April 19, 2014

How the CCR5-Delta 32 Mutation Beat the Black Death, Smallpox, and HIV, and Gave European Whites Control Over North America

I’ve been studying genetics and world history today and thinking about the CCR5-delta 32 mutation.  Had it not developed, planet Earth would not look anything like it does.

If you are white, or partially white anywhere along your bloodline as most Americans are due to the history of slave masters siring illegitimate children with their slaves back in the 18th and 19th, you owe a tremendous debt of gratitude to a genetic mutation found among a minority of European Caucasians seven hundred years ago.  Without it, you would never have been born.

Black Death and the CCR5-delta 32 mutation

The Black Death in Europe resulted in 1 out of 2 people dying in a span of only 24 months. It took 150 years for the population to recover. Those who survived did so, in part, because of a genetic mutation called CCR5-delta 32. Today, it offers immunity to Smallpox and HIV.

Scientists have named this mutation CCR5-delta 32.  Three times in human history it has kept whites from going extinct.  Without it, almost every American alive today would never have been conceived because our common ancestors would have died, altering the course of world history.

Going further, it is fair to say that the United States wouldn’t even exist today had it not been for the mutation that ultimately made surviving plagues, poxes, and pandemics easier for a small subset of individuals who hit the genetic jackpot, forged in the aftermath of suffering, death, tragedy, and pain.

CCR5-delta 32 and Resistance to the Black Death

Between 1348 and 1350, the Black Death swept Europe and unleashed one of the most lethal pandemics every experienced in recorded history.  It is estimated that 1 out of 2 Europeans died in a 24 month time span.  Friends, family, spouses, coworkers, princes, paupers … it didn’t matter.  Imagine waking up in a world two years from now when half the people you know are dead.  It took 150 years for the population to reach its previous level.

Based on the DNA evidence, it appears that the majority of people who survived had the CCR5-delta 32 mutation, which can only be achieved when both your mother and father pass the underlying genetics onto you.  

CCR5-delta 32 and Immunity to Smallpox

Now fast forward a few centuries and witness the major smallpox outbreaks that devastate the world.  The horrible infections and painful deaths kill more than 3 out of every 10 people infected.  Yet, those who inherited the CCR5-delta 32 mutation survive just fine.  They are virtually immune to infection.

CCR5-delta 32 and Immunity to HIV

And now, you arrive at the modern day HIV pandemic.  Whites who have the CCR5-delta 32 mutation are “virtually immune” to HIV infection.  Likewise 20% of Caucasians, or 1 out of every 5, has at least one copy of CCR5-delta32, which offers “some protection” against infection and, “makes the disease less severe if infection occurs”.  

CCR5-delta 32 In the Modern World

According to David Brown in “AIDS Resistance Might Be a Legacy of Plague Survival,” in the Dallas Morning News on May 18th, 1998, only 2% of those from Central Asia carry the CCR5-delta 32 mutation, and it is absent in American Indians, Africans, and East Asians.

Think about how that shaped the world.  When Columbus showed up and the Indians died of Smallpox, a significant percentage of the European whites were immune to it.  That was an incalculable advantage in terms of survivability that made conquering the continent far easier than it would have otherwise been.

Think about the ramifications for the United States today.  The Centers for Disease Control estimate that “[a]t some point in their life, approximately 1 in 16 black men will be diagnosed with HIV infection, as will 1 in 32 black women.”  The CDC goes on to explain, “the estimated rate of new HIV infections among black men was six and a half times as high as that of white men” and “the estimated rate of new HIV infections among black women was 15 times that of white women”.

There are a multitude of causes for that disparity – poverty, education, access to quality health care – but the CCR5-delta 32 mutation continues to provide a sort of built-in redundancy plan against phenotype wipeout for those who survived the Black Death of Europe.  Seven hundred years later, it is still changing the world.  

That influences who survives, who is born, what priorities matter to elected officials.  It seems so arbitrary.

Human empires and entire bloodlines rose and fell, all from this tiny disease carried by fleas and rats, and a minor change in an allele on a handful of peasant’s DNA.

This is precisely why nature favors sexual selection over asexual selection.  It is the random mutation caused by mixing a wide variety of genetic material that provides the greatest overall chance of survival.

  • Gilvus

    From my understanding, “normal” CCR is a receptor on our white blood cells that’s basically a flashing neon sign that says “ATTACK HERE” to HIV. CCR-Δ32 is a deficiency that makes the sign not light up, confusing the HIV.

    But for some reason, CCR-Δ32 isn’t as widespread as one would believe. Wikipedia states that only 5-14% of people of Northern European descent carry one copy of the gene (meaning even fewer people express it). This is far fewer than you’d think if it helped humans survive a population bottleneck back in the Middle Ages.

