When I was small, I felt I had a twin who was lost somewhere. My mother told me, no, I was born alone, just me. The feeling would not go away and later I explained it as undigested grief as a result of a younger brother who died in infancy, whose absence was more profound than his presence (I was a toddler when he died, not quite two years). Or perhaps it was ancestral memory, or just routine compartmentalization of the multiple personalities we all develop and carry through life.
Since then, I’ve read about Vanishing Twin Syndrome, where one twin not healthy enough to survive either miscarries, is reabsorbed by the mother’s body, or absorbed by the healthier fetus. This is not unusual. By one estimate, 1/8 of all pregnancies begin as multiple pregnancies, but 20-30 percent of those result in just one child. Other estimates are much higher. Before ultrasounds, mothers and doctors were often unaware of the existence of a second fetus.
Sometimes, the vanishing fetus becomes a teratoma in the surviving twin, a tumor with teeth and eyes. In some cases, surviving twins are found to have extra arms and legs inside them, while yet others are blended:
Two early stage embryos fuse into a single embryo containing two unique sets of DNA. The surviving twin becomes what’s known as a chimera, essentially two people in one body. Chimeras can have different sets of DNA in different body parts. For instance a male chimera can have one type of DNA in his skin cells but what appears to be an entirely different person’s DNA in his sperm cells.
Most chimera are unaware of this, but occasionally it manifests outwardly, as two different eyes, for example, or in an intersex person with both male and female genitalia.
I’ve been told many times I have two different eyes, one bright and open, one more hooded and jaded, as if there are two of us looking out.
And you? Do you feel like a singleton or a chimera?
Read more on the subject here. (Thanks to Althea Hayton for the last link.)