DNA – Page 3 – Pain In The Bud

Cat Domestication Was The Start Of A Beautiful Friendship

Domestication’s real goal: to make cats cuddly as well as great mousers.

Cats have been doing things their way since the very beginning.

Unlike literally every other domesticated animal, cats were not domesticated by humans. They did it to themselves.

As if that didn’t make them unique enough, they lay claim to another major distinction: they’re the only species of obligate carnivores to undergo domestication in the entire history of human existence.

That explains why cats, more than any other animal that depends on humans, so closely resemble the wild animals they were before signing up for the good life of naps, warmth, endless rodents to hunt and free food from their new human friends.

In a new essay for The Conversation, evolutionary biologist Jonathan Losos, author of The Age of Cats: From the Savanna to Your Sofa, notes new DNA analysis settles the question of where cats came from once and for all.

Domestic cats are descended from North African wildcats, specifically the species felis sylvestris lybica. Unlike dogs, who underwent telltale physical transformations when they evolved from wolves, house cats “appear basically indistinguishable from wildcats.”

“In fact,” Losos writes, “only 13 genes have been changed by natural selection during the domestication process. By contrast, almost three times as many genes changed during the descent of dogs from wolves.”

While the change in genetics that happen with domestication left cats pretty much as they were physically, the process made dramatic changes in the feline brain, reducing regions governing fear and expanding those related to social behavior. The result? The major difference between house cats and their wildcat ancestors is disposition.

In other words, domestication made cats cuddly.

Notably, felis sylvestris lybica had to be pretty friendly in the first place, as well as bold and driven by the now-legendary feline curiosity to risk padding into human settlements with their bright lights, strange smells, open flames and the two-legged giants striding around them.

They didn’t have a way of negotiating or signaling their intent. They couldn’t say: “Hey guys, we’re here to kill and eat the tasty rodents who have been giving you problems by chowing down on your yums, but we don’t want your yums for ourselves. Plants are disgusting!”

So they had to demonstrate their usefulness, prove their worth, and enjoy the fruits of it by curling up in front of warm fires or on human laps.

That explains why it was the African wildcat that became a human companion species and not European wildcats, whom Losos notes are often “hellaciously mean” in interactions with people, even if they’re raised around humans when they’re young. It was also a matter of being in the right place at the right time, as nascent human civilization took root in the Fertile Crescent.

But ultimately, just like cats decided to domesticate themselves and didn’t really bother to consult us about it, so too do they bend us to their will with an entire repertoire of manipulative behavior, from solicitation purrs to incessant meowing and having a talent for looking their cutest when they want something.

While we may think we set the rules and parameters of our relationship with the furry little ones, as Losos notes, “cats usually train us more than we train them.”

Read the whole thing here:

Feline evolution: How house cats and humans domesticated each other

Another Study Finds Cat Hair Can Place Suspects At Crime Scenes

Through a new resequencing technique, forensics can yield more information from a single cat hair than ever before, with major implications for crimes in places where felines are present.

Last year a forensic study broke new ground by proving there’s usable human DNA in cat fur which can prove a person was in a home or interacted with a particular pet.

Now a new study looked at the opposite situation, establishing that a single cat hair on a person’s clothes can tie them back to an individual cat — and the scene of a crime.

The general public, criminals included, are more aware of DNA and forensic techniques than they’ve ever been thanks to ubiquitous police procedurals, some of which focus heavily on the investigation and evidence-gathering aspect of police work.

But even the most fastidious criminal who is careful not to leave a single print or strand of his own hair at a crime scene can be undone by cat fur clinging to clothes. In fact it’s almost impossible for a person to spend more than a few minutes inside a cat-occupied home without picking up at least some fur, the research team said.

Detective Buddy — “Detective Inspector Buddy, at your service. Now tell me about the missing turkey…” Credit: Pain In The Bud

The paper, published this month in Forensic Science International: Genetics, outlines a new method for sequencing genetic information found on strands of cat fur.

“Hair shed by your cat lacks the hair root, so it contains very little useable DNA,” said Emily Patterson, the paper’s lead author.

Previously it wasn’t possible to narrow down with certainty whether a strand of hair belonged to a particular cat, but the research team found a new way to resequence DNA in a way that can link it to individual felines. The team’s new method doesn’t require any additional hair or roots, solving the original problem.

To prove their method works, they extracted fur from the body of a deceased cat and were able to match it to her surviving brother.

