The Rare and Not-So-Rare Fascinating World of the Chimera

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When you think of the word Chimera, you might think of the mythological beast. In Greek myths, the Chimera was a female fire-breathing monster with three different animal appearances. 

A Strange Mythological Beast

From the front, a Chimera had a lion’s appearance. However, the middle was that of a goat. At the back end, the Chimera resembled a dragon. Nevertheless, artistic representations are widely different. Sometimes, the lion has a bizarre goat’s head in the middle of its back with the tail of a snake.

Today, Chimera can describe any imaginary beast seen in architecture. More broadly, the word conjures a fanciful illusion, fabrication, or unrealizable dream, according to Merriam-Webster.

Real-Life Chimeras

Apart from the mythological beasts, Chimeras are also very real. In fact, it’s possible that many people are Chimeras, to some degree. Also, it’s known that many mammal species are a type of Chimera due to the ancient process of childbirth. 

What does that mean?

A Chimera describes a person or animal with two different sets of DNA in their bodies. Sometimes, the DNA is from the same species, but today, Chimeras can also feature genes from different species.

Artificially Created Chimeras

How does this happen? Chimeras occur naturally but can also happen as a result of genetic tinkering. (Hence, the possibility of more than one species.)

Today, due to advances in DNA gene editing, scientists can create Chimeras in the lab. Firstly, in 2015, Chinese scientists first edited human embryos’ DNA using a gene-editing technique. By 2018, a Chinese scientist announced Chinese girls named Lulu and Nana had been successfully born with edited genes.

Then, in 2019, China created Human-Monkey Chimera embryos to grow human organs.

Ethically, creating Chimeras in a lab is, of course, extremely controversial. The practice, along with CRISPR gene-editing in human embryos, sparked a global outcry from scientists. It remains illegal in most parts of the world.

More recently, the researchers who developed the CRISPR tool won the Nobel Prize. The technique has transformed responsible genetic science, but an international team concluded it wasn’t mature enough to alter human embryos. Nevertheless, it’s already happened.

See more from ABC News Australia below:

Naturally Occurring Chimeras

Historically, most Chimeras occurred naturally. For example, a woman pregnant with fraternal twins can give birth to a Chimera. 

If one embryo dies in the womb, it can be absorbed by its twin. Thus, a baby is born with two sets of DNA. Most of the time, the person won’t ever know they are a Chimera. The New York Times dubbed it a “pregnancy souvenir.”

Also, a pregnant mother can become a Microchimera when she absorbs cells from a fetus that migrate into the blood and organs. Interestingly, this type of Chimera could be “very common, if not universal,” according to experts. 

In addition, there have been studies that show Microchimeras are common. Unfortunately, mothers lose twins at a relatively high rate, as much as 21 to 30% of the time. It’s referred to as the “Vanishing Twin Syndrome.” In such cases, it’s possible the mother may absorb the cells.

Researchers can detect Microchimeras by finding mothers who have a Y chromosome found only in males. In such cases, they know for sure that the cells came from a male fetus. 

Interestingly, the cells can live inside the mother for a lifetime. In one case, a woman who lived to 94 years old was found to have DNA traces from her male fetus inside her brain. Scientists are just beginning to research how these cells could influence behavior.

Rare Documented Human Chimeras

Cases in which a person is a documented Chimera remain exceedingly rare, with as few as 30 documented cases worldwide. 

In one case, a mother named Lydia Fairchild almost lost custody of her children when Social Services discovered her children didn’t share her DNA. Then, she was accused of abducting the children!

After many accusations, a court officer witnessed her giving birth to another child, immediately testing the baby. Even so, the test showed the child wasn’t hers, and officials still suspected she was a surrogate.

Finally, a similar case from Boston tipped off her attorney that she could be a Chimera. Following testing, Fairchild was found to be her own twin and not an imposter.

See more from Facts Verse below:

Organ and Tissue Transplant Chimeras

When a person receives tissue or organs from a donor, that can technically result in a Chimera. A donor’s bone marrow retains the donor’s DNA. Sometimes, the recipient has 100% donor DNA in their blood cells. In this case, it’s called “complete chimerism.”

In other cases, there’s a case of “mixed chimerism,” with DNA from donor and recipient mixed.

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Rare Half-Male, Half-Female Chimeras

In nature, sometimes, a Chimera can exhibit the genetic traits of both males and females. Recently, one such specimen was found in Pennsylvania. There, a beautiful songbird called a grossbeak was found exhibiting male coloration on the right and female on the left. In 60 years of bird collection, only five cases have been recorded.

Amazingly, the grossbeak was perfectly split down the middle as male and female. Consequently, it’s a case of bilateral gynandromorphism, a type of genetic chimerism. 

In the 1920s, a case of bilateral gynandromorphism was described in a chicken, which laid eggs. Early in the bird’s development as a zygote, two ova fuse, bonding two fraternal twins.

The condition has been found in lobsters, crabs, shrimp, ants, butterflies, moths, spiders, and bees. However, it’s exceedingly rare. In humans, it’s thought that hormones that determine sex rule out cases of bilateral gynandromorphism.

The researcher who captured the bird alive said finding the bird was like “seeing a unicorn,” a “once-in-a-lifetime discovery.” The rare bird’s discovery delighted the biologists who found the bird as part of a routine banding program. Afterward, the researchers released it back into the wild.

See the bird below in the video from LiveScience:

A Chimera Cardinal

Last year, another male/female songbird was spotted in Erie, Pennsylvania. This time, it was a northern cardinal. In appearance, it had the female colors on the left and the red male colors on the right.

A homeowner who set up a bird feeder described how the bird behaved, singing with a male companion in courtship behavior.

“It does seem to be traveling with a male. Every time we have seen this bird, there is a male cardinal as a companion. They always fly in and out of our yard together,” Caldwell told Forbes.

Although both a male and female, the Cardinal may be able to produce eggs. On the left side, it could have one functional ovary.

See the Chimera Cardinal from Nat Geo WILD below:


Featured Image: Screenshots via YouTube