**Core Concept**
Clubbing is a clinical sign characterized by changes in the shape and structure of the fingers and toes, often associated with underlying pathological conditions such as lung disease, heart disease, and cancer. The earliest evidence of clubbing is typically observed in the distal phalanges of the fingers.

**Why the Correct Answer is Right**
The earliest evidence of clubbing is usually seen in the distal phalanges of the fingers, where the soft tissue and bony changes are most pronounced. This is due to the increased vascularity and edema in the nail bed and surrounding tissue, which leads to the characteristic clubbing deformity. The distal phalanges are more susceptible to these changes because of their relatively thin bone structure and rich vascular supply.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because clubbing can occur in the proximal phalanges, but it is less common and typically represents a more advanced stage of the disease.
**Option B:** This option is incorrect because clubbing is not typically seen in the metacarpophalangeal joints, which are more commonly affected by conditions such as rheumatoid arthritis.
**Option C:** