents of the plague, and finally found a match with the typhoid bacterium.

Typhoid Mary: Intent on cooking, ended up killing

One discrepancy between the disease pattern of typhoid fever and that described by Thucydides is the rapidity of onset the Greek historian detailed. Today, typhoid fever, which still infects millions of people worldwide, takes longer to develop in an infected individual, and sometimes never develops at all. People who bear the virus but don’t become ill themselves are “carriers.”

Perhaps the most famous carrier was Typhoid Mary, Mary Mallon, a cook in New York City at the beginning of the 20th century. It is believed that she infected hundreds of people, with about 50 known cases and a handful of deaths being directly associated with her. Typhoid Mary was told not to work as a cook any longer or she would be quarantined, but she simply disappeared for awhile and then turned up under a different name, still working as a cook. After another outbreak was traced to her, she was kept in quarantine for 23 years until she died.

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The narwhal: a serious case of nerves

"Narwhal or unicorn"

Timeline, 2006: The narwhal has a history as striking as the animal itself. Vikings kept the narwhal a secret for centuries even as they peddled its “horn” as that of a unicorn. Narwhal tusks were so prized that monarchs paid the equivalent of the cost of a castle just to have one. They were thought to have magic powers, render poison ineffective, cure all manner of diseases, and foil assassins.

A tooth and nothing but a tooth

As it turns out, the horn is really just a tooth, an extremely long, odd, tooth. The narwhal tusk, which usually grows only on males from their left upper jaw, can reach lengths of six feet or more. Sometimes, males will grow two tusks, one on each side. The tooth turns like a corkscrew as it grows, stick straight, from the narwhal’s head. They are such an odd sight that scientists have been trying to figure out for centuries exactly what that tusk might be doing there.

Some have posited that the narwhal uses the tusks in epic battles with other male narwhals. Others have fancifully suggested that the animal might use the long tooth to break through the ice, ram the sides of ships (nevermind the disconnect between when the tusk arose and when ships entered the scene), or to skewer prey—although no one seems to have addressed how the narwhal would then get the prey to its mouth.

Gentle tusk rubbing

The facts are that the narwhal rarely, if ever, appears to duel with other narwhals. Its primary use of the tusk appears to be for tusking other males, in which the animals gently rub tusks with one another. They also may be used in mating or other activities, although that has not yet been demonstrated. But what has been discovered is that the narwhal ought to be suffering from a severe case of permanent toothache.

Arctic cold strikes a narwhal nerve

Anyone who has ever had exposed nerves around their teeth knows that when cold hits those nerves, the pain usually sends us running for the dentist. Now imagine that your tooth is six feet long, has millions of completely exposed nerve endings, and is constantly plunged in the icy waters of the Arctic. You’ve just imagined being a narwhal.

Dentist on ice

A clinical instructor at the Harvard School of Dental Medicine who thinks of nothing but teeth made this discovery about the narwhal. The instructor, Martin Nweeia, can wax rhapsodic about teeth and how central they are to our health and the stories they can tell even about how we lived and died. He has carried his tooth obsession beyond his own species, however; his passion led him to spend days on Arctic ice floes, watching for the elusive narwhal, or at least one of the tusks, to emerge from the deadly cold water. He also befriended the local Inuit, who rely on the narwhal as a source of food and fuel oil.

His fascination and rapport with the Inuit people ended with his viewing several specimens of narwhal tusks. What he and his colleagues discovered astonished them. The tusks appeared to consist of open tubules that led straight to what appear to be millions of exposed nerve endings. In humans, nerve tubules are never open in healthy teeth. But in the narwhal tusk, which is an incredible example of sexual dimorphism and the only spiral tooth known in nature today, these open tubules were the norm.

Sensory tooth

The researchers speculated that the animals may use this enormous number of naked nerves as a finely sensitive sensory organ. In addition, it is possible that the teeth transmit voltage through a process called the piezo effect, in which crystals generate voltage when a mechanical force rattles them. In the case of the narwhal, who swim quickly through the water, water pressure might provide the force. Because narwhals are among the most vocal of whales, the tusks could also be sound sensors.

