My friend, The Lorax, posed me with this question: “If you cut Wolverine in half, say with an adamantium sawmill, would each half regenerate into a full Wolverine?”

Before answering the question of how Wolverine's body would regenerate, we should first understand how regeneration happens. Though it's commonly understood that reptiles regenerate lost limbs, this is actually untrue. The only vertebrate animals that regenerate are the urodele amphibians. (Lizards can partially regrow their tail, but the copy is never as good as the original.) Only these amphibians can lose a limb and regrow it to be perfectly. How the urodeles regenerate is a process called "dedifferentiation," whereby specialized cells regress to a more basic, less specific form. Sort of like the cells you have in your body now becoming stem cells--though the exact cells the amphibians create are NOT stem cells.

These cells then go on to rebuild the missing body parts in large part by becoming that body part. The exact mechanism isn't exactly understood, but the general principle is there for us to move on.  

Now for the case of Wolverine, it's important to note that two things have to happen for this regeneration:

1. a wounded sheath must scab over the amputation area;

2. nerve cells must be present.

I will allow that Wolverine may not need the sheath, just because he's awesome like that. But Wolverine will need nerves. How else, after all, would he even know that half his body is missing? No individual cell on his body could tell that any other individual cells are missing.

Does this neurological fact mean that only his brain half could regenerate? Not exactly. If you cut off the limb of the starfish, then it will not only regrow it back, but the limb itself will regenerate into a new organism.

If we were to give Wolverine's lumbar spinal cord a lot of credit, then it should be able to tell that it's been cut off from the top of the body and send messages to the nerves to begin regenerating the top half of the body. When I say the "nerves know," I don't necessarily mean the "brain knows."

However, all this talk of biology may be ultimately moot simply because of the basic laws of physics. Our bodies are made of food. More accurately, our bodies are made of atoms that we acquire by eating food. Of course, food is not just atoms, it's energy, but we'll leave that aside for now because we're talking about building the body, not running it, so it's better to simply focus on the raw materials needed.

One of the reasons we need constant food is because our body is dying. Luckily, it's also regenerating. Every week we get a new stomach lining. Every three years a new kidney. Every seven years an entire new body. The old cells die, the new ones come in, and this can only happens when we have a constant stream of atoms to supply the process.

Now, if we cut Wolverine in half and he wants to grow back the other half, what is that half going to be made of? Obviously, it has to be made of atoms, and rather more obviously, as a biological specimen, the atoms must be arranged into cellular structures. That happens through our metabolic processes.

But if you cut Wolverine in half, there'd be no way for him to process the atoms necessary to regenerate. He'd be stuck with whatever atoms he had left in his system, which wouldn't be enough to grow an entire new half of his body. Therefore, the short answer to "If you cut Wolverine in half, say with an adamantium sawmill, would each half regenerate into a full Wolverine?" is "No. Neither half would."

Despite Wolverine's awesome healing powers, neither the top nor the bottom could come into possession of the raw material needed to make the other. His mutant powers could only work if they have the supplies they need to get the job done.

Which reminds us that we're talking about a mutant here, so let's just give Wolverine the benefit of the doubt and say that he can take some material from his fat cells and use them to regenerate. That would mean that the fatter Wolverine is at the time of his cleaving, the more material he would have to build the parts necessary to process food. Also, we'll even give up all the muscle he has to spare, to shift these cells to create a factory to process raw materials: the gastro-intestinal tract.

Ignoring the possibility of infection, and the fact that he would need to divert precious resources towards fighting the infection, Wolverine would need to rebuild his missing colon, to process materials, and to a lesser extent, a bladder, just to expel waste.

(We'll be generous with the thermodynamics and assume that there is no waste, since we're recycling cells here.) Theoretically, Wolverine's top could be able to reorganize itself to the point that it can ingest protein again, take that material, build himself a waste system, and continue the process until the entire body is regenerated.

I mean, theoretically.

However, his bottom half has no such option. It would need to build not only the entire gastro-intestinal tract to process raw materials, but a circulation and respiratory system to deliver oxygen to its cells. A starfish limb can regenerate an entire new starfish because it has the necessary vital organs within it. Wolverine's ass does not.

BUT, since we're talking about comic books, let's say that hypothetically speaking, the bottom half manages to regenerate a top half. Would we then have two Wolverine's?

Not exactly. We'd have a Wolverine, the man, and we'd have his genetic clone.

