Aristotle created the first animal classification system over 2,300 years ago

In 350 BCE, Aristotle authored 'History of Animals,' the first systematic attempt to classify the natural world. He categorized creatures into two primary groups: enaima (animals with red blood, such as mammals and birds) and anaima (bloodless animals, such as insects and mollusks). This division closely mirrors the modern distinction between vertebrates and invertebrates. Aristotle even puzzled over sponges, correctly identifying them as animals due to their ability to contract, despite their lack of visible movement.