Why would dentists be so interested in the tusks of a whale? Examinations of the narwhal tusks have revealed that they are incredibly flexible, unlike our teeth, which are strong but also rigid and comparatively brittle. It is possible that understanding the narwhal tusk might have clinical applications for developing flexible dental materials for restoring pearly whites in people.

Columbus Day post: Failed Columbus settlement found no silver

Christopher Columbus

Columbus may have made his name for the history books by “finding” the Americas, but his real claim to fame may have been his world-class snake oil salesman ability. After returning from his famed voyage of 1492, Columbus bowed before his patrons, Spain’s King Ferdinand and Queen Isabella, and spun a tale of precious metals in the new world. His fairy stories about a land of silver and gold lit a fire under the Spanish royals, leading them to finance a much larger second expedition to the New World Columbus had stumbled on.

Tall tales of silver and gold

His tall tales also attracted a huge crowd of settlers with gold in their eyes and riches on the brain. This hapless group, 1500 strong, landed on the north shore of today’s Dominican Republic in 1494, only to find a land of sand and hardship, not the streets of gold they’d expected. Catastrophe piled on top of catastrophe in the form of hunger, disease, hurricanes, and conflicts with the indigenous people. Mutiny not unnaturally followed, and four years after the settlement was established, the few hundred remaining settlers abandoned the effort and returned home.

This failed first European town in the New World left behind a treasure trove for archaeologists, however. Among the finds was about 100 pounds of galena, a lead ore containing silver. Medieval people used galena to determine how much silver a substance contained. They could create galena with a known amount of silver, or galena could be found and its silver content compared with galena containing the known amount of ore.

Why is all this galena lying around?

For many years, scholars had thought that the galena found at the settlement, which its founders had called La Isabela after the financier queen, was the result of the settlers’ discovery of silver in the area. The odd thing was, no settler ever left a written record of such a discovery. Given the 100 pounds of it and the detailed records people on such expeditions tended to leave, such a find usually would have earned a mention.

In addition to the pounds of galena, researchers also found several hundred pounds of slag, which turned out to be lead silicate with flecks of silver in it. This slag also could have been the result of settlers’ attempts to extract silver from a local discovery. But again, there was no mention in the record of what would have been a significant operation, given the 400-plus pounds of slag. The galena and slag were discovered near a building that was used to store royal property.

Starving and desperate for silver

To address the discrepancy between the written record and archeological inference, a group of researchers applied chemical analysis to the galena and slag and compared it to known samples of Caribbean ores. They found that the galena and slag did not come from a Caribbean location and instead probably traveled with the settlers from Spain. The researchers speculate that the settlers, starving and desperate, were frantically trying to extract silver from items in the royal coffers.

Supporting this idea is the fact that the lead in the galena would normally have been more useful to them, for things like musket balls or supports for a ship. The waste, in the form of the lead silicate slag, was of no use to them at all.

An expert in medieval chemistry told the researchers that people of that era commonly mixed galena with ores they thought might contained a precious metal, using galena with a known quantity as a marker for how much gold or silver their discovered ore contained. This explanation may provide the reason the settler had galena with them in the first place.

Did division of labor defeat the Neanderthals?

According to some anthropologists, the classic depiction of Paleolithic man as a few strapping cavemen ganging up on a mammoth with their spears might need to be replaced with dioramas of women gathering seeds or a man scraping an animal carcass from the ground to take home for dinner. In addition, this division of labor between men and women may have given Homo sapiens the upper hand when it came to their competition with Neanderthals in the Upper Paleolithic, about 45,000 to 10,000 years ago.

You may be familiar with some of the usual reasons proposed for the extinction of the Neanderthals and the supremacy of H. sapiens in the competition for resources: The wily H. sapiens swarmed the Neanderthals, defeating them in war with superior weaponry or a greater ability to resist disease or defy climate change. Some experts have proposed that a combination of these climatological and cultural factors may have contributed to the Neanderthal’s loss. But until now, no one had focused on differences in division of labor as giving H. sapiens the advantage.