“In criminal cases where there is no human DNA available to test, pet hair is a valuable source of linking evidence, and our method makes it much more powerful,” said Mark Jobling, a geneticist at the University of Jobling and co-author of the new study. “The same approach could also be applied to other species — in particular, dogs.”

While dog hair can potentially be used in the same way, cat hair may have more forensic value from a prosecurorial standpoint because cats are territorial and many don’t leave their homes. It’s much easier to prove a suspect was inside a home if he or she is linked to an indoor-only cat than if the suspect’s clothes have fur from a dog who is walked around the neighborhood a few times a day.

Cats May Be Able To Help Detectives Solve Crimes

An Australian team decided to look for DNA evidence in a novel place: cat fur. Their findings could give law enforcement a powerful new tool to identify crime suspects.

Check out our newest feature, catwire!

When you think of a crime scene, you probably picture uniformed officers manning the perimeter, crime scene tape cordoning off the room where the deed was done, detectives trying to reconstruct what happened, and techs collecting evidence.

Those techs might swab surfaces for traces of a suspect. Drinking cups and water bottles might be dusted for fingerprints, stray hair might be bagged and sent back to the laboratory for analysis. Discarded cigarette butts, door handles, buzzers — they can all yield evidence, to say nothing of cell phones, USB sticks and smart appliances.

But what about the pets? If a suspect was especially careful not to leave prints or touch anything at the crime scene, could the fur of a cat harbor DNA?

A team comprised of scientists from Australia’s College of Science and Engineering at Flinders and the Victoria Police Forensic Services Department wanted to know if cat fur could indeed hold critical evidence at crime scenes, so they conducted a study involving 20 pet cats from different homes, and what they found could provide an important tool for law enforcement. Their findings were published in the journal Forensic Science International.

If detectives are trying to piece together the identities of robbers who, say, broke into a home, brutalized the people there at gunpoint and stole their valuables, they can’t interview the victims’ pet cats about what they saw, but it turns out they can swab the kitties’ fur and have an excellent chance of retrieving useful DNA.

Blacksad is a famous feline detective in his own series of comic books. He may have to be careful not to leave his stray fur all over his own crime scenes.

The research team swabbed the fur of pet cats in their test households, took DNA samples of the adults living in those homes — who were the stand-ins for victims — and asked the human participants to fill out surveys asking about their cats, what they do on a typical day, and whether or not they have interaction with people outside the home.

After the team conducted DNA analysis on the fur swabs “[d]etectable levels of DNA were found in 80% of the samples and interpretable profiles that could be linked to a person of interest were generated in 70% of the cats tested,” the study authors wrote.

While most of the samples matched the DNA of people who lived in the homes — as expected — samples from six cats revealed the presence of DNA from other people. The research team didn’t take DNA samples of minors, and two of the positive fur swab samples came from cats who lived in a home with a child and slept in that child’s bed most evenings. But four other samples turned up “mystery” DNA even though no one else had visited those homes for at least several days.

For DNA from pets to have any real evidentiary value, prosecutors have to prove a “chain of custody” of sorts, establishing that suspects could not have had contact with the animals in question unless they were inside a home where a crime has taken place. If the cat is allowed to roam outdoors every day, for example, it becomes much more difficult to prove a suspect’s DNA was transferred to a pet inside a home rather than on the street.

That’s why the research team is hopeful, but also cautions that their study is a first step toward understanding more about how human DNA is transferred to fur, whether it requires a person to be physically present (as opposed to their DNA being passed along secondhand in stray hair or skin cells), how long a cat’s fur can harbor human DNA, and other questions prosecutors will have to answer.

“This type of data can help us understand the meaning of the DNA results obtained, especially if there is a match to a person of interest,” said study co-author Mariya Goray, a DNA transfer expert. “Are these DNA finding a result of a criminal activity or could they have been transferred and deposited at the scene via a pet?”

The team recommends more research “on the transfer, persistence and prevalence of human DNA to and from cats and other pet animals and the influences animal behavioral habits, the DNA shedder status of the owners and many other relevant factors.”

If they do answer the aforementioned questions and prosecutors believe they can establish a suspect’s presence at a crime scene thanks to feline-provided evidence, it might not be too long before we see a cat-centric episode on future seasons of Law & Order or CSI, both of which are scheduled to be revived as police procedurals enjoy a resurgence on TV.