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DNA of Ancient Cats Traces the Path of Their Global Conquest

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A new study of ancient DNA presented at the 7th International Symposium on Biomolecular Archaeology has revealed the secret story of cats’ spread across the globe.

Cats are mysterious creatures. They’re independent yet social, aloof yet endearing, and very good at getting what they want. Like any organism, the very first cats originated in one place, then spread. They spread, and spread, and continue to spread, becoming beloved pets and conservationists’ worst nightmare, often at the same time.

Exactly how they managed this feat of feline world domination has remained something of a puzzle. How did these small, terrestrial animals make it across the oceans? Cats have no value as livestock (like cows) or transport (like horses). They’re good workers as mousers, but only when they want to be. And we talk about the "domestic" cat, but some scientists think that may be a misnomer—maybe we haven’t really domesticated them at all.

But they may have domesticated us. Look back 12,000 years in time to the Fertile Crescent at the dawn of agriculture, when cats were buried along with people. Look to the millions of sacred cats mummified in ancient Egypt. Every time we find the carefully entombed remains of a cat, we find a clue to how they got to be who (and where) they are today.

Researchers lead by Eva-Maria Geigl, an evolutionary geneticist at the Institut Jacques Monod in Paris, sequenced DNA taken from the remains of 209 cats found at more than 30 archaeological digs across Africa, the Middle East, and Europe. They focused exclusively on mitochondrial DNA, which is inherited maternally. The samples represented an enormous swath of history, from our days as hunter-gatherers up through the 18th century.

The cats’ DNA painted a picture of two distinct bursts of kitty scattering (s-cat-tering, if you will). The first was in the Middle East, where farming began about 10,000 years ago. As farming communities grew out toward the Mediterranean Sea, the cats came with them. The study authors say the farms’ piles of grain likely attracted rodents, which then brought out the wild cats. And once farmers saw the value of having fierce mousers around, they likely tried to find a way to keep them.

Fast-forward several millennia to the second wave, when noble Egyptian cats began to sow their wild oats throughout Eurasia and Africa. A family line found in Egyptian mummy cats from the end of the fourth century BCE to the fourth century CE was also found in cats from Bulgaria, Turkey, and sub-Saharan Africa during roughly the same time.

Then they hit up the Vikings. Seafaring life is a tangle of dangers and threats, including the voracious mouths of rats and mice in a hold full of essential provisions. By around the 8th century, Vikings, too, had seen the value of keeping cats around, as evidenced by feline remains found in Viking settlements.

And still they spread. Cats are something of a contentious topic these days. The hunting skills that made them so attractive to our distant ancestors can today make them a serious threat to wildlife. Some places have banned cats altogether, although it might already be too late—they've already got us thoroughly wrapped around their little paws.

[h/t Nature]

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Ted Cranford
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science
Scientists Use a CT Scanner to Give Whales a Hearing Test
Ted Cranford
Ted Cranford

It's hard to study how whales hear. You can't just give the largest animals in the world a standard hearing test. But it's important to know, because noise pollution is a huge problem underwater. Loud sounds generated by human activity like shipping and drilling now permeate the ocean, subjecting animals like whales and dolphins to an unnatural din that interferes with their ability to sense and communicate.

New research presented at the 2018 Experimental Biology meeting in San Diego, California suggests that the answer lies in a CT scanner designed to image rockets. Scientists in San Diego recently used a CT scanner to scan an entire minke whale, allowing them to model how it and other whales hear.

Many whales rely on their hearing more than any other sense. Whales use sonar to detect the environment around them. Sound travels fast underwater and can carry across long distances, and it allows whales to sense both predators and potential prey over the vast territories these animals inhabit. It’s key to communicating with other whales, too.

A CT scan of two halves of a dead whale
Ted Cranford, San Diego State University

Human technology, meanwhile, has made the ocean a noisy place. The propellers and engines of commercial ships create chronic, low-frequency noise that’s within the hearing range of many marine species, including baleen whales like the minke. The oil and gas industry is a major contributor, not only because of offshore drilling, but due to seismic testing for potential drilling sites, which involves blasting air at the ocean floor and measuring the (loud) sound that comes back. Military sonar operations can also have a profound impact; so much so that several years ago, environmental groups filed lawsuits against the U.S. Navy over its sonar testing off the coasts of California and Hawaii. (The environmentalists won, but the new rules may not be much better.)