The crushing hand of the Neanderthal woman

Evidence shows that Neanderthal men and women may have shared similar robust builds. In addition to bone finds that suggest as much, a researcher who focuses on hand mechanics has found that the Neanderthal female hand could exert as much force as that of a male. In addition, Neanderthal home sites rarely include artifacts such as tools for grinding seeds or trapping small animals, or even evidence of clothing production, such as needles. Thus, it seems that the Neanderthals may have, as a group—men, women, and children—spent their time focusing on one thing: big game.

Hunting a large animal that has defense ranging from tooth to antler to hoof to claw is a dangerous business, more so when your only weapon is a pointed stone attached to the end of a stick. Neanderthals got a big payoff when their spears worked, however, in the form of calorie- and protein-rich meat for the group. Evidence suggests that the whole group participated in this dangerous task—the bones of females as well as males bear the signs of many fractures, possibly the result of this dangerous lifestyle. Women and children may have been responsible for driving game or forging escape routes should the angered and frightened animal have turned on the group.

The pitfalls of group big-game hunting

This focus on a single kind of food source can have predictable consequences. In times of scarcity, the Neanderthals lacked other options. If they had no training or skills to obtain other food sources, then scarce big game translated into scarce Neanderthals. Homo sapiens, on the other hand, may have developed a division of labor between men and women before emerging from Africa 150,000 years after the Neanderthals, equipped with women who knew how to make protective clothing, trap small animals, and collect and prepare seeds and vegetation, and men with advanced weaponry who could efficiently hunt game. In addition, these people may have relied on scavenging as well as hunting to boost their food supply.

Division of labor gave H. sapiens the upper (non-crushing) hand?

The division of labor, which in some societies was reversed or not allocated in the same way between men and women, allowed Homo sapiens to adjust when food was scarce and boom when food was plentiful, or so some researchers now argue. These archaic humans could use their clothes-making skills to handle climate change and their efficient allocation of time resources to bring in food simultaneously from different sources, even when times were tough. Their booming population may have given them the numbers they needed to outcompete the Neanderthals.

…Or maybe not

Some researchers disagree with this hypothesis, suggesting that evidence of a division of labor dates back one or two million years, and there have been some predictable references in the news media to men’s and women’s roles today. One of the authors of the “division of labor” study explicitly cautions that what was beneficial 40,000 years ago isn’t necessarily a guide to what is beneficial today. Traits that provide a competitive edge are after all entirely reliant on context: What’s good in one environment may not necessarily be that helpful in a different set of circumstances.

Ancient Peruvian beer breweries

Rich Peruvian women brewed beer

When it comes to drunken women, the Peruvians have always been different. In many societies, women are not supposed to drink at all. They certainly aren’t supposed to get knee-walking, rip-roaring drunk, matching shot for shot with a man. It’s generally considered unladylike, and these days, studies keep coming out indicating that overimbibing may have more adverse effects on women’s health than it does on men’s.

But the Peruvians of today, especially those living in the Andes, indulge in equal-opportunity carousing. It appears that they simply are following a tradition that may be more than 1000 years old.

What drove agriculture? Beer or bread, naturally

A few years ago, archaeologists discovered large broken vats on top of a 8000-foot-high mesa, Cerro Baul, in the Peruvian Andes. Among the vats were the remnants of smaller vessels and some shawl pins that belonged to noblewomen of the Wari people, a pre-Incan civilization that suddenly disappeared about 1000 years ago. From about 600 AD to 1000 AD, however, the civilization flourished around Cerro Baul. Nobles lived on the mountaintop, and farmers and middle-class artisans and technicians lived and worked in the valleys below.

The researchers felt that they must have stumbled across one of the world’s ancient breweries. Breweries attract anthropologists and historians because beer competes with bread as the driving force behind the development of agriculture. Every civilization appears to have brewed, usually using grains like wheat and barley. Some of the oldest suspected breweries date back as far as 3000 BC in Egypt, and suspected breweries have also been discovered in what is now Iraq.

But the equivocal “suspected” is what makes the Peruvian find so delicious. Ancient breweries defy clear identification because the beer was brewed from the same grains used to make bread; thus, it is difficult to distinguish the cereal-based residue on pot fragments as the result of brewing vs. baking. What the brewery-hunters of the world needed was a civilization that used some unusual ingredient in its beer, something that they didn’t also use in their bread. And they found it in the Wari people of ancient Peru.

