According to this
Humans, like other warm-blooded animals, expend a lot of energy and need a lot of oxygen. Our four-chambered hearts make this possible. It gives us an evolutionary advantage: We're able to roam, hunt and hide even in the cold of night, or the chill of winter.
But in the other hand, there are heartless JellyFish of 2.3 meters with up to 70-150 tentacles per one of each 8 lobes of up to 37 meters in lenght. Lion's mane JellyFish
Having humans spending a lot of their energies in moving limbs, even though I understand JellyFish move in another environment, I'm having a hard time believing moving our limbs spend more energy than moving 70-150 tentacles per one of each 8 lobes of up to 37 meters in lenght.
What's the evolutionary purpose of having hearts? Is it for animals with it to be able to expend more energy or is there any other reason for it?