In 2005, an impossibly mysterious law enforcement case happened in Alaska. A man was in prison for a crime. During that time, a sexual assault occurred elsewhere in the state. The evidence in the assault case was unassailable: Alaska investigators uploaded a DNA profile from semen to a DNA database and found a match to the inmate’s DNA. That incriminating evidence was found on the body and clothing of the victim immediately after the crime. DNA does not lie. The great mystery is, how did that felon escape from jail to commit sexual assault, only to return quickly behind bars quickly and undetected? It was confounding.
The mystery was that there was a chimera involved, one totally unknown to the inmate, the victim, and the police. A little explanation is in order. Chimerism is associated with Greek mythology, where a chimera is a fire-breathing monster with the head of a lion, body of a goat, and tail of a snake—a fantastic blending of different animals into one, often a monstrous fire-breathing creature composed of the parts of multiple animals. Chimeras appeared several thousand years ago in the form of statuary, mosaics, painting, and literature. This “frightful monster” appeared in the famous Greek tale of Oedipus, an unfortunate fellow who was accursed with the fate of murdering his father and marrying his mother. The Sphinx–outsmarted by Oedipus—killed herself and thus Oedipus rescued the city of Thebes.
“The country around was beset by a frightful monster, the Sphinx, a creature shaped like a winged lion, but with the breast and face of a woman. She lay in wait for the wayfarers along the roads to the city and whomever she seized she put a riddle to, telling him if he could answer it, she would let him go. No one could, and the horrible creature devoured man after man until the city was in a state of siege.”
-Edith Hamilton, Mythology
Chimeras exist in contemporary works of fantasy and science fiction, but I will not go there. The real world is mysterious enough without that complication. The Oedipus narrative stands out because the monster here did not possess merely the savageness of beast, but also had the intelligence of man–a fearful and deadly combination through the ages.
Normally–in humans and other animals–the animal has cells with only its unique DNA, which is a basic tenet of genetics, understood by anyone with even rudimentary acquaintance with biology, genetics, evolution, and forensics (or has a TV). The body has numerous types of cells, but all the cells contain your exact type of DNA. Right?
But with a chimera, this basic understanding is now obsolete, at least more complicated. A chimera will have two sets of cells with two distinct types of DNA. In fact, chimeras appear in nature, albeit probably infrequently and often overlooked. A chimera is a person or animal with cells from two or more different sources, resulting in two or more sets of DNA. There are several causes for the appearance of such chimeras. Until fairly recently, the rules of DNA were such that the idea of a chimera was more than mysterious; it was impossible.
With a little digging, it is possible to find that chimeras exist in the animal world and have been around for along time. It turns out that meat-eating mammals have a tangled taxonomic history. Tens of millions of years ago, it would have been impossible to discern which species were fated to evolve into dogs, big cats, or even bears and weasels. Amphicyon, the bear dog did, in fact, look like a smallish bear with the head of a dog. However, it was technically a creodont, a family of carnivores only distantly related to modern canines and ursines. True to its name, the bear dog ate pretty much anything it could get its paws on. This 200-pound beast may have been capable of swatting prey senseless with a single swipe of its well-muscled forearms.
The Horse Dragon has nothing to do with the popular Game of Thrones. Hippodraco, the horse dragon, did not really look much like a dragon, and it certainly did not look anything like a horse. Apparently, this newly-discovered dinosaur received its name because it was much smaller than others of its breed, only about the size of a small horse in comparison to the 2 and 3 ton ornithopods like Iguanodon, which Hippodraco vaguely resembled. It may be that its “type fossil”
may be a juvenile, which in Hippodraco adulthood might have achieved Iguanodon-like sizes.
The Man Bird, Anthropornis, was indirectly referenced by a horror writer. That reference is vague in the extreme. It is hard to imagine the actual cuddly-looking prehistoric penguin being something of a T. rex of the penguin evolutionary world. Anthropornis was \six feet tall and weighed ~200 pounds, which was bigger on average than the putative Giant Penguin, Icadyptes.
As imposing as it was, the man bird was far from the biggest avian chimera; that distinction should be awarded to the 900-pound Elephant Bird of Pleistocene Madagascar.
The Rat Croc Araripesuchus, received its name because that prehistoric crocodile only weighed about 200 pounds and had a rat-like head. There is also Kaprosuchus, the boar croc with oversized tusks in its upper and lower jaws, and Anatosuchus, the duck croc possessing a flat, vaguely ducklike snout used to sift through the underbrush for food. Science is not all dull and boring: paleontologist Paul Sereno found he could generate headlines with his slightly off-kilter nomenclature.
