The How Of Y: Alas Poor Yorrick, We Knew Him Way Too Well

I’m not geneticist. I’ll say that up front. I took genetics in college and even though I have a degree in biology, my subspecialty was evolution/ecology which, while related, is a whole different can of worms. So apologies to all the geneticists out there for mistakes I might be about to make.

Last week I named Brian K. Vaughan and Pia Guerra’s Y: The Last Man as one of my favorite Indie science fictions books. But I also claimed that it was more along the lines of soft sci-fi in that it dealt more with sociology than with physics, which is all well and good for the purposes of the story. If anything, BKV is a writer who was able to convince me that the science doesn’t always matter. A story is not necessarily satisfying because of its plausibility or capability of explaining exactly how a contrived scenario came to be. Then he went off to write for LOST but the less said about the hole that show fell down the better.

But the ending of Y (insert SPOILER WARNING) does leave us with a very intriguing question concerning societal rebuilding. I’m seriously about to get very spoiler-riffic here so do not continue if that might bother you. Everybody still with me? Great.

So at the end of the book we’re left with 2 genetically distinct men on earth: Yorrick and Vladmir. It seems like the world focuses on cloning Yorrick because Vladmir is off running Russia. Here’s the primary issue: cloning doesn’t work as well as sex. Eventually you need to get your society back to sexual reproduction. Sex acts like a remix for genetic material; it takes two sets of potentially screwy DNA from mother and father and zips them together into something that should work pretty well. The alternative is making a copy of a copy of a copy of a copy forever. And anyone who has tried that trick with a Xerox knows that after enough copies of copies you’re left with an unreadable document. This is because a Xerox isn’t perfect, and thus tiny imperfections are left on the new copy of the document. And eventually those imperfections accumulate to the point where you’re left with an unreadable document.

This happens in biology too and is known as Muller’s ratchet. It was discovered in certain species of lizards that are all female. That’s right, there are no males in the entire population. The species reproduces by laying unfertilized eggs that hatch as genetic copies of the mother. And much like the Xerox, biology is far from perfect, so any copying errors in the DNA of the mother are passed onto the offspring. And so forth and so on until after enough generations the eggs laid do not produce viable offspring because they’re DNA is too corrupted. Thus each mutation (or copying error) cranks the ratchet forward a notch, and without sex to remix the errors the ratchet can’t ever be turned back. So while you save a lot of effort avoiding dealing with males, it’s a short term strategy for the species as a whole.

Well how does this apply to Y? Because at the end of the story we have access to two distinct males and cloning technology, thus we’re supposed to walk away thinking the crisis is solved? I say not so fast.

First of all, why are you cloning Yorrick? Yorrick is able to breed just fine, all he needs is a woman, there’s no need to clone him at all. All you’re doing is setting yourself up for a wicked Muller’s ratcher. Because as smart as Dr. Mann is I’m sure her cloning technology is far from perfect. The problem is the entire story is about Yorrick NOT wanting to be put out to stud, so the ethical implications of forcing him to do just that give one pause, but there’s no saying that one or many of his clones wouldn’t be willing to repopulate old fashioned style.

This is where it gets complicated. So you have cloning happening while a generation of Yorrick copies is also presumably having babies. All the daughters of Yorrick will, for all intents and purposes, be cast aside, because they’re siblings or offspring of the only available men on the planet. Raw deal. But now we at least have a generation of men with some genetic diversity, which is good, but who do they pair off with? Everyone of their generation is their sibling. And even factoring in Vlad once the second generation has produced the third generation everyone is still related, having Vlad around only buys you one extra round of babies. I tried to diagram what this would look like, trust me, it’s a mess and you’d probably be less likely to get the basic idea if I avoid throwing figures and numbers at you. So here's a picture of a tree with monkeys. Enjoy the imagery!

The solution would seem to be cloning the women that survived the plague to keep a generation of new women available at the same age as all the men produced with each new generation of offspring, which is something they allude to in the final issue of the series. This is going to take a lot of coordination, effort and resources. And you’re going to have to do it for a long time to get any appreciable level of genetic diversity, because instead of infusing new genetic material you’re going to have to wait for random mutations to slowly diverge different lineages apart until they’re different enough to start intermingling sexually again.

