Mysterious sounds, ancient migrations, and worms vs mosquitoes

NPR: On the unlikely source for what could be the next big mosquito repellent
Jonathan Lambert

The next great insect repellent might come from a strain of bacteria that lives inside a common parasitic worm.

Really, I could just stop right there, because I can already hear people doing the nope, nope, nope. But consider this a real contest between what creeps you out more — smearing something on your skin that comes from parasitic worm bacteria, or … mosquitoes. Personally, I’m ready to bring on those worm germs.

A study published Wednesday in Science Advances has found that a compound derived from these bacteria is three times more potent than DEET in repelling mosquitoes. More research must be done to demonstrate its safety, but this bacterial chemical could play an important role in the fight against mosquito-borne illness.

The bacteria  in this case is called Xenorhabdus and it resides in microscopic roundworms known as nematodes. But it’s not the only bacteria living in an unlikely place that might have potential gppd things to share with human beings. One Sir Not-Appearing-In-This-Article wold be Wolbachia. It’s a symbiotic bacteria found in more than half of all insect species — making it possibly the single most common infectious bacteria on the planet. And one of the things Wolbachia does for insects is protect them against viral infections. There are a number of studies underway to see if it, or compounds derived from it, might do the same thing for us.

National Geographic: An ancient reptile with a surprisingly advanced walk.
Jason Bittel

Three hundred million years ago, Earth was home to a strange creature the size of a small dog called Orobates pabsti. Most people won’t know its name, but scientists consider the animal to be a close cousin to the last common ancestor of reptiles, dinosaurs, birds, and even mammals.

Now, scientists not only know that O. pabsti walked the Earth, they also know how it would have walked.

The cool thing about the Orobates is that it left behind both bones and footprints. By pairing the two, scientists can get a real sense of how it moved, from its gait to its speed. Considering the age of this genuinely ancient reptile — we’re talking all the way back in the Pennsylvanian, about as far before the dinosaurs as we are after the (non-feathery) dinosaurs — scientists had expected a clumsy waddle. The impression of everything that old has long been that they moved slowly along, limbs spread out wide, like giant salamanders move today.

That’s not what they found.

Eventually, the team settled on a caiman-like gait as the most probable match. But just to make sure their methodology was sound, they went back and did the same experiment for living species of caiman and salamander, to see if they could predict how those animals would move using only footprints and digital skeleton models. When these tests produced gaits like those seen in nature, they knew they were on to something.

Caimans — alligator relatives — may not strike us as particularly modern, but they didn’t show up until about the same time as the dinosaurs. So they’re the new kids. 

This is just one of many results that shows that the world on the other side of the “Great Dying” at the end of the Permian Period was surprisingly advanced, diverse, and filled with unexpected creatures.


New York Times Magazine: Casts a critical eye at the research on ancient human DNA.
Gideon Lewis-Kraus

In his recent book, Reich ranks the “ancient-DNA revolution” with the invention of the microscope. Ancient DNA, his research suggests, can explain with more certainty and detail than any previous technique the course of human evolution, history and identity — as he puts it in the book’s title, “Who We Are and How We Got Here.” Though Reich works with samples that are thousands or tens of thousands of years old, the phrase “ancient DNA” encompasses any old genetic material that has been heavily degraded, and Reich’s work has been made possible only by a series of technological and procedural advances. Researchers in the field ship or hand-carry the bones to Harvard, where clean-suited technicians expose them to ultraviolet light to prevent contamination, then bore holes in them with dental drills. These skeletal remains are often rare — one pinkie-finger fragment that researchers in a lab in Leipzig used to demonstrate the existence of a long-extinct form of archaic humans was one of only four such bones ever found. Minuscule portions of genetic code are isolated and enriched, then read by expensive sequencers; statistical techniques then plot the relationship between this particular sample and thousands more in enormous data sets.

This is a fascinating, and lengthy, piece that moves from the general — how DNA research is changing our views of human migrations — to the specific, in this case a research project in the South Pacific. It reflects the way two different groups of researchers, those used to tracking cultures through artifacts and culture, and those ready to turn to crank up the gene sequencer, can generate very different results. It also hints at how just because something came from a lab, doesn’t mean it did come loaded down by expectations. That’s true in court cases, and in archaeology. It’s all too easy to produce headline-generating results, from either camp of researchers, when those results are done in a vacuum without consideration of how they fit into a pattern.

In October 2016, the paper — with such well-regarded Pacific archaeologists as Stuart Bedford and his mentor, Matthew Spriggs of the Australian National University, among the 31 authors — was published in Nature as “Genomic Insights Into the Peopling of the Southwest Pacific.” The analysis of ancient DNA from three 3,000-year-old skulls from Teouma, along with one skull dated a few hundred years later from Tonga, appeared to provide unambiguous confirmation of Lapita heritage. The First Remote Oceanians, as the paper calls them, were not, after all, a heterogenous group; they were of unmixed Asian descent.

When you find Earth shaking results … give it another shake. Give this lengthy, but well-written piece a read. This is popular science writing at its best. Highly recommended.


As usual, the image comes from Andy Brunning at Compound Interest. Visit his site for a larger, easier to read version — you’re really going to need it this week.

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