Corn fermented, pepper-flavored beer

Even today, native Peruvian beer stands out among the world’s brews. It is fermented from corn and flavored with berries from the pepper tree. No other beer in the world has this combination, and the Peruvians apparently do not use the pepper tree to make bread. This concoction, called “chicha” today, is apparently very like what the Wari people brewed high on their mesa 1000 years ago.

The researchers latched onto pepper tree residues as the ingredient that would allow them to definitively identify an ancient brewery. The pepper berries contain a compound called oxalic acid that can adhere to ceramic pottery for centuries. Using techniques like liquid chromatography, they were able to confirm that this compound was indeed present in the large vats on Cerro Baul.

Wild, ancient Peruvian bacchanal

They had suspected as much. The vats themselves were huge and obviously designed to hold liquid. The surprise was that the brewery and the vats appeared to have been destroyed in a single night of carousing just before the Wari abandoned their mountaintop. Researchers surmise that the nobles of the town engaged in ritual drinking and drunkenness—the big guns got the larger Wari beer steins—and then, when the ceremony ended, they destroyed their ceramic vats and set the place on fire. After the building had burned to the ground, the nobles placed jewelry on top of the remains, possibly to identify it as a sacred place.

Interestingly, among the destruction, the archaeologists found the noblewomen’s shawl pins. They surmise that the women may have brewed the beer; in later Incan civilizations, upper-class women brewed beer, and only upper-class people drank chicha with the pepper-tree flavor added.

Of course, you have to taste test it

When it was active, the brewery may have produced hundreds of gallons of beer a week. In an effort to experience the flavor, some archaeologists recreated the ancient concoction and report that it is not quite as dark as a modern-day stout, and has sweet, peppery flavor with a bitter finish.

The lovely bones: Terra preta to save our terra firma?

Charred bones set to save the world?

The Amazon river basin is home to the famous Amazonian “dark earth,” or terra preta, which recently made the news as more proof of large civilizations in the tangled Amazon forests.  This soil is renowned for its fertile properties, its loose consistency, water-holding abilities, and of course, its dark color. The people who used this earth generations ago—as many as 3000 years ago, according to one researcher—may have had no active interest in “greening” the planet, but they were very interested in getting a good crop yield for their efforts. Terra preta probably gave them just that.

Ancient farming wisdom

Somewhere along your educational path, you may have learned a few tips about farming. Rotate your crops. Let fields take a break. Till the soil. What you may not have understood as clearly were the natural processes that drove this farming wisdom.

When farmers turn over the soil, they loosen it. Earth happens to be the largest sink of carbon on terrestrial Earth, and when we move it around, some of that carbon gets released. When we try to fertilize it using dead and decomposing organic matter—compost, manure—this approach works in the short term to restore some nutrients, but microorgansims make pretty quick work of these organic remnants, returning carbon to the atmosphere again as carbon dioxide.

Thus, standard farming techniques of tilling and fertilizing and applying manure are short-lived efforts to keep the soil nutrient rich enough for planting. If nutrients are low, crop yield will be, too. And then there’s the water consideration; if the soil holds too little water or too much, that will also affect crop yield.

Magical fairy dust for crops

These factors all combine to make the terra preta soil look like magical fairy dust for crops. The soil actually is charcoal—or, in the lingo of the scientists who work with it, biochar. It is made from the rapid, pressurized burning of dead stuff—bones, tree bark—and manure. Pack it all into a metal container with a little hole for some pressure to escape, heat it to about 400 degrees Celsius, and you’ve made yourself some biochar. It apparently looks just like the charcoal you’d use at a cookout, but it has many more uses.

The carbon in the biochar is pretty inaccessible to microorganisms that would break it up, so it lasts a lot longer in the soil than your average, uncharred manure. In fact, it’s so long lasting that it’s still around in the Amazonian river basin long after the ancient farmers who used it disappeared. In addition to being a nutrient-rich and nutrient-tight source of carbon, biochar also is quite grabby with water, holding much more water than your average soil sample. That feature means that less water is required to grow crops in a biochar-laced field than would be needed in a regular, every-day kind of field.

Could soil invented in the Amazon save the Amazon?

