Re: What if humans had exoskeletons?

Hi Anubis,

I would like you to perform the following experiment:

1) Find two pieces of paper

2) With the first piece, cut it down to a long strip that is 5cm wide. Roll it into a long cylinder and use a piece of tape to hold it all together. You should have a cylinder about 1.6cm wide.

3) Take the second piece and roll it into a cylinder that is about 7cm wide.

Both cylinders should have the same thickness equal to one sheet of paper.

4) Now, holding each cylinder in your hands, blow firmly on each cylinder.

You should find that the larger cylinder deforms while the smaller cylinder is able to hold its shape. Exoskeletons are great for small animals such as insects because they are thin, light and hold their shape well.

If a large animal such as a human being had a thin light exoskeleton, there would be several problems. Since the exoskeleton would not be able to hold its shape, it would be difficult to keep the vital organs protected and the organism would be subject to damaging levels of stress just by moving around.

If you take 4 sheets of paper and roll them up into a cylinder 7cm wide, you will find that the cylinder was able to hold its shape. A large animal would need a thick exoskeleton in order to provide the minimum level of support and protection. Such an exoskeleton would be heavy and additional mass would be required in the form of extremely huge muscles.

An organism's ability to survive depends on whether it can meet its energy requirements. A heavy body would have high energy requirements and an organism's ability to find enough food would be hampered by its own mass.

The largest crabs do reach nearly 2m across, but they are aquatic organisms supported by water and have a low metabolism.

A large terrestrial organism with an exoskeleton would experience problems with gas exchange and growth. Exoskeleton is not living material that can divide and grow. An insect has to discard its exoskeleton every so often until it reaches full size. During this time, its body is soft and vulnerable. An insect is limited in how much it can grow during molts and must molt several times to reach maturity (the range is actually 2-50 times, but most insects have between 5 and 11 instars. Therefore, we would have to molt hundreds or thousands of times just to reach our size.

Personally, I am glad we have out internal skeletons as they serve us very well.

Thanks for your interesting question

Richard Kingsley