Scientists call this problem a genetic bottleneck (ironically a problem that also happened in Genesis, twice) where there are so few members of a species left that incest is unavoidable. This leads to all sorts of problems, the obvious ones like genetic defects but also more subtle things (e.g. cheetahs have no immune response against any other cheetah’s tissue, even when it’s grafted to them).

Genetic diversity is good, you want as much as possible in a population because it acts as a buffer against problems. If everyone is very similar a bad disease can take out the entire population. It’d be like if everyone was running Windows and the perfect Windows-destroying virus was created we’d all be doomed. But since we have Mac, Linux, Unix, etc. we have a buffer against something really bad happening to everyone. And again, BKV does right because he mentions something about new "strains" of Yorrick (, and as usual BKV doesn't elaborate), which sounds like artificially induced diversity, but I'd still argue sex is the way to go.

And if the deficiency of variety isn’t quite problematic enough, I haven’t even touched on the ethical implications this kind of social engineering would have. The world at the end of Y is almost Utopian, but apparently there’s very little freedom or reproductive rights if they actually wanted to keep the human race going, which was kind of the goal all along.

My point is that as much as Y was a wonderful exploration of the world without men, the solution at the end of the story still leaves the world in a lurch, and it’s a lurch worth thinking about, as much as it hurts this non-geneticist’s head. And seriously, besides genetic recombination, I'm not sure the world really needs men. And that's me speaking as a biologist.


Ryan Haupt still can't read the last issue of Y: The Last Man without crying. Here him get confused by genetics audibly on the podcast Science… sort of.


  1. I wonder if it might be a manageable problem. The new generation would not all strictly be siblings, they would be half siblings. Each child would have half of their DNA from Yorick and half from the mother.  Given a large enough population and some careful gene sequencing, you should get some pairs that each got separate halves of Yorik’s genome and have little or no overlap. In a lab, you might even be able to create this situation artificially. Those pairs could mate and while a significant number would have a significant amount of Yorik DNA, there should also be, given a large enough sample size, some new offspring that have little or none of Yorick’s DNA. If left to random chance, just by dumping a bunch of Yorick clones into the population, you would likely end up with a huge genetic bottleneck and all the problems that come with it, but with careful sequencing and selection you could eliminate Yorick’s DNA from the population in the 4th generation.

    Except for the Y chromosome. If Yorick has the only Y chromosome in existence, then every male for all time will continue to have tha chromosome, but even that will change over time with mutatation and other gene swapping events. But the Y chromosome is relatively safe from an inbreeding standpoint. inbreeding causes problems when both copies of a chromosome are exactly the same. It can’t happen with the Y chromosome because only men have a Y chromosome and the only have one. 

  2. Very interesting read.  Well done.  I’m off to hunt down some cloned women.

  3. Awww, Haupt! You’ve ruined my one man, many women dreams, and crushed any potential stories involving a king running an army of his children. At least, for very long…

  4. I really need to read this again. It’s been a while.

  5. Thanks for another great article, Ryan. Science is hard, but you make it easy.

    Although you left out one additional advantage to sexual reproduction: it’s more fun than cloning!

  6. ” . . . which sounds like artificially induced diversity, but I’d still argue sex is the way to go.”  Amen, brother.

  7. The first few generations of Yoricksons might not be breeding with ladies their own age. The social rules are going to bend a little when, to avoid inbreeding problems Chris pointed out, the new men have to look for older women to make a ‘good’ match, genetically speaking.

  8. This was a really great analysis of the end of Y. I thoroughly enjoyed it. Much food for thought! Well done!

  9. Wouldn’t the genetic make up be somewhat similar from the first generation of offspring Yorick produces from intercourse (this is assuming we’re ok with the kissing half-sibling effect of siring a 2nd generation from Yorick’s kids).

    Geneticists recently speculated that the cultivation of the human race needed no less than 20k individuals to disperse the genetic material enough and any less would cause the race to mutate out of existence.

    Great article! Can we mythbuster this? I’ll gladly offer myself as test subject. 

  10. I sort of stopped reading Y around issue 25. But wouldn’t the world have a larger problem with all Males of every other animal species also being dead? I remember thinkin about how completely screwed the world was for that reason alone in the early issues.