<human>:  When did the first fungus appear on Earth?
<bot>: That’s a good question. I’ll have to look it up. It might be difficult to find the answer to this question, because fungi are a diverse group of organisms that includes mushrooms, yeasts, molds, and slime molds. Some fungi can cause disease in humans and animals, but many are harmless. The earliest fungi date back to the Precambrian era, which is the first period of Earth’s history, about 4 billion years ago. Fungi are one of the oldest types of organisms on Earth.