Browser BBC Earth talks about the two-headed creatures that exist not only in ancient myths.
It was a chilling sight. Snake-like monster, many-headed Lernaean Hydra out of its lair and unleashed its fury on waiting for her Heracles, the son of the Greek God Zeus.
But Hercules had a plan. He already knew that in place of the severed heads of the Hydra grow new, therefore, called on the help of his nephew Iolaus.
I’m pretty sure they watched the creatures with such anomalies in nature
As soon as Hercules cut off the Hydra’s heads, Iolaus cauterized the wound with the torch, and new heads this fiendish creation has already appeared.
The Hydra hissed and writhed, its poisonous blood and breath threatened with death the greatest hero of Greece, but he still prevailed.
The last head of the beast fell to the ground, and Hercules came out of this battle victorious. Now he could proceed to the third of the twelve of his exploits.
Many-headed creature with poisonous breath and grow back body parts — surely a figment of rich imagination.
Some authors argue that the Hydra fifty heads, while in other stories they are much smaller.
But where did such an unusual idea? Is it possible that the prototype of the Hydra was the many-headed serpent-a giant, really existed in nature?
Scientists record the birth of two-headed animals for many years. In 1940-ies researcher L. E. cable described the double-headed embryo of the fish-needle. He called it “tiny monster”.
In the lab of a specialist in developmental biology Arhat Abzhanov from Imperial College London, visited a lot of two-headed creatures.
Thanks to modern knowledge in the field of genetics he was able to identify mutations and cellular anomalies that could cause this phenomenon.
It is possible that the source of inspiration for the creators of ancient myths, it served as such natural phenomena.
“I’m pretty sure they watched the creatures with such anomalies in nature and tried somehow to explain this phenomenon or reflect it in their culture,” says Abzhanov.
From time to time two – and even three-headed individuals really are born in the wild and in captivity. Interesting is the fact that this phenomenon, known as polycephaly, found in various species of animals.
Take, for example, underwater world. In 2013 in the Gulf of Mexico was discovered a two-headed bull shark embryo.
The following year the same individual was found among marine mammals: one of the Turkish beaches were found a Dolphin with two heads.
Apparently, in both cases, it was Siamese twins that developed from one egg, which after fertilization will not be separated completely.
This anomaly is observed in humans. Often Siamese twins not only have two heads, but a double set of internal organs and even limbs.
Because of his famous experiments of the early XX century biologist Hans Spemann was able to prove that it is possible to artificially prevent the separation of fertilized oocytes and Siamese.
He wanted to understand how the embryo develops. He put together two embryo salamanders at an early stage of development with baby hairs.
He found that with these manipulations, you can get the Salamander with two heads, who fought among themselves for food, despite the fact that the body they had only one. Scientist named it being “two selfish people in one body.”
The list of animals, among which there are double-headed individuals is quite large. It includes turtles, snakes, kittens and other.
We also know that such cases are not peculiar to modern times. Paleontologists have found fossilized two-headed embryos, the age of which consisted of millions of years.
As noted Abzhanov, the cause of numerous goals or individuals can serve a variety of mechanisms.
He explains that the head as the body is an example of convergent evolution — process by which individuals of totally different species groups are developing similar features.
Head are animals with backbone and without him, although the relationship between them is missing. Apparently, the head is a useful result of adaptation common to many organisms.
“Head really is a very effective body — explains Abzhanov. She just needed to study a new situation.”
That is why the head has so many sensory organs, including eyes, ears, nose and mouth.
Head shape and facial structure by genes, one of which is of particular importance and, in particular, is responsible for the width of the face.
He has a curious name — Sonic Hedgehog, or SHH (in honor of sonic the hedgehog, the hero of the popular video game Sonic the Hedgehog).
It is connected with family genes Hedgehog (HH), first found in fruit flies. As a result of mutations of this gene in larvae of these insects appear sharp outgrowths similar to ezinye needles.
The SHH gene are the only vertebrate animals. Abzhanov explains that in the case of attenuation of Hedgehog signaling pathway in the development of the embryo, his head gradually tapers.
In some cases it can deform so that the light will be a creature with one eye like a Cyclops. A substance that causes similar anomalies in livestock, including sheep, received the appropriate name — cyclopamine.
It is found in convolvulus arvensis, which may accidentally eat a pregnant female.
What happens if the signal is SHH, on the contrary, increase? This will lead to the opposite effect — my head will expand up until it appears with two faces.
“This mutation is rare, but such cases were recorded among wild and domestic animals,” says Abzhanov.
