What would be the consequences of these biological changes to a human

Question

So let's say you changed a human's DNA to give him:

• a thick exoskeleton that is a lot like that of a mantis shrimp (to make him bullet-proof)
• very small holes all over his body to use to breathe instead of a nose (to make it hard to cut off his oxygen)
• a lot of stem cells stored in his bone marrow (to quickly repair damage)
• the DNA repair mechanisms of Deinococcus radiodurans (to protect him from radiation damage)

What would be the toll on such people with this genetic change, like how much would their caloric intake go up and what kind of special food would they require to maintain this body?

Answer 1

The consequence would be he stops being a very functional human. Having all these things will make for a very problematic disability.

a thick exoskeleton that is a lot like that of a mantis shrimp (to make him bullet-proof)

Bullets probably won't hurt him but larger calibers will probably still do. Although I think he would have problems moving around with a heavy shell like that. Also shells don't protect against shock so internal damage will happen even if the shell if undamaged.

very small holes all over his body to use to breathe instead of a nose (to make it hard to cut off his oxygen)

This kind of breathing is likely less efficient than just having a central system like the nose and lungs. Arthropods have a problem growing very large in real life and this is one of the reason why they might be limited. Back when the Earth was more oxygenated and there was less competition from other animals was when large arthropods existed.

have a lot of stem cells stored in his bone marrow (to quickly repair damage) have the DNA repair mechanisms of Deinococcus radiodurans (to protect him from radiation damage)

Bacterial DNA repair would probably not work very well in humans. From what I am reading, Deinococcus Radioduran keeps 2 copies of DNA and have mechanisms to repair any damages within hours but it has a much smaller genome compared to a human and it's repairs are still susceptible to failure like during normal cell operations. What I imagine happening would be cancer cells developing from his cells being extremely resistant to chemotherapy. Can you imagine self repairing cancer cells that is resistant to chemo? The stem cells might be nice to have tho but I don't know if it will help this guy with much.

At the end of the day, I don't see this person functioning very well as a human. I think it would be very hard for this person to do anything or go anywhere, not only would it be hard to move in his large shell but it would be hard for him to use any vehicles. It might even cost a lot of money to keep him alive because of this disability. Not being able to breathe well and having such an unusual body would require specialized medical attention, I imagine he would need a very highly oxygenated room as well as a specialize bed.

As for food. I guess the hospital might need to make sure he gets more protein than the average person as DNA repairs going on the background might need more protein. Maybe he would need more other nutriments to supplement his shell as well. I'm not sure what kind of exercise plan they can give him because moving can cause server internal bruising and using too much energy with the limited oxygen he can access to can cause serious problems. I guess keeping him completely still might be best for him. In this case it would probably mean limiting his calorie intake as well.

Answer 2

Humans and related vertebrates breathe by changing the size of our thoracic cavity using muscular action. Making the cavity bigger reduces interior pressure and air flows in to the chest (and lungs). Making the cavity smaller increases interior pressure and air flows out.

If you replace the thorax with a rigid structure you will not be able to change its shape. You will have no way to pull air in or push air out.

You could work around this by making the exoskeleton jointed. Dragonfly nymphs do this with their abdomen, and by changing the size of the abdomen they can breathe by pulling water into and out of their rectum.

http://noticing.co/the-thrill-of-the-gill/

Having gills inside (rather than outside) the body gives the dragonfly nymph a few terrific advantages. Not only does it attract fresh oxygen, there’s a totally neat side-effect – jet propulsion!

By squeezing water out of its butt, the dragonfly nymph can propel itself in the opposite direction, rocketing itself safely out of harm’s way, or launching it towards its lunch (hooray for Newton’s third law). As far as we know, dragonfly nymphs are unique among insects in this ability

So you could work something like this with the many spiracled thorax and keep the fundamentally human lung and gas exchange apparatus. But instead, I strongly suggest you model your engineered human entirely on the dragonfly larva, thus obtaining the propulsion ability as well.

Answer 3

I second A. C. A. C. on the issue that having trachea instead of lungs won't work. If it would, insects would rule the world. So you need some active breathing to suck air using all these scattered holes. Hard.

Another issue is that exoskeleton is not called skeleton for nothing. You need to attach muscles to it, you'd need basically to invert all the "mechanics" of human anatomy.

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Your idea was probably just developing a more rigid and ruggedised skin. Well, one could plate the skin with something similar to teeth enamel. In the standard human we have a huge problem: at least some of the tooth tissues have lost their progenitor cells, so there is no way to a human outside of prenatal phase to grow more teeth.

In a similar manner, it could be a problem if a part of the skin-enamel is shattered. I sense there a story potential. Of course, your fellow DNA-designer would get back to drawing board an let those humans+ keep their progenitor cells for enamel. Would also help with caries.

But there is a bigger issue. Skins does huge work in temperature regulation, sweet dissipation, there is also a sensory contribution. All this is lost underneath an enamel shell. You humans+ would need to sweat like dogs do.