News and notes about science
A HUGE FAMILY TREE EXPOSES THE HISTORY OF KISSING COUSINS
Before the Industrial Revolution in the United States, Canada and Europe, you might have ended up married to a fourth cousin. People didn’t travel far to find a spouse, and the closer you were to home, the more likely it was you’d marry within your family.
Then, in the late 19th century, something changed, and people stopped marrying their cousins.
It has been conventional wisdom that Europeans and North Americans married more outside their families as geographic dispersal ramped up between 1825 and 1875, with the advent of mass railroad travel. But over the same period, the genetic relatedness of many couples actually increased. It wasn’t until after 1875 that partners started to become less and less related.
This 50-year lag might indicate that shifts in social norms played a bigger role than geographic mobility in getting people to wed outside their bloodline. It’s also just one example of the insights that can be gleaned from the world’s largest, scientifically-vetted family tree, presented in a study published March 1 in Science.
Compiling and validating 86 million public profiles from Geni.com, a genealogy-driven social media site, the authors generated 5 million family trees. The largest tree consisted of 13 million people and spanned an average of 11 generations.
The researchers then used this data set to test several genetic and historical hypotheses, showing “you can harness the hard work of so many people around the globe just documenting their own family history, and learn something about humanity,” said Yaniv Erlich, chief science officer of MyHeritage, the parent company of Geni.com, and senior author of the paper.
But it’s important to consider that not everyone is represented equally.
In addition to likely underreporting infant mortalities and people who never bore children, genealogy data skews toward families that have the privilege of accessing and maintaining a detailed history, said Emily Klancher Merchant, a science and technology studies professor at the University of California, Davis. Sites like Geni.com require a paid membership to access all features. And families that were forced to migrate, through the slave trade or to flee persecution, are probably not as well-represented in their databases. Steph Yin
HEALTHY AS CAN BE, BUT WITH WORMS INSIDE
Seventeen volunteers in the Netherlands have agreed to host parasitic worms in their bodies for 12 weeks to help advance research toward a vaccine for schistosomiasis, a chronic disease that afflicts more than 200 million people a year, killing thousands, primarily in sub-Saharan Africa and South America.
“Yes it sounds odd and crazy. The idea of having a worm grow inside you is awful,” said Meta Roestenberg, an infectious disease physician at Leiden University Medical Center, who is directing the research. But she said the risk to the student volunteers is “extremely small.” A Dutch ethics board agreed.
But other researchers of this disease are conflicted about the study’s method, fearing there is no way to be sure that all of the tiny parasites
have been evicted from the hosts when the trial ends.
Schistosomiasis is sometimes called bilharzia or snail fever because the illness-causing larvae spend their nights tucked away in the shells of snails in freshwater lakes. During daylight, thousands of Schistosoma mansoni head out across the water, penetrating the skin of bathers or fisherman. Over the coming weeks, larvae turn into adult worms and males and females pair up and mate, producing hundreds of eggs a day.
When the offspring hatch, some may get lodged in the liver or bladder, inducing an immune response that can lead to chronic pain, fever, organ failure, internal bleeding or a gynecological infection that many researchers believe dramatically increases the risk of being infected by HIV.
At least two potential vaccines for “schisto” were recently approved for early stage human trials. The traditional path forward, which would cost millions, requires setting up a study in an afflicted area and using only people who have already been exposed to the worms.
“You get yourself in a Catch-22,” said Dr. Peter J. Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine in Texas. Donors, he said, want proof that the vaccine will work in people before committing funds. But it is hard to offer proof without money.
Roestenberg’s study aims to prove that there is a quick and affordable way to test the vaccine in people. That could help the prototype Hotez has developed with Texas Children’s Hospital Center for Vaccine Developmentadvance more quickly.
Each volunteer was paid about $1,200. Heather Murphy
INSIDE WOUNDED FLIES, FAT CELLS RACE TO THE RESCUE
Anna Franz, a biochemist at the University of Bristol in Britain, was studying how a fruit fly’s immune cells respond when the insect is wounded. Under the microscope, she noticed cloudlike shadows moving toward a lesion. Because of their size, she suspected the shadows might be fat cells, which can be 5 to 10 times bigger than other cells found in fruit flies.
But how could these cells — which are conventionally believed to have no ability to move themselves around — make such an unlikely journey? And why?
Biologists have long believed that fat cells lead sedentary lives, unable to move themselves around the body once they get settled. But new research suggests that fruit fly fat cells have greater mobility, and are therefore more helpful in an emergency than previously thought. And that could have implications for how we think about fat cells in other organisms, including ourselves.
