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ThomasEdmund84 t1_j9rzc2q wrote

> EDIT: To piggyback this logic, why don't we have more 'spares' of other organs. Why is the redundancy factor only built into kidneys?

Its likely to do with trade-offs between the resources the human body needs to grow and maintain vital organs and also how feasible having redundancy is.

e.g. lungs are perhaps semi-redundant, obviously having one lung = much reduce physical capacity and isn't great, but we do have two.

My physics might be a little off - but I think its counter productive to have two hearts? Human digestive system already has lots of failures in its complex system so doubling up would probably mean more room for errors.

Two brains? Forget about it.

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AtrioventricularVenn t1_j9tlu18 wrote

We do have two hearts, one for venous (low pressure) flow and one for arterial (high pressure) flow. Also, each "heart" has its own secondary pump as an additional failsafe mechanism. This is the reason why heart defects or acquired issues can go undiagnosed for several years while the individual still maintains a healthy function.

You can argue that you have at least 3 brains: left and right hemispheres, and the cerebellum. Specialization gives these 3 structures functions and architectures that blur their independence from their counterparts. Damage to any of these structures can be compensated by the others but, of course, the level of compensation varies between individuals and age.

The digestive system is a completely different story because of how embryonic development works. We (and most animals) develop around a whole that becomes our single digestive tube (or tract). We are basically worms with funny looking appendages with wiggly tiny tentacles at their ends.

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