The Fish Lizard Ichthyosaurus, looked almost exactly like a giant bluefin tuna, with the exception that it was actually a marine reptile of the early Jurassic period. In fact, Ichthyosaurus was just one of a wide variety of “fish lizards” bearing less chimeric names like Cymbospondylus—“oat-shaped vertebrae”—and Temnodontosaurus—”cutting-toothed lizard”.
On the other hand there is also the Lizard Fish. Ichthyosaurus–the fish lizard–had been in the reference books for decades when a mischievous scientist bestowed the name Saurichthys (lizard fish) on a newly discovered species of ray-finned fish. Beyond the confusing nomenclaturel it is not clear what the “lizard” part of this fish’s name was intended to reference since Saurichthys looked like a modern sturgeon or barracuda.
The Marsupial Lion, Thylacoleo, looks like a tiger with the head of a kangaroo or a giant wombat with the head of a jaguar. It is evolution, not some sort of trick by nature. The process of convergent evolution ensures that animals inhabiting similar ecosystems develop similar body plans, with the result that Thylacoleo was an Australian marsupial that was virtually indistinguishable from a big cat. Another example was the even bigger Thylacosmilus of South Africa, which looked like a saber-toothed tiger. Both looks were evolutionarily useful for getting meat for meals.
The Ostrich Lizard Struthiosaurus, was initially deemed to be a bird-like dinosaur by a 19th-century paleontologist. In fact, he had discovered an extremely petite ankylosaur, which had about as much in common with modern ostriches as orangutans do with baseball.
A chimera in name only, Ichthyornis, the Fish Bird, was named partly in reference to its vaguely fish-like vertebrae, and partly in reference to its heavily fish diet. This late Cretaceous bird looked very much like a seagull and probably flocked along the shores of the Western Interior Sea. More importantly from an evolutionary historical perspective, Icthyornis was the first prehistoric bird known to have teeth and must have been a startling sight to the professor who unearthed in Kansas in 1870.
Back to Alaska and 2004 and the man in prison at the time whose DNA plainly said that he was the perpetrator of a sexual assault. Alaska has excellent investigators. The sexual assault victim insisted that there had been one attacker, but DNA pointed to two suspects—a potential conundrum. They discovered that the inmate had received a bone marrow transplant from his brother years earlier. The astute investigators uploaded a DNA profile extracted from semen to a criminal DNA database of the brother’s blood, who was eventually convicted in the case. The Impossible Crime that posed the question, was DNA wrong. The answer is simple: no.
After speaking to friends and family members, they found out that the man in jail had received a bone marrow transplant from his brother, who was not in jail. When the guilty brother donated his marrow, blood cells bearing his DNA spread in his sibling’s bloodstream, thus changing the two brothers were now identical twins—in terms of blood, at least. The simple swab of the cheeks of the man in prison, confirmed that his brother had committed the crime the fact that he physically could not have committed the crime—that exonerated him. It also answered the conundrum of, had DNA gone mad? And could DNA actually lie?
DNA does not lie, but it has its eccentricities. A genius in Nevada came upon a brilliant idea for an experiment when her colleague had to receive a bone marrow transplant. Chris Long is an information technology employee with the Washoe County sheriff’s department in Reno. He developed acute myeloid leukemia and needed a bone marrow transplant to survive. A donor was found in Germany. When Chris told his colleagues about the impending transplant, one of them–Renee Romero–suspected that Chris’s blood DNA might change, given that the goal was to replace diseased blood with healthy blood, which would include the DNA it contains. She saw a unique opportunity to investigate and to set up an important human subject experiment.
She told Chris, “We need to swab the heck out of you before you have this procedure to see how this DNA takes over your body.”
Chris agreed. Tests before and after the transplant revealed new DNA in his blood, semen, lip, and cheek, swabs. Chris Long had been changed into a chimera [having two distinct sets of DNA] four months after his transplant, which cured him of cancer. Only the DNA in his chest and head was still Chris’s own.
The crime lab experiment persisted, and—after four years–the researchers found that the DNA in Long’s semen had been completely replaced by his donor’s–a German man with whom he had exchanged just a handful of messages. It was the goal of the procedure: weak blood is replaced by healthy blood, and with it, the DNA it contains.
“We were shocked that Chris was no longer present at all,” criminal investigator Darby Stienmetz said.
Colleague Brittney Chilton pointed out that if another patient who responded similarly to a transplant went on to commit a crime, it could mislead investigators. It has already confounded investigators in at least two cases. Chimerism can occur in humans during pregnancy when fetal cells migrate outside the uterus and into the mother’s bloodstream.