Plants growing in the stuff do so faster, more robustly, and in greater numbers, primarily because of the rich nutrient source the biochar provides. Research indicates that the optimum combination is biochar plus fertilizer, which gives the greatest crop yield compared to either alone or neither. Using biochar could dramatically enhance global crop yields while decreasing water use and without adding a single acre of cropland. Using soil invented in the Amazon to save the Amazon rainforest has a nice “the circle is complete” aspect to it.

Although biochar has the drawback of having to be made and transported, its benefits to the planet don’t end with crop yield and water savings. The smoke generated from its preparation, in a process called pyrolysis, can be collected and used to form bio-oil, a form of renewable energy. In addition, biochar has potential as a sponge to soak up phosphates and nitrates from fertilizers before they reach our waterways, a sort of barrier against pollution. Last, this dark, magical fairy dust not only reduces carbon dioxide emissions from cropland but also significantly decreases methane and nitrous oxide emissions, both greenhouse gases that are far more potent than carbon dioxide but get considerably less press.

The piggish origins of civilization

Follow the pig

For researchers interested in tracing the path of human civilization from its birthplace in the Fertile Crescent to the rest of the world, they need only follow the path of the pig.

Pig toting

Until this research was reported, humans agreed that pigs had fallen under our magical domestication powers only twice about 9,000 years ago, once in what is called the Near East (Turkey), and a second time in what is called the Far East (China). Morphological and some genetic evidence seemed to point to these two events only. That led human geographers to conclude that humans must have toted domesticated pigs around from the Far or Near East to other parts of the world like Europe or Africa, rather than domesticating the wild boars they encountered in every new locale.

Occam’s Razor violation

As it turns out, those ideas—which enjoyed the support even of Charles Darwin—were wrong. And they provide a nice example of a violation Occam’s Razor, the rule that scientists should select the explanation that requires the fewest assumptions. In the case of the pig, two domestication events definitely required fewer assumptions than the many that we now believe to have occurred.

Research published in the journal Science in 2005 has identified at least seven occurrences of the domestication of wild boars. Two events occurred in Turkey and China, as previously thought, but the other five events took place in Italy, Central Europe, India, southeast Asia, and on islands off of southeast Asia, like Indonesia. Apparently, people arrived in these areas, corralled some wild boars, and ultimately domesticated them, establishing genetic lines that we have now traced to today.

As usual, molecular biology overrules everything else

The scientists uncovered the pig domestication pattern using modern molecular biology tools. They relied on a genetic tool known as the mitochondrial clock. Mitochondria have their own DNA, which they use as the code for their own, specialized mitochondrial proteins. Because mitochondria are essential to cell function and survival, changes in DNA coding sequences are rare because selection pressures against them are strong. For this reason, any changes are usually random changes in noncoding regions, changes that accumulate slowly and at a fairly predictable rate over time. This rate of accumulation is the mitochondrial clock, which we use to tick off the amount of time that has passed between mutations.

Tick-tock, mitochondrial clock

Very closely related individuals will have almost identical mitochondrial sequences; for example, the mitochondria that you have are probably exactly alike in sequence to the mitochondria your mother has. You inherited those mitochondria only from your mother, whose egg provided these essential organelles to the zygote that ultimately became you. Were someone to sample the mitochondria from one of your relatives thousands of years from now, they would probably find only a few changes, but if they compared this sample to one from someone unrelated to you, they would find different changes and a different number of changes, indicating less of a relationship.

That’s how the researchers figured out the mystery of the pigs. They sampled wild boars from each of the areas and sampled domestic pigs from the same locales. After comparing the mitochondrial DNA sequences among these groups, they found that pigs in Italy had sequences very like those of wild boars in Italy, while pigs in India had sequences very like those of wild boars there.

Approachable teenage-like pigs

How did we domesticate the pigs? Researchers speculate that adult boars (males) who still behaved like teenagers were most likely to approach human settlements to forage. They were also less aggressive than males who behaved like full adults, and thus, easier to domesticate. They fed better on human food scraps than did their more-mature—and more-skittish—brethren, and enjoyed better survival and more opportunities to pass on their juvenile characteristics, which also included shorter snouts, smaller tusks, and squealing, to their offspring. Domestication was just the next step.

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