Screenshot, TwinzyOKC
Screenshot, TwinzyOKC

What is Chimerism?

Screenshot, TwinzyOKC
Screenshot, TwinzyOKC

Conception is normally a pretty straightforward process: One lucky sperm wiggles its way into one lucky egg. In the case of fraternal twins, each sperm-and-egg pair is just one half of a double date. The resulting fertilized eggs trundle along and begin dividing separately, eventually becoming two separate fetuses. But sometimes, one egg engulfs the other, effectively “eating” its twin.

This isn't as messy as it sounds. At that stage in development, we’re all just smooshy single cells. The newly fattened twin-eating cell goes about its business, dividing and dividing, growing and growing, until, many months later, it becomes a person (or a lion, or a rabbit, or a weasel, depending on its parents).

The scientific term is tetragametic chimerism, although the origin of that word is hardly scientific. The ancient Greek Chimera was a mythical monster with the body and fire-breathing head of a lion, a goat head rising from its back, and a snake tail. Over time, the word chimera came to mean any kind of combo-pack animal—including, eventually, people with two sets of DNA.

Because, young as those twin cells are when they become one, each cell has its own set of DNA. After the Big Meal, both sets come to reside in a single cell, which eventually becomes a single animal.

People (and animals) with chimerism may be visibly different. They may have one brown eye and one blue, or one hitchhiker’s thumb and one straight one. Their skin may, almost imperceptibly, be a swirl of two different colors. Chimeric animals can sport a two-tone pattern split right down the middle. That appears to be the case for Twinzy, pictured above checking out his reflection in a mirror, a budgie who lives at Rudy's Pet Supply & Feed in Oklahoma City. 

Most of the time, though, chimeras look just like everybody else. That was the case for Lydia Fairchild. As a pregnant, single mother of two applying for welfare benefits, in 2002 Fairchild and her children had to undergo paternity testing. The results confirmed that the father of Fairchild’s children was, in fact, their father. But, according to the DNA tests, Fairchild wasn't their mother.

The state threatened to take her children away. Fairchild was accused of welfare fraud and illegal surrogacy. The DNA evidence against her seemed airtight, and even her own parents began to doubt her story.

Then her lawyer saw a story in the New England Journal of Medicine that seemed startlingly familiar. A woman named Karen Keegan had been in need of a kidney transplant. To identify a possible donor, Keegan and her family members had their DNA tested. The results came back: Keegan could not be the mother of two of her three sons.

Eventually, researchers at the National Institutes of Health began testing DNA from different parts of Keegan’s body. The pieces fell into place: Keegan was a chimera. After the researchers published their findings, Lydia Fairchild’s lawyer took their findings to the judge, who granted Fairchild official custody of her own children. After the case was dismissed, scientists determined that Fairchild did, indeed, have two sets of DNA.

So it turns out chimerism isn’t all fun and games (and twin-eating). The genetic, physical, and social consequences may be nonexistent. They could be super-cool and make you look like a badass. Or they could be life changing.

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A Baby's Cries Might Hint at What the Child Will Sound Like as an Adult
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Babies may be incapable of talking, but at just a few months old, they've already developed many of the characteristics that will one day make their speaking voice distinct. That's the takeaway from a new study, reported by The New York Times, in which a team of bioacoustic researchers found that you can tell what infants will sound like at age 5 by analyzing their cries.

For their study, published in the journal Biology Letters [PDF], the researchers recorded the voices of 15 French children 4 to 5 years old. They then compared the clips to the children's "mild discomfort cries" recorded when they were 2 to 5 months old. The results showed that a baby's voice can be used to predict 41 percent of the variances they will have in their vocal pitch at age 5.

Other studies have suggested that what our voices sound like when we're young is a strong indicator of what they will sound like later on—even after puberty changes our vocal chords. A boy's voice pitch at age 7 can predict up to 64 percent of the distinguishing features his voice will have as an adult.

The study authors write that many of these variances may develop before childhood, and potentially in utero: "These observations suggest that inter-individual differences in [voice pitch] arise early in life and are largely unaffected by puberty, and raise the possibility that [pitch] may even be determined before birth."

The most important markers that determine pitch are the length, size, and tension of our vocal folds. But those aren't the only determinants: Environmental factors like smoking, pollution, and climate can affect how our voices sound as well, though these changes are usually temporary.

[h/t The New York Times]

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10 Science-Backed Tips for Getting a Cat to Like You
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Like so many other humans, you might find cats to be mysterious creatures. But believe it or not, it’s not that hard to make friends with a feline, if you know what to do. Here are some tips on how to effectively buddy up with a kitty, drawn from scientific studies and my own experience as a researcher and cat behavioral consultant.

1. LET THE CAT CALL THE SHOTS.

When we see cats, we really want to pet them—but according to two Swiss studies, the best approach is to let kitty make the first move.

Research done in 51 Swiss homes with cats has shown that when humans sit back and wait—and focus on something else, like a good book—a cat is more likely to approach, and less likely to withdraw when people respond. (This preference explains why so many kitties are attracted to people with allergies—because allergic people are usually trying to not pet them.) Another study found that interactions last longer and are more positive when the kitty both initiates the activity and decides when it ends. Play a little hard to get, and you might find that they can’t get enough of you.

2. APPROACH A CAT THE WAY THEY GREET EACH OTHER (SORT OF).

person extending finger to cat's nose
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Felines who are friendly with each other greet each other nose to nose. You can mimic that behavior by offering a non-threatening finger tip at their nose level, a few inches away. Don’t hover, just bend down and gently extend your hand. Many cats will walk up and sniff your finger, and may even rub into it. Now that's a successful greeting.