Two high-profile cases of chimerism in the United States were discovered in 1998. A fifty-two year-old woman named Karen Keegan was in renal failure and needed a kidney transplant. She sought help from Beth Israel Deaconess Hospital in Boston. Her doctor suggested that Mrs. Keegan and her immediate family undergo compatibility testing in order to find a kidney donor. The doctor conduced histocompatability testing to compare any potential donor’s HLAs [ human leukocyte antigen “tissue typing”] to Mrs. Keegan, the intended recipient.
The family’s histocompatibility results indicated that she was not the biological mother of two of her three children—the two eldest sons–which was news to her, since she had gone through the entire natural process from impregnation, the pregnancy, the delivery, and caring for the three children she loved. Comparison to her two eldest sons showed that she had no genetic similarities to them at all. The researchers had not tested Mrs. Keegan’s third son because he was a child at the time and would be unable to donate a kidney.
The mystery was solved after the research team received a grant from the National Institutes of Health to study Mrs. Keegan and her family further and found that Keegan had evidence of two distinct sets of DNA throughout her body—that Keegan was a chimera—a tetragametic chimera–she had a different set of DNA in her blood cells compared to the other tissues in her body. The doctors who worked with Keegan were familiar with the concept of chimerism and suggested that Keegan undergo further testing. Testing of her brothers and husband proved that her sons were related to them. Subsequent sampling of her skin and hair proved to be futile, but eventually matching DNA was found in her thyroid gland.
In Mrs. Keegan’s case, her two different sets of DNA were found in cells throughout her body. But in other chimeras, there is a dominant set of DNA in the body, with the other set only present in certain tissues.
The second case—that of Lydia Fairchild—came from a legal challenge. After separating from her children’s father, Ms. Fairchild applied for state assistance, a process that required both paternity and maternity tests. As part of the application, both she and Jamie Townsend, her then-estranged partner and her children’s father, had to submit DNA samples in the forms of cheek swabs to establish the maternity and paternity results for the children.
A social worker called Lydia to come to her office after obtaining the maternity test results. During that visit, the social worker and a legal representative confronted Fairchild with DNA evidence that her children were not biologically related to her. Furthermore, they said she was committing welfare fraud by lying about her relationship with her children. DNA analysis found no match between her and her children’s DNA, although there was a clear match between the children and their father, Jamie Townsend. The state of Washington prosecutor’s office took Ms. Fairchild’s case on suspicion that she was committing welfare fraud.
The prosecutor’s office ordered that the family undergo three separate cheek swab DNA tests to account for possible lab error. Each time, the results indicated that Fairchild was not the biological mother of the two children. Although she was able to produce photographs of her with her children throughout their lives, the prosecutor’s office continued to allege that she was not being truthful about the origin of her pregnancies, and that because she had claimed her children as dependents on her application for benefits, doing so constituted welfare fraud. A case of welfare fraud ensued because the prosecutors believed the DNA results to be irrefutable. The prosecutor’s office threatened her with a lie detector test, and Ms. Fairchild agreed undergo the test if it meant proving her children were hers.
Becoming more convinced of the fraud issue, the prosecutor’s office changed its concern to the welfare of the children. Rather than sending Fairchild for a lie detector test, though, they sent her a court summons to determine her relationship with her children. The reasoning flowed from the fact that US courts at the time accepted DNA evidence as infallible; and it was seldom contested in a court of law. Ms. Fairchild could not find a defense attorney as a result, and she was left with the only alternative—to represent herself. When Fairchild went to court, she brought photos from her two previous pregnancies and pictures of her with her children as infants. The court suggested placing her two children in separate foster homes while the case was contested to monitor the children’s wellbeing, since officials assumed that Fairchild was being fraudulent about her relationship with the children. The stakes could not have been higher, and the problem was that everyone was dealing with a situation that appeared to be ultimately mysterious.
Other forms of evidence of Fairchild’s maternity–including photographs of Fairchild with her children throughout their lives, Townsend stating he had witnessed both children’s births, and footprint records taken from the children as neonates, were repeatedly dismissed. Presumably, they were either faked or simply irrelevant. Ms. Fairchild could not even convince a lawyer to represent her because they told her they would not win a case against DNA evidence. She found herself caught between a rock and a hard place.
Even the testimony of Dr. Leonard Dreisbach, the obstetrician who had helped Fairchild give birth, did little to persuade the court in Ms. Fairchild’s favor. The judge–perplexed by seemingly conflicting evidence–ordered that the third child, when born, to be tested as well. He then ordered a court officer to be present at the birth. That officer later witnessed the neonate being delivered from Fairchild’s body and watched as doctors drew blood from both Fairchild and the infant. After two weeks, the court received results that there was no genetic match between Fairchild and her infant, i.e. the third child also showed no genetic similarities to the mother as well. So, maybe Ms. Fairchild was not trying to commit fraud, but the case was still so mysterious, that it was left to hang in limbo.
