The Vanishing Twin

Human reproduction is messy. It turns out that there are more combinations than just plain male and female. It’s when you enter the world of DNA testing that you realize just how odd things can get.

Suppose you run a test and it shows that a girl’s mother is also her uncle. No, that’s not a mistake in the lab. It happened and the results were replicable.

The odd result is the byproduct of a “chimera” basically an embryo that disappears prior to birth. It’s the case that up to 30% of pregnancies that are diagnosed as twins result in the birth of only one child. The other embryo is reabsorbed by the mother’s body. However, the vanished embryo can leave DNA remnants in the surviving twin.

Think about it for a moment. We’re talking about a woman’s body spontaneously aborting an embryo. For those religious extremists who would criminalize abortion, what do you do with that? Arrest God? No, miscarriages and spontaneous abortions are normal medical events. Typically unwanted, but so are a lot of things in life.

The article in “Grid” also points to another case in Washington State in which a woman almost lost custody of her child due to weird DNA results. It’s bad when bigots don’t understand how the human body works. worse when the state family care system is similarly ignorant. Still worse when local police departments systematically, incorrectly interpret DNA test results.(2) When processing errors are added to unusual DNA results, test results are as likely as not to be wrong.

How weird can DNA results get? In a known case, a woman’s saliva contained XY (male) chromosomes from a vanished twin while the rest of her body had normal XX (female) chromosomes. Routine DNA tests relying on saliva samples indicated that the mother could not be the mother and the father could not be the father. In-depth testing debunked the superficial finding. However, a lot of legal and emotional damage can be inflicted before the correction.

We also have cases in which a child may have 27 chromosomes per cell instead of the normal 26. That can trigger a range of mental and physical health issues.

An interesting question is whether human reproduction is becoming more problematic due to the impact of pollution on body chemistry. We haven’t had DNA tools for a long enough time to be able to discern a trend.

Growing up in Kentucky, I heard the oft repeated argument that humans had to be created by a god because of our complexity. However, as we learn just how messy our body is, you have to ask, who the heck would want to take credit for that? What “creator” would do such a sloppy job?



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