Origin of first mammals occurred `:`

Options

A. 500 million yrs
B. 220 million yrs
C. 1600 million yrs
D. Over 1600 million yrs ago.

Answer

**Step-by-Step Solution:**

1. **Identify the Time Period of Mammal Origin**:
- The first mammals originated during the Triassic period.

2. **Define the Triassic Period**:
- The Triassic period lasted from approximately 250 million years ago to 201 million years ago.

3. **Determine the End of the Triassic Period**:
- The end of the Triassic period is around 200 million years ago.

4. **Analyze the Given Options**:
- The options provided are:
- 500 million years ago
- 220 million years ago
- 1600 million years ago
- Over 1600 million years ago

5. **Evaluate Each Option**:
- **500 million years ago**: This is too early and does not correspond to the Triassic period.
- **220 million years ago**: This is close to the end of the Triassic period and is a potential correct answer.
- **1600 million years ago**: This is far too early and does not relate to the origin of mammals.
- **Over 1600 million years ago**: This is also incorrect as it predates the Triassic period.

6. **Select the Correct Answer**:
- The correct answer is **220 million years ago**, as it is the closest to the end of the Triassic period when the first mammals evolved.

**Final Answer**: The origin of the first mammals occurred **220 million years ago**.

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