According to fossil evidence, when did life on Earth first arise?

• A. About 500 million years ago
• B. Around 4,000 years ago
• C. Approximately 3.5 billion years ago
• D. Roughly 65 million years ago

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the context of the question, which is asking about the origin of life on Earth based on fossil evidence. Fossil evidence provides clues about the earliest forms of life preserved in rocks.
2. Step 2: Recall that the earliest known fossils are stromatolites, which are layered structures formed by the activity of ancient microbial life, specifically cyanobacteria. These fossils date back billions of years.
3. Step 3: Recognize that the timeline of Earth's history is divided into eons, eras, and periods. The origin of life is associated with the Archean Eon, which began approximately 4 billion years ago.
4. Step 4: Note that scientific studies have determined that the earliest evidence of life, based on fossilized microbial mats and chemical signatures, dates to approximately 3.5 billion years ago.
5. Step 5: Eliminate incorrect options by comparing them to the timeline of Earth's history. For example, 500 million years ago corresponds to the Cambrian Explosion, not the origin of life, and 65 million years ago marks the extinction of dinosaurs, not the emergence of life.