Which of the following is not a vestigial organ ?

Options

A. Presence of tail newly born human baby
B. Wisdom teeth of human
C. Appendix of human
D. Hind limb bones and pelvic girdle in Python and whale

Answer

To determine which of the following is not a vestigial organ, we need to analyze each option provided:

1. **Presence of tail in a newly born human body**: This is an example of atavism, which is the reappearance of a trait from ancestral lineage. It does not represent a vestigial organ because it is not a remnant of a lost function but rather a reversion to an ancestral trait.

2. **Wisdom teeth of humans**: These are considered vestigial organs. They were once useful for our ancestors who had a different diet that required more chewing power. In modern humans, they often cause dental issues and are frequently removed.

3. **Appendix of humans**: The appendix is also considered a vestigial organ. It is a remnant of a larger cecum that was used by our herbivorous ancestors for digesting cellulose.

4. **Hind limb bones and pelvic girdle in python and whale**: These are vestigial structures as well. They are remnants of limbs that were once functional in their ancestors but have lost their original purpose in these modern species.

Based on this analysis, the option that is not a vestigial organ is:

**Correct Answer: Presence of tail in newly born human body (Option 1)**

### Step-by-Step Solution:
1. **Identify the options**: List the given options to analyze each one.
2. **Define vestigial organs**: Understand what vestigial organs are—remnants of structures that had a function in ancestors but no longer serve a purpose.
3. **Analyze each option**:
- Option 1: Presence of tail in newborns is atavism, not vestigial.
- Option 2: Wisdom teeth are vestigial.
- Option 3: Appendix is vestigial.
- Option 4: Hind limb bones in python and whale are vestigial.
4. **Determine the correct answer**: Identify which option does not fit the definition of a vestigial organ.