From a technical point of view, the individual with two faces and two heads are two different things. According to the observations Abzhanov to the animal on one body had two separate neck and head, early development should occur a different genetic error.
“The formation of the head, as well as any other part of the body, runs a special group of cells in the early embryo development. We call it the organizational center,” he explains.
This mechanism was opened thanks to Spemann experiments with the embryos of salamanders.
“If you take a group of cells and to transplant them, for example, the embryo of the frog, it will have two heads. This suggests that these cells serve the body a signal about necessity of formation of the head,” says Abzhanov.
The same thing happens in the case of Siamese twins, but Abzhanov observed similar processes in his laboratory.
Cells of the organizing centre can accidentally get from one embryo to another as a result of the injection or incision if surgical instruments were not properly handled.
Scientists are trying to understand what leads to such violations of the process of development of the embryo. Abzhanov notes that one of the factors may be the ambient temperature.
Together with his colleagues he often studies in the laboratory, fertilized chicken eggs, which he delivered from the farms. They noticed that in hot weather, strange things happen.
“The eggs that we receive during periods of hot weather when the air temperature exceeds 30C, revealed more anomalies, including the more common double-headed embryos,” he says.
This trend noted by other scientists. For example, one biologist found that the increase in temperature in the reservoirs can lead to the emergence of two-headed embryos of fish Danio rerio.
The causes of this phenomenon have not been studied, but currently, scientists conduct research designed to clarify the relationship of high temperature and appearance of anomalies.
It is likely that biology was the source of inspiration for the authors of the myths, but the opposite is true: myths are also a source of inspiration for biologists.
In 1758 the Swedish botanist and zoologist Carl Linnaeus named in honor of the Hydra group of tiny marine creatures, something similar to it.
These creatures are of particular interest because they have multiple serpentine appendages and the ability to regenerate just like the Hydra, slain by Hercules.
However, it should be noted that a double-headed species, including Siamese twins, have very little chance of survival. They rarely overcome the embryonic stage of development and almost never survive to adulthood.
The growth and development of individuals with two heads experiencing a huge load, and scientists have again seen in 2014, when the lab of the University of Haifa in Israel has a rare two — headed Salamander. Spemann for sure it would be a delight.
It has attracted a lot of attention from the media, but lived very long.
“The two-headed salamanders are rare, explains Leon Blaustein, who was in charge of the above mentioned laboratory. — In larval stage, all was well, but after metamorphosis individual has died”.
The larva of the Salamander is the tadpole, which becomes adult in the result of a metamorphosis, losing their gills and some fins.
His head is also undergoing significant changes. Develop you tongue and teeth, and the mouth becomes wider. Perhaps, these dramatic changes led to her early death — the answer is nobody knows.
Abzhanov admits that, in addition to the observation of the real two-headed animals in nature the Greeks could inspire other phenomena. He explains that during mating, the snakes often gather in balls.
“Seeing such a spectacle, you can imagine that before you is one snake with several heads, he says. — Looks very scary.”
And indeed, the image of the Hydra, represented in ancient paintings, very similar to the picture described above.
Polycephaly is a very unusual phenomenon that can cause fear in people — this is the feature of our psyche. This partly explains why the abnormality was chosen in order to give the Hydra from Greek mythology frightening.
Faced with polycephala, people really feel discomfort — this is evidenced by the history with the two-headed Salamander of Blaustein and “tiny monster” cable.
In the first case, people have even started to build a conspiracy theory.
“Everything started to spiral out of control when various groups started complaining online that the point of radiation, — says Blaustein. — But the reason remains unknown.”
Hydra — not only in mythology, a creature with multiple heads. Making his twelfth exploit, Hercules had faced a three-headed dog Cerberus.
In Japanese mythology there are wasmerely dragon Yamata-Orochi but, as in the Slavic three — headed dragon.
The image of multi-headed creation in literary works always symbolizes the many dangers that cannot easily be overcome.
Thus, we can assume that there is a whole culture associated with the intimidating effect produced on people creatures with multiple heads.
The phenomenon of polycephaly in animals remains unclear. However, given the fact that individuals with two heads have very little chance of survival both in captivity and in the wild, there is no reason to assume that this feature will not remain a rare anomaly.
One wonders how the authors of the classic myths drew their ideas. It is possible that in ancient times someone saw an animal with two heads and began to talk about it overly embellished stories.
Over time, these stories could grow more and more incredible details and in the end turn into the legend known to us now.