3. PET CATS WHERE THEY LIKE IT MOST …

They're very sensitive to touch, and generally, they tend to like being petted in some places more than others. A small 2002 study demonstrated that cats showed more positive responses—like purring, blinking, and kneading their paws—to petting on the forehead area and the cheeks. They were more likely to react negatively—by hissing, swatting, or swishing their tails—when petted in the tail area. A more recent study validated these findings with a larger sample size—and many owners can testify to these preferences.

Of course, every animal is an individual, but these studies give us a good starting point, especially if you're meeting a cat for the first time.

4. … AND IF YOU GET NEGATIVE FEEDBACK, GIVE THE CAT SOME SPACE.

There are plenty of signs that a cat doesn't like your actions. These can range from the overt—such as hissing and biting—to the more subtle: flattening their ears, looking at your hand, or twitching their tails. When you get one of those signals, it’s time to back off.

Many of the owners I work with to correct behavioral issues don't retreat when they should, partially because they enjoy the experience of petting their cat so much that they fail to recognize that kitty isn’t enjoying it too. You can’t force a feline to like being handled (this is especially true of feral cats), but when they learn that you’ll respect their terms, the more likely they will be to trust you—and come back for more attention when they're ready.

5. DON’T OVERFEED YOUR CAT.

Many think that food equals love, and that withholding food might make your kitty hate you, but a recent study of obese felines from Cornell University showed the opposite is true—at least for a period of time. About a month after 58 overweight kitties were placed on a diet, three-quarters of their owners reported that their dieting felines were more affectionate, purred more often, and were more likely to sit in their owner's lap. This adorable behavior came with some not-so-cute side effects—the cats also begged and meowed more—but by week eight, both the good and bad behavior had abated for about half the animals.

Regardless of whether a diet makes your pet cuddlier, keeping your pet on the slender side is a great way to help them stay healthy and ward off problems like diabetes, joint pain, and uncleanliness. (Overweight animals have difficulty grooming themselves—and do you really want them sitting on your lap if they can’t keep their butt clean?)

6. PLAY WITH THEM—A LOT.

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Most of the behavior problems that I've witnessed stem from boredom and a lack of routine playtime. No one thinks twice about walking their dog every day, but many people fail to recognize that felines are stealth predators who need a regular outlet for that energy. A recent study suggested that cats prefer human interaction over food, but a closer look at the data demonstrated that what really attracted them to humans was the presence of an interactive toy. One of their top choices is a wand-style toy with feathers, strings, or other prey-like attachments that evoke predatory behavior. Daily interactive play is a great way to bond with them when they’re not in the mood to cuddle—and to keep them fit. Try the Go-Cat Da Bird or any of Neko Flies interchangeable cat toys.  

7. KEEP YOUR CAT INDOORS.

A study conducted in Italy showed that felines who stayed mostly indoors (they had one hour of supervised access to a small garden each day) were more “in sync” with their owners than felines who were allowed free access to the outdoors. The indoor kitties were more active during the day, when their owners were likely to be active, and less active at night, when humans like to sleep. (Many people believe cats are nocturnal, but they are naturally crepuscular—active at dawn and dusk.)

8. SOCIALIZE CATS WHEN THEY'RE YOUNG.

Multiple studies have shown that just a few minutes a day of positive handling by humans helps kittens grow up to be friendlier and more trusting of humans. The ideal age to socialize kittens is when they're between 2 and 9 weeks old. One 2008 study found that shelter kittens that had been given a lot of "enhanced socialization"—additional attention, affection, and play—were, a year later, more affectionate with their owners and less fearful than other kittens adopted from the same shelters.

You can help socialize kittens by volunteering as a foster caretaker. Fostering ensures they get plenty of interaction with people, which will help them will be comfortable around potential adopters. You'll also be doing your local shelter a huge favor by alleviating overcrowding.

9. TAKE THE CAT'S PERSONALITY—AND YOUR OWN—INTO CONSIDERATION WHEN ADOPTING.

If you want to adopt an older animal, take some time at the shelter to get to know them first, since adopters of adult cats report that personality played a big role in their decision to take an animal home permanently and had an impact on their satisfaction with their new companion. Better yet, foster one first. Shelters can be stressful, so you'll get a better sense of what an animal is really like when they're in your home. Not all cats are socialized well when they're young, so a cat may have their own unique rules about what kinds of interactions they're okay with.

It's also key to remember that a cat's appearance isn't indicative of their personality—and it's not just black cats who get a bad rap. In 2012, I published a study with 189 participants that showed that people were likely to assign personality traits to felines based solely on their fur color. Among other things, they tended to think orange cats would be the nicest and white cats the most aloof. (Needless to say, these are inaccurate assumptions.) And it's not just the kitty's personality that matters—yours is important too. Another study I conducted in 2014 of nearly 1100 pet owners suggested that self-identified “cat people” tend to be more introverted and anxious when compared to dog people. (We’re also more prone to being open-minded and creative, so it’s not all bad.) If you’re outgoing and active, a more playful feline could be for you. If you prefer nights spent snuggling on the couch, a mellow, shy-but-sweet lovebug could be your perfect pet.

10. BE A KEEN OBSERVER OF THEIR BEHAVIOR.

Overall, use your common sense. Be a diligent and objective observer of how they respond to your actions. Feline body language can be subtle—something as small as an eye-blink can indicate contentment, while ear twitches might signal irritation—but as you learn their cues, you'll find yourself much more in tune with how they're feeling. And if you adjust your behaviors accordingly, you'll find soon enough that you've earned a cat's trust.

Mikel Delgado received her Ph.D. at UC-Berkeley in psychology studying animal behavior and human-pet relationships. She's a researcher at the UC Davis School of Veterinary Medicine and co-founder of the cat behavior consulting company Feline Minds.

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