Page 20: CCR-5 Receptor Mutation

Without doubt, my favorite things to write in Old Blood were the genetic discussions. I just love them. I wish I could write books on it, like Matt Ridley. His book, Genome, is a perspective changer.

The CCR-5 mutation is an incredibly cool thing that didn't really get a lot of space in the book. So here is a more straightforward telling of the tale:

The way to think about the mutation is this: If you thoroughly spray a nest of, say, 1000 cockroaches with a particular poison and 3 or 4 survive the treatment, what you have neatly done is find the 3 or 4 cockroaches that are immune to the poison. Bingo, you've committed evolution! You have, in a moment of poisonous spray, selected for a particular genetic trait. If the 3 or 4 cockroaches go on to make some baby cockroaches, most or all of their offspring will also be immune to the poison because they inherit the immunity gene from their parents.

The beautifully ironic thing about our 3 or 4 cockroaches is that their immunity gene was probably a reproductive mistake, a flaw, or, more colorfully, a mutation. A mutation that saved their lives.

On a much larger scale, the waves of disease that have washed through the human population, including the black death, cholera, and small pox have acted just like the roach poison above. They, by and large, killed almost everybody that wasn't at least partially immune. Because there wasn't advanced medical care back then, the diseases made a fairly "clean sweep" of the non-immune.

The immunity in humans was likely conferred by a mutation in a receptor, sort of like a door, through which infections sneak into cells. In other words, a few people had a flaw, a mutation, in their CCR-5 receptor. Their flaw was their savior. Correction, the mutation was OUR savior, because if you are of European descent you likely share the mutation. Most of us are mutants.

And we are lucky, for it was not a skill that enabled our ancestors to survive, but rather a lucky genetic break. But isn't all talent some form of genetic lucky break? A big question for human society is whether something that is subject to inheritance and probability is a legitimate differentiator. We tend to be okay with hard work: If hard work made you wealthy you get a smattering of applause. On the other hand, we tend to dislike luck and absolutely loathe inheritance. Many argue that because wealth is often tied to inheritance or luck rather than skill or hard work that confiscatory taxation is justified. Or consider another example, does the inherited hardiness of your genetic stock entitle you to a lifetime of reduced medical costs, or should you pay your "fair share" despite your "innate talent" for surviving disease? What about intelligence? When we all have to get on a spaceship to escape the asteroid, does being "lucky" enough to be smart guarantee you a spot on board? After all, to be smart is to have, at least in part, inherited good genes. These are difficult questions.

Equally difficult is the question of biodiversity. What if our 3 or 4 surviving cockroaches are highly allergic to, something they haven't yet encountered, say, pine nuts? What if being allergic to pine nuts was somehow related to their ability to survive the poison? The lucky survivors would carry a valuable immunity but also a fatal flaw that might not allow them to survive their first contact with pine nuts.  Their luck with poison could be placing them a moment away from extinction.

To wit, what if all the professor-types we shoot into space are too weak to move the big rocks on Planet X. Oops, we should have sent some other folks, too. It's hard to know in advance what will aid survival. Genetic selection is HIGHLY subject to the laws of unintended consequences. [This will form a big part of Bad Blood, on which I am working now.]

Some scientists believe the modern phenomenon of allergies (which have demonstrably gotten more intense over the centuries) is related to diseases such as cholera. The survivors of cholera had an incredibly sensitive, some might say jumpy, immune system that reacted quickly to fight the disease. Those hyper immune systems now go off like alarm bells at the first sign of invasion by, well, pollen. So what was once a BIG blessing is now a minor curse. But it is still working for us, even if we are all sniffly.

Speaking of working for us, it is also thought that CCR-5 mutation is offering at least partial protection against HIV, which may explain why the disease has been more prevalent in Africa and Asia than in Europe or the United States. Another lucky break.

So being lucky is good, luck got us here alive. And now? Embrace your flaws, they may save your life someday.