Franz and two colleagues used lasers to make small lacerations in the thoraxes of fruit flies, where very few fat cells reside. To their surprise, they found that a handful of fat cells not only arrived at the wound within minutes, but performed vital functions once they got there.
First, the fat cells used their mass to plug the wound, then pushed harmful debris to the edges, where immune cells were waiting to dispose of them. “It’s like a cleaner, sweeping the stuff to the side,” said Paul Martin, a co-author of the study, which was published last week in the journal Developmental Cell. “Then, the immune cells are all hanging out at the edge clearing the debris. So it’s a collaborative effort.”
The fat cells also produced an antimicrobial substance that may help stave off infection as the fruit flies heal.
Cells typically move by using tiny filaments that help them push and pull off other objects. But the fat cells appeared to swim through fluid by flexing and relaxing a pair of proteins, actin and myosin, which are found in muscle fibers.
To confirm that the actin and myosin were facilitating the movement, the researchers created genetically modified versions of the cells in which those proteins were inactive. Those cells were not able to move on their own. Douglas Quenqua
NO SIGN OF NEWBORN NORTH ATLANTIC WHALES THIS BREEDING SEASON
The North Atlantic right whale is one of the most endangered creatures and all indications are its situation is rapidly getting worse.
At last count, the entire population was estimated to include just 458 animals, and at least 17 of them died last year. Now, researchers tracking the right whale’s normal calving grounds, from Georgia to Florida, said they have seen no signs of newborns yet this year, at a time when mothers would normally be birthing and nursing.
The National Oceanic and Atmospheric Administration estimates that at least 411 calves were born from 1990 to 2014, an average of about 17 a year. But only five were born in 2017, and if there really are no newborns this year, that would be “unprecedented,” said Charles “Stormy” Mayo, director of the Right Whale Ecology Program at the Center for Coastal Studies in Provincetown, Massachusetts.
It’s possible, Mayo said, that the animals have simply moved elsewhere to give birth, and that at least a few new calves will be found later in the season.
“I will not be surprised, though I will be excited, if we see a calf or two in Cape Cod Bay,” said Mayo, whose research team tracks the animals in the bay.
Researchers fly over Cape Cod Bay daily this time of year, following and counting the animals. So far, he said, they have seen an unusually large number of animals, including females of reproductive age, some of whom would typically be farther south with newborn calves.
“Many should be elsewhere,” he said.
Whales are moving in unpredictable ways, Mayo said, because their food is being relocated by changes in ocean conditions.
Unusually high numbers of right whales turned up in Canada’s Gulf of St. Lawrence last summer, for instance, where they were not expected. The vast majority of animals known to have died were struck by ships or injured by lines set by fishermen, who didn’t expect them to be in the gulf.
From 2010 through 2014, nearly six whales a year on average were killed or severely injured, according to NOAA. Last year, at least 17 were killed. Karen Weintraub
KING PENGUINS ARE ENDANGERED BY WARMER SEAS
Their little chicks fast for more than a week while they forage for fish and krill in the waters of the Antarctic polar front, an upwelling where cold, deep seas mix with more temperate seas.
And while king penguins, the second largest penguin species, can swim a 400-mile round trip during that time, they are traveling farther and farther from their nests on the islands near Antarctica, endangering their hungry offspring.
As with so many other species, warmer temperatures are threatening this population, and a new study published in Nature Climate Change warns that 70 percent of the 1.6 million estimated breeding pairs of king penguins could be affected in this century.
“They will need to either move somewhere else or they will just disappear,” said Emiliano Trucchi, one of the paper’s senior authors. “The largest colonies are on islands that will be too far from the source of food,” predicted Trucchi, an evolutionary biologist at the University of Ferrara in Italy.
The research team developed a model to predict which islands would become vulnerable with warming, and which ones might become better habitats. They then validated their model through historical and genetic data.
About half of the king penguin population nests on the Crozet and Prince Edward Islands, in the Indian Ocean south of Madagascar, and are projected to lose their habitat by 2100, according to the model. The 21 percent that nest on the Kerguelen Islands in the Indian Ocean and the Falkland and Tierra del Fuego islands close to South America would find their nesting grounds altered and would have to travel farther to find food and so might relocate. But, the researchers said, some of that would be offset by the colonization of Bouvet Island and a few other islands.
Several others are likely to become more habitable, according to the research. But unlike their bigger cousins the emperor penguins, king penguins can’t nest on ice so their choices are limited and may be hundreds or even thousands of miles from their current nesting areas.