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Why do ribs have spaces between them? (self.askbiologists)

submitted 1 year ago by TheSmartDude to c/askbiologists

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Anyone who knows how a skeleton looks like knows that there are spaces between the ribs. However, why does it have gaps between them? Why isn't it a single shell?

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[–] [email protected] 12 points 1 year ago (1 children)

The gaps between each rib allow you to curve your chest. If it was a solid shell, you’d be forced to keep your chest perfectly straight, which would impact mobility. Evolutionary pressures preferred mobility over a “shell-like” protection.

[–] [email protected] 1 points 1 year ago* (last edited 1 year ago)

Having a shell like protection wasn’t that necessary in most cases. Turtles needed the protection, but mammals have been doing just fine without it. Probably the flexibility helps too.

Shells are also heavy. If an deer had a shell, it wouldn’t be as fast. Also, the shell wouldn’t really help agains wolves, so that protection would come with a lot of downsides. I guess the only real benefit would be when humans are trying to stab the chest or sides of the deer with spears and arrows.