The clone would have been built from the design information in the bottom half. But just as much as Lamarck was wrong for suggesting that it was giraffe stretching that led to their long necks, we'd be wrong to think that the Wolverine clone was Wolverine himself. This is a philosophical statement, but what makes Wolverine who he is, is how his experiences have altered/shaped/guided his nature. The Wolverine clone will not have any memories. No experiences. No knowledge. It will simply be a blank slate, since it's brain has been built.

One does not encode knowledge, wisdom, or experience into DNA.

More interestingly, when the clone Wolverine is built, how old is he? DNA doesn't encode age either, which makes it interesting to think what the clone would look like. As people age they acquire scar tissue all over their body. Scar tissue is resilient, that's why people have scars. But Wolverine is always portrayed as someone who doesn't have scars, even after having his face ripped apart by adamantium claws.

Is this a factor in why Wolverine is younger than he is? I would think so. His resiliency to age, then begs this question: When will Wolverine die?

The short answer is when his systems reach a state where they cannot deliver oxygen to his cells. In that case, his cells will eventually die without having a means to replace them. This can happen with extensive trauma.

But in terms of old age, if his cells are replaced without the accumulation of scar tissue, if his systems are regenerated just as good as ever, if his body resists the accumulation of scar tissue, then really, it seems like he could live "forever."

If you were to cut Wolverine in half, he'd probably die. But if you allow some minor miracles in the physical process, you might also have a Wolverine with his clone. It all depends on how far you're willing to bend the laws of physics.

Michael Zannettis is not a biologist, doctor, or zoologist, but he does play one at dinner parties. His book is not available in stores and may never be. He lives in Astoria, for free.

He then replied: “I was actually referring to if you cut him lengthwise such that you have left and right halves, rather than top or bottom halves.”

If the cleave was lengthwise instead of top-bottom, Wolverine has a much better chance of surviving. He would have to immediately create a sheathe to lock in any spilling materials. Let's assume, for the sake of argument, that the sheathe presents itself almost simultaneously with the incision. He is, after all, a mutant healer.

In that case, each half would have a lung. People do survive with "only" half a lung. Also, it'd have half a heart. He would therein have about eight to ten minutes to regrow the heart to the point that it could beat blood again. More if we want if we want to be liberal about Wolverine's healing powers to replace dead cells.

At the time of a cardiac arrest, the body does fine for several minutes because it already has the oxygen it needs. If an EMT were to artificially pump blood through the system, the body can survive for a couple more minutes, because the circulated blood is already saturated with oxygen.

That being said, I find it interesting to think whether we were to cleave Wolverine in half in a hospital operating room, for the specific purpose of making two of him, how'd we pull this off.

The most obvious first step would be to bypass the heart. We'd take the adamantium saw, cut into his chest cavity, remove his heart, and hook up his circulation system to a bypass machine. I don't think that Wolverine could handle a transplant heart, since his immune system is so strong that he'd probably kill it. From there, you'd cut the heart in half, and graph it to his body.

I'd hook him up to a respirator to breathe for him, a catheter to pee for him, and colon bag to poop for him, effectively taking care of his vital functions. The real problem is will Wolverine survive if we cut his brain in half?

The short answer is, of course not! But, then again, there are many, many people in this world who have had an entire hemisphere of their brains removed and have gone on to live healthy and normal lives. But to just rip into his brain with an adamantium saw would put Wolverine at major risk for edema, the swelling of the brain from trauma, and actually, stroke.
Moreover, the saw would cut in half his cerebellum, which controls sensory perception.

Since we're breathing and beating for him, I'm not concerned about that. What I am concerned about is his nervous system. Wovlerine's body somehow has to "know" that it's missing one half and that it should be working to heal it. For it to "know" requires an active nervous system. Not a conscious one, just a functional one.

Therefore, would a functional nervous system survive being cut in half. Assuming so (and why not, we are, after all, talking about the man who is "The Best He Is At What He Does") then Wolverine's body will immediately begin healing itself.

A staff of doctors might aid the process with blood transfusions, IV drips, and reconstructive surgeries. What does that all mean? Well, I guess in the right situation, under the right conditions, assuming a mutant healing factor with regenerative powers, and the stone-cold most bad-ass super hero to ever walk the Earth, then yes, if you cut Wolverine in half length-wise you will end up with two Wolverines (though not the same type since each would have lost the experiences and training of one half of their brains, but, you know, close enough.)

Michael Zannettis is not a doctor, nor in medical school, and has never taken, much less studied for the MCAT. In fact, he giggles when he hears the word 'orgo' because it sounds kind of dirty. As such, he is not qualified to give medical advice. However, he did use to drive an ambulance on a college campus, and so has seen lots of people drink way too much and vomit into red plastic bags--most of them weren't even patients!