Pretty sure giraffes have 2 hearts, I think the brachiosaurus also had 2 hearts too. I have a feeling there was a fish or other ocean creature with multiple hearts and maybe another mammal?
Heres some info I found real quick. No giraffe, several sea creatures, a couple land animals, one dino maybe, and some vague ambiguity.
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I understand the concern, but I see it as more redundancy, like kidneys. If 1 heart gives out, you have a spare, and considering that we only have 1 that can do its job for 100+ years i dont see complexity as being an issue.
Also Im just here to advocate the theoretical that you could have 2 hearts with no issues, rather than it being something completely impossible.
The heart is a really simple contraption. The heart is broken down into 2 halves, and 2 more halves after that, for a total of 4 parts.
Focusing on one half, what most people would recognize as “the heart” and what it does. Blood enters the heart into a mini pump, that pump pushes blood into a second pump, making it a little extra full, so when that pump decides to squeeze, you get extra force leaving it to send blood to the rest of the body and back to the other half of the heart later.
Imagine filling a water balloon with half way some water and squeezing it out. It doesnt have as much “umph” as if you filled that same water balloon nearly to its popping point and squeezing.
The other half of the heart is the exact same, just weaker as it only sends blood a short distance to your lungs and back to the big half of the heart. Thats it, thats all the heart does. 2 pumps that load up the other 2 pumps with blood to be shot out to the rest of the body.
Sometimes things go wrong, youve very likely felt a small heart spasm before, but the heart is a mostly self correcting, fully autonomous system. I cannot see why adding in a 2nd heart would be a detriment, just makes blood go round and round more often.
I spent a few years studying as an EMT and Medical Assistant and I think I loved the circulatory system the most. However, Im no doctor and I simplified the heart a bit because I dont think needing to understand everything adds to the theoretical discussion of 2 hearts
Adequately pressurized doesnt seem like a problem here, over pressurization does seem like an issue, the body is very good at self regulation.
If you had 2 hearts, i can imagine each heart only needing to work half as hard to keep a person alive, except for times when the blood vessels themselves become “unnaturally” over pressurized, such as the case of regularly high blood pressure, then both hearts have to work harder, regardless of how many hearts you have.
I dont theoretically see an issue with 2 hearts
“Wait, Alfiria can join up? Oh my god shes cool! I wonder why she wasnt on the wiki of characters able to join your party?”
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I agree with what youre saying completely, Im just saying i theoretically could see how you could live with 2 hearts, not the efficiencies, intricacies, or failures of having 2.