Presence of tail and coarse hair in human baby is

Options

A. Radiation
B. Atavism
C. Mutation
D. Crossing - over

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the presence of a tail and coarse hair in a human baby and what this phenomenon is called among the options provided: radiation, atavism, mutation, or crossover.

2. **Defining Atavism**: Atavism refers to the reappearance of a trait or characteristic in an organism that was present in its ancestors but has been absent in more recent generations. This can happen after a long period of non-existence of that trait.

3. **Identifying the Phenomenon**: The presence of a tail and coarse hair in a human baby is an example of atavism because these traits were likely present in human ancestors but have since disappeared in most modern humans.

4. **Eliminating Other Options**:
- **Radiation**: This term refers to the adaptation of a single species to different environments, leading to various traits, which does not apply here.
- **Mutation**: This involves changes at the genetic level, which is not the case for the traits mentioned in the question.
- **Crossover**: This occurs during meiosis and involves the exchange of genetic material between chromosomes, which is unrelated to the presence of these traits.

5. **Conclusion**: Since the presence of a tail and coarse hair in a human baby is a re-emergence of ancestral traits, the correct answer is **Atavism**.

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