    So I’d guess CCR-Δ32 is similar to anemia: it provides fitness in certain conditions (i.e. resistance to HIV/plague for CCR, resistance to malaria for anemia), but provides significant disadvantages if those conditions don’t exist (CCR-Δ32 increases risk of infection by West Nile Virus, anemia makes you weak).

    Of course, I could be totally wrong, and unmutated CCR is a vestigial feature that’s being replaced by an advanced mutation. Your thoughts?

    • http://www.joshuakennon.com/ Joshua Kennon

      That the fascinating part about it – it has to have some sort of limitation otherwise it should have already taken over the population. One possibility is the fact that very few “true” bloodlines exist anymore. I remember that story a couple of years ago in the news where the professor had his class test their blood and only 1 or 2 of the white kids were actually white. The rest were white, black, and native American because it was one big frontier bacchanalia, reproductively speaking, back in the day before paternity tests as the old and new worlds collided. That could have introduced significant diversification of the genome.

      If your last paragraph turns out to be the case, we likely won’t know for another few thousand years. It’s entirely possible the mutation could become the new “normal”. Then again, all it could take is one super-freak bird flu that kills only those people with the mutation and suddenly it gets knocked off the genome success path, again. That is what makes it so interesting to me. It would dangerous, were we capable of such genetic manipulation, to change everyone to be immune to HIV. It could inadvertently make us susceptible to something worse. For example, I can’t imagine how hard it is to live with HIV given the horrific side effects of the drug cocktail but ebola is far more terrifying.

      • Gilvus

        Hard to say, right? I disagree with your article because more than one outbreak of the bubonic plague originated in or around China (sorry ’bout that). If Δ32 were solely responsible for plague resistance, I wouldn’t be alive today. I’m sure it played a role in shaping the world today, but I don’t think it’s nearly as important as your article insinuates.

        Here’s an interesting article that finds Bronze Age frequency of Δ32 is similar to what it is today. It’s abstract-only, so I don’t know their methodology or sample size. Every time I see “pay $39.99 for this article” I die a little bit inside. The related links on the right side corroborates this finding.

        • http://www.joshuakennon.com/ Joshua Kennon

          Wouldn’t China have an enormous advantage in a bubonic plague outbreak so many centuries ago, though, given that most of the population was rural and the nation itself was much larger than the white-only Northern European nations?

          The mutation wouldn’t be necessary because there was so much distance to cover, some villagers and population centers in China were bound to survive, or avoid infection altogether.

          That would seem consistent given that Asians are the only other population group to have the mutation.

          P.S. I read your “sorry ’bout that” as if you were responsible for the bubonic plague in China. With such powers, and the title of ‘professor’, you are clearly preparing to become a comic book arch-villain.

        • Gilvus

          Population density would only affect the transmission rate of the
          disease, not the extent. The extent of the disease (i.e. what % of the
          population was infected by this particular strain) is governed by how
          far the disease vectors – the fleas – can travel. The Black Death
          emerged during the height of the Mongol Empire, a time of prosperity and
          unity when the Silk Road was bustling, and pretty much all of Eurasia
          was interconnected by trade.

          I’m sure that some truly-isolated communities that rely on subsistence farming may have been spared, but only small pockets of humans can get by on subsistence farming alone. The vast majority of the rural communities would occasionally travel to the nearest city to trade, then bring back the plague with them.

          Plus, about a third of China’s population succumbed to the plague, so there must be some other factors besides Δ32 playing a role in survival. It’s unreasonable to assume that all of the people exposed to the plague died.

          As for the comment, I was apologizing on behalf of my ancient ancestors for inflicting a terrible plague on your ancient ancestors. It’s kind of like saying “I’m sorry that my great-aunt’s sister-in-law’s cat ate your second-cousin-thrice-removed’s best friend’s goldfish.”

    • jcutter2

      1) CCR5 doesn’t act like a neon sign. Its a receptor for CCL5, protein that acts as a chemo-attractant, and CCR5 happens to be a receptor for HIV-1 too.

      2) Evolution takes a long time, so no not everyone would have this mutation. The only way that everyone would have this mutation is if everyone except the people with this mutation get AIDS and died.

  • dfrankmd

    Incorrect statement: “Based on the DNA evidence, it appears that the majority of people who survived had the CCR5-delta 32 mutation, which can only be achieved when both your mother and father pass the underlying genetics onto you.” Actually you have the mutation is one parent passes it on but you also have non-mutated CCR5. If both parents pass on the mutation then the non-mutated CCR5 is absent. There are 3 levels of resistance: Homozygous mutant (most resistant), Heterozygous (partial resistance due to less non-mutated CCR5) and Homozygous non-mutated (non-resistant).