What is the function of appendix in verte brates? Why did it become vestigial in modern man?

Explanation

### Step-by-Step Solution:

1. **Understanding the Appendix**: The appendix is a small, tube-like structure attached to the large intestine in vertebrates, including humans. In ancestral vertebrates, it played a significant role in digestion.

2. **Function of the Appendix in Vertebrates**: In early vertebrates and ancestral humans, the appendix was involved in the digestion of cellulose. These organisms consumed a diet rich in plant material, which contains cellulose that is difficult to digest. The appendix helped in breaking down this cellulose, aiding in nutrient absorption.

3. **Dietary Changes Over Time**: As human diets evolved, particularly with the advent of cooking, the consumption of raw, fibrous plant material decreased. Cooking food makes it easier to digest, breaking down cellulose into simpler sugars that do not require the same digestive processes.

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