There's a reason I do software, as opposed to other technical professions: it's deterministic. I can make sense of it. If there's a memory leak, then there's always a memory leak, and it's my fault that it's there. And if the leak comes and goes, it always comes and goes; and when I can figure out the pattern, I'll know where the leak is. There's always a pattern, and it's always deterministic.

When you get into the physical sciences, however, things get fuzzy; and when you get into wetware (chemistry and biology), things get downright slippery. Yes, there's a determinism of a sort at work; but the number of ways in which things can go wrong is just huge. Frankly, if we didn't prove otherwise by existing, I would say we are impossible.

Yet we exist, despite all that could go wrong; and sometimes, despite it actually going wrong, we manage to cobble together a workable life.

While researching calico cats, I came across this article on chimerism, which sounds like the inspiration for one of Stephen King's creepier works. And that article led me to this one, about a woman who learned that the children she gave birth to were not hers. Instead, they are children of her fraternal twin sister; only she never knew she has a fraternal twin sister.

See, the fraternal twin sister is her. Some of her is made up of DNA from one fertilized egg; but some of her is from another egg. Early during her development, the cells from the two embryos came together, rather than developing separately. And while this could've been disastrous — probably happens more often than we know, and probably is disastrous in most cases, leading to a spontaneous abortion — in her case, the two sets of cells were able to work things out. They shared the responsibilities of making, well, her. The cells that make up her skin and hair came from one embryo, while the cells that make up her uterus and ovaries came from the other.

So DNA testing that compared her skin and hair to that of her children "proved" that they couldn't be her kids. The two different parts of her body are no more related than any two siblings (roughly 25% common DNA).

And she's not alone. 30 such cases are known. And the chimerism may be more rampant than that:

In fact, some researchers now think that most of us, if not all, are chimeras of one kind or another. Far from being pure-bred individuals composed of a single genetic cell line, our bodies are cellular mongrels, teeming with cells from our mothers, maybe even from grandparents and siblings.

It seems that the placental barrier isn't perfect, and that some small number of cells cross from the mother to the fetus, and vice versa; and that these fetal cells in the mother can survive for decades, and might even propagate to later siblings.

All too weird for me. All too non-deterministic. Give me the simple world of binary values and logic and design. I can make that work. But this wetware has too many variables for my poor head to keep straight.

The world is a very strange place...