Using the CT scans and computer modeling, San Diego State University biologist Ted Cranford predicted the ranges of audible sounds for the fin whale and the minke. To do so, he and his team scanned the body of an 11-foot-long minke whale calf (euthanized after being stranded on a Maryland beach in 2012 and preserved) with a CT scanner built to detect flaws in solid-fuel rocket engines. Cranford and his colleague Peter Krysl had previously used the same technique to scan the heads of a Cuvier’s beaked whale and a sperm whale to generate computer simulations of their auditory systems [PDF].

To save time scanning the minke calf, Cranford and the team ended up cutting the whale in half and scanning both parts. Then they digitally reconstructed it for the purposes of the model.

The scans, which assessed tissue density and elasticity, helped them visualize how sound waves vibrate through the skull and soft tissue of a whale’s head. According to models created with that data, minke whales’ hearing is sensitive to a larger range of sound frequencies than previously thought. The whales are sensitive to higher frequencies beyond those of each other’s vocalizations, leading the researchers to believe that they may be trying to hear the higher-frequency sounds of orcas, one of their main predators. (Toothed whales and dolphins communicate at higher frequencies than baleen whales do.)

Knowing the exact frequencies whales can hear is an important part of figuring out just how much human-created noise pollution affects them. By some estimates, according to Cranford, the low-frequency noise underwater created by human activity has doubled every 10 years for the past half-century. "Understanding how various marine vertebrates receive and process low-frequency sound is crucial for assessing the potential impacts" of that noise, he said in a press statement.

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Scientific Reports, Fernando Ramirez Rozzi
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Stones, Bones, and Wrecks
Humans Might Have Practiced Brain Surgery on Cows 5000 Years Ago
Scientific Reports, Fernando Ramirez Rozzi
Scientific Reports, Fernando Ramirez Rozzi

In the 1970s, archaeologists discovered a site in France containing hundreds of cow skeletons dating back 5000 to 5400 years. The sheer number wasn't surprising—human agriculture in that part of the world was booming by 3000 BCE. What perplexed scientists was something uncovered there a few decades later: a cow skull bearing a thoughtfully drilled hole. Now, a team of researchers has released evidence that suggests the hole is an early example of animal brain surgery.

Fernando Ramírez Rozzi, a paleontologist with the French National Center for Scientific Research, and Alain Froment, an anthropologist at the Museum of Mankind in Paris, published their findings in the journal Nature Scientific Reports. After comparing the opening to the holes chiseled into the skulls of humans from the same era, they found the bones bore some striking similarities. They didn't show any signs of fracturing from blunt force trauma; rather, the hole in the cow skull, like those in the human skulls, seemed to have been carved out carefully using a tool made for exactly that purpose. That suggests that the hole is evidence of the earliest known veterinary surgery performed by humans.

Trepanation, or the practice of boring holes into human skulls, is one of the oldest forms of surgery. Experts are still unsure why ancient humans did this, but the level of care that went into the procedures suggests that the surgery was likely used to treat sick patients while they were still alive. Why a person would perform this same surgery on a cow, however, is harder to explain.

The authors present a few theories, the first being that these ancient brain surgeons were treating a sick cow the same way they might treat a sick human. If a cow was suffering from a neural disease like epilepsy, perhaps they though that cutting a hole in its head would relieve whatever was agitating the brain. The cow would have needed to be pretty special to warrant such an effort when there were hundreds of healthy cows living on the same plot of land, as evidenced by the skeletons it was found with.

Another possible explanation was that whoever operated on the cow did so as practice to prepare them for drilling into the heads of live humans one day. "Cranial surgery requires great manual dexterity and a complete knowledge of the anatomy of the brain and vessel distribution," the authors write in the study. "It is possible that the mastery of techniques in cranial surgery shown in the Mesolithic and Neolithic periods was acquired through experimentation on animals."

Either way, the bovine patient didn't live to see the results of the procedure: The bone around the hole hadn't healed at all, which suggests the cow either died during surgery or wasn't alive to begin with.

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