
Here is the story of a pair of conjoined twin sisters who were taken away from their parents at birth and used as the subject of numerous dehumanising scientific experiments.
Conjoined twins are rare, with the BBC stating that they account for one in every 500,000 live births in the UK. Globally, conjoined twins are thought to make up anywhere between one in every 50,000 to 200,000 births.
One of the most notable stories of conjoined twins was that of Russian sisters Masha and Dasha Krivoshlyapova, who were the oldest living pair at the time of their death in 2003.
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Born on 3 January 1950 in Soviet Moscow, Masha and Dasha would be separated from their parents just moments after being born so USSR scientists could use them for experiments.
The girls' mother would be told her children had passed away shortly after birth.
As their parents grieved, Masha and Dasha were whisked away to a hospital in the Moscow region and handed over to Soviet scientists and, according to author and journalist Juliet Butler, subjected to a series of cruel medical experiments for the first six years of their lives.
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Butler, who would go on to write her book The Less You Know the Sounder You Sleep about the sisters, learnt how Masha and Dasha were essentially tortured by scientists in the name of furthering their understanding of science.
The sisters were considered valuable to Soviet authorities because they shared the same blood system but had separate nervous systems, which meant that scientists used them as test subjects to differentiate between the two.
"They wanted to know more about the body’s ability to adjust to conditions like sleep deprivation, extreme hunger and extreme temperature change," Butler said (via Macleans).
"They were seen as the perfect human guinea pigs."
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In order to conduct these experiments, scientists would force the girls to be injected radioactive iodine, electrocuted, burned, and frozen for their own research benefits.
In 1956, three years after the death of notorious dictator Joseph Stalin, the girls would be taught to walk and talk, before being transferred to a boarding school away from the capital to continue their education.
They would briefly be reunited with their mother during the 1980s until Masha - the more assertive and dominant of the twins - decided to break of contact with her on both twins' behalf. Butler would meet the pair in 1988, during a period of social change in the USSR, after they appeared on a talk show to appeal for better living conditions.
Speaking about the difference in personalities, Butler described Masha as 'self-centred and egotistical' yet 'charming' while Dasha was 'kind, gentle, generous and quiet'.
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She would remain in contact with the sisters for a number of years until their death in 2003 at the age of 53. Masha, who had long struggled with alcoholism, would die first from a heart attack. Dasha would die 17 hours later, as the toxins from Masha's decomposing body seeped into her system.