Let’s imagine that organs can be perfectly grown in a lab and installed into a body without any chance of rejection or other complications usually associated with organ transplant.
You, a perfectly healthy adult human, go to the doctor and have them put a second heart in your chest that is connected to the circulatory system with your original heart.
What would be the effects of this? Could it even be done in this hypothetical situation at all?
Giraffes are mammals and only have 1 heart. It’s freaking huge, though, at 11 kilos.
octopus and cuddlefish and similar frequently have multiple “hearts” but they’re not the same as mammalian hearts. Briachiosaurus probably had an even larger heart than a giraffe, but it was still a singular, 4 chambered hear.