What is the first organism to develop a heart?

The first organisms believed to have developed a heart-like structure are thought to be early vertebrates, specifically within the group of jawless fish known as agnathans, which emerged over 500 million years ago. These primitive hearts were simple muscular tubes that pumped blood, evolving over time into the more complex structures seen in modern vertebrates. The development of the heart was crucial for efficient circulation, supporting increased metabolic demands as organisms became larger and more active.