**Core Concept**
Atavism refers to the phenomenon where an offspring exhibits a trait or characteristic that is not present in either parent, but is inherited from a more distant ancestor. This occurs due to the expression of a recessive gene that was previously masked by a dominant gene in the parent's lineage.

**Why the Correct Answer is Right**
Atavism is a result of the re-emergence of a recessive gene that was previously present in a more distant ancestor, but was overpowered by a dominant gene in the parent's lineage. This can happen when an individual inherits two copies of the recessive gene, one from each parent, or when the dominant gene is not expressed due to a genetic mutation. In the case of atavism, the child exhibits a characteristic that is not present in either parent, but is a throwback to a more distant ancestor.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the concept of atavism.
* **Option B:** This option is incorrect because atavism does not refer to the resemblance between twins.
* **Option C:** This option is incorrect because atavism does not refer to the resemblance between parents and children due to genetic similarity.

**Clinical Pearl / High-Yield Fact**
Atavism is an important concept in genetics, highlighting the complex interplay between dominant and recessive genes in determining an individual's traits.

**Correct Answer:** D.