Why do pelicans and humans require a more complex heart?

Pelicans and humans require a more complex heart to efficiently support their active lifestyles and meet the high metabolic demands of their bodies. A four-chambered heart allows for the separation of oxygenated and deoxygenated blood, ensuring that tissues receive a constant supply of oxygen-rich blood. This efficiency is crucial for activities such as flying in pelicans and maintaining energy levels in humans. Additionally, a more complex heart facilitates better regulation of blood flow and pressure, which is essential for both species' survival and adaptation to their environments.