In 2002, an article in the New England Journal of Medicine by Neng Yu–described a woman–later identified as Karen Keegan—who was unexpectedly identified as a chimera when she was undergoing preparations for kidney transplantation. A lawyer for the prosecution in the case of Lydia Fairchild heard of the case of Karen Keegan in New England and suggested the possibility to the defense. Lydia was able to secure appropriate legal counsel and to establish evidence of her biological maternity. The defense team and its laboratory experts were able to show that Ms. Fairchild, too, was a chimera with two sets of DNA, and that one of those sets could have been the mother of the children. Neng Yu and a team of researchers presented the case of Karen Keegan, a woman who had needed a kidney transplant. the researchers discovered that her third son was a genetic match to Keegan
It was the publication of this case–in the respected peer-reviewed New England Journal of Medicine–which offered new insight on the case of Lydia Fairchild. Fairchild was found to be a chimera, with the second set of DNA found from her cervical smear. That cervical swab eventually revealed Fairchild’s second distinct cell line, showing that she had not genetically matched her children because she was a chimera. The New England Journal researchers posited that Keegan and Fairchild were both chimeras, resulting from the fusion of two independently fertilized eggs at a very early stage of development.
Fairchild’s case was one of the first public accounts of chimerism and has been used as an example in subsequent discussions about the validity and reliability of DNA evidence in legal proceedings within the United States. Fairchild’s case prompted new concerns about the reliability of DNA evidence in the United States legal system. Fairchild’s lawyer, Alan Tindell, suggested that DNA may not be as infallible as previously thought. Fairchild matched that pattern, having one set of DNA throughout most of the cells in her body, and another distinct set of DNA in her cervical tissue. These cases challenge the blind faith which the scientific community places on the irrefutability of DNA testing. Forensic science cannot rely on DNA testing as the sole source of evidence, as it has done previously, as the criminal or victim may be a chimera. From the previous cases mentioned, current maternity and paternity testing methods will have to be re-evaluated.
In some cases, all the blood cells in a person who received a bone marrow transplant will match the DNA of their donor. But in other cases, the recipient may have a mix of both their own blood cells and donor ones, A blood transfusion will also temporarily give a person cells from someone else; but in a bone marrow transplant, the new blood cells are permanent.
Krimsky and Simoncelli stated that potentially every human being could exhibit some trait of chimerism, which they claim may impact the way that forensic scientists collect and utilize DNA in crime scene investigations. Not surprisingly, that concept is being hotly contested in the medical literature.
There is an earlier case in England that may have bearing. In 1953, the first confirmed chimera, a woman known in scientific literature as Mrs. McK, learned after donating blood for the first time that she had two different blood groups, A and O. This would have made sense if she had recently received a blood transfusion, but she had not.
A single explanation remained: one group rightly belonged to her; the other was a relic of her twin brother, who died at just three months old. Their blood cells had somehow blended in their mother’s womb; and after all those years, his were still living within her. It was, as the doctors who described her case in the British Medical Journal called it, “Nature’s experiment on Mrs. McK.” This was before the Human Genome was determined and DNA became the explanation for life, including becoming the indisputable fact in paternity and criminal cases.
Coming along with the interest of scientists in the issue, it has been found that there are numerous documented cases of fathers and mothers with chimerism—any of them potentially losing all custodial rights. The chimerism diagnosis can help with a mental health identity crisis and those that need aid.
It was concluded that both Keegan and Fairchild were both tetragametic chimeras. Prior to 2002, Fairchild had no indication that she might be a chimera, or even what a chimera was.
There are other cases from around the world which I will just mention here in passing:
The Dutch sprinter Foekje Dillema was expelled from the 1950 national team after she refused a mandatory sex test in July, 1950; later investigations revealed a Y-chromosome (suggesting malenes) in her body cells, but the final analysis showed that she was probably a 46,XX/46,XY mosaic female.
Another instance of treatment-related human chimerism was published in 1998, where a male human had some partially developed female organs due to chimerism. He had been conceived by in-vitro fertilization.
In 2008, a man was killed in a traffic accident that occurred in Seoul, South Korea. A DNA analysis to identify him revealed that his blood–along with some of his organs–appeared to show that he was female. His blood that contained female DNA, kidneys contained male DNA, and his spleen that contained a mixture of the two. It was later determined that he had received a bone marrow transplant from his daughter.
In 2019, the blood and seminal fluid of a man in Reno, Nevada–who had undergone a vasectomy–exhibited only the genetic content of his bone marrow donor. Swabs from his lips, cheek and tongue showed mixed DNA content.
