It is absolutely impossible for humans and even for animals to possess two brains inside its single skull-cover. No human being is ever reported to have carried more than one brain inside its head. However, researchers have found that there were rare cases where individual humans had to bear the burden of two heads on their single bodies: They were born with more than one head. What happened in such isolated but rare cases, was that women gave birth to single bodied infants, each infant carrying more than one head on its body.
Experiments of Russian Scientists P Anokhin and T Alexeyeva and English Scientist Shrewsbury had revealed that there exist independent nervous systems inside each of the heads on the single body.
From time immemorial, human thoughts had conceived the idea of individual humans as well as individual divine entities with more than one head. In this respect, Hindu Epic Ramayana is an incredible example. Ramayana portrays the amazing story of Ravan, the belligerent enemy of Rama the hero, bearing ten heads on his single body. Another story in the Hindu Mythology is about the God Brahma who is the Creator of the Universe. Brahma carries four divine heads on the top of his body.
Those are the stories of the epics and the mythology: Leaving aside the epics, keeping behind the mythology, we come across cases where individual human beings were born with more than one head, each head containing brain of sensory sensibilities. Mostly they are twin-headed persons. Such twin headed individuals are known as conjoined twins. They are also known as Siamese Twins.
The latest reported birth of a conjoined twin took place in the year 2011 at a Brazilian hospital. Though they are not having two independent bodies, the twins are named after Jesus and Emanuel on the basis of their head-counts.
Neuroscience has convincingly proved that brain is the store house of intelligence: Brain controls and executes all human actions. Brain invents and executes all means of existence. Ancient thinkers had identified the relevance of human brain in matters of intelligence and exemplary actions. That ought to be the reason for the thinkers to conceive the idea to assign more heads to Brahma and Ravan for their exemplary intelligence and extraordinary actions.
In real life situations, conjoined twins cannot be said to have more intelligence compared to ordinary, normal human beings. Most conjoined twins did not survive for long. The life of those which survived was miserable; they could not move around freely; they could not eat and drink as comfortably as others could do. Their day to day existence was bother for relatives and the people around. That apart, functioning of the nervous system of the conjoined twins, in majority of cases, was found inadequate for adaptation to the changing environs:
A conjoined twin has common blood circulation and common system of ingestion whereas as its sensory experiences are separately executed by the separate nervous systems in the separate brains. The Russian scientists carried out their experiments on a pair of conjoined twins named Ira-Galia and Masha-Dasha. When the scientist injected a medicine for small pox, the chemical substance of the injection was found in the blood stream of both Ira and Galia. It proved that the twins had common blood circulation. The distinctness of their nervous system was confirmed by their anatomy and independent sensitivity: When a painful sensation was applied to the hand of one of the twins, say the hand of Ira, it elicited a defensive reaction from Ira and no reaction was observed on Galia. When one of the twins yawned and went into sleep the other one was awake and enjoying the sight of a toy that was placed before it. These experiments proved that conjoined twins have independent sensory experiences while retaining common blood circulation and ingestion. The discovery is indicative of possible conflicts among the twins in matters of likes, dislikes, love, hate, compassion, anxiety and emotions.
Conjoined twins are not like ordinary twins where women give birth to more than one child out of one pregnancy. In such births the infants are separate with independent bodies and heads. Their birth would be normal and they would come out of the womb, one after the other. Conjoined twins are twins only with reference to the number of heads and not with reference to the number of bodies. In fact, a conjoined twin is an individual of one entity except for the number of heads containing independent nervous system the individual bears.
It is still not clear as how woman conceives conjoined twins? There are two ways by which twins are conceived: Ovulation results in the release of more than one egg once in a while, even though during a normal menstrual cycle a woman has one dominant follicle and releases just only one egg. If two or more eggs are released, that would result in the birth of twins. However in certain situations even if only one egg has been released it gets split into two which would entail birth of identical twins. In extreme circumstances the split of the one egg does not complete all the way but will remain partially joined together. Such occasions create ‘one body with two heads’ equation for the birth of conjoined twins.
Generality decides norm. Majority is the deciding factor for generality: Every human being, including twins, whether fraternal or identical, has one body and one head. A person with one body and more than one head is out of generality and therefore, not the norm. Still, conjoined twins belong to the same species as humans do. They are parented by humans and they remain with the same genetic qualities as those of their progeny.