Why do humans and animals have two nostrils?

Humans and animals have two nostrils to enhance the sense of smell and improve respiratory efficiency. Having two nostrils allows for better detection of odor direction, helping to locate food, predators, or mates. Additionally, it helps maintain airflow and oxygen intake, as one nostril can serve as a backup if the other is blocked. This bilateral structure also contributes to a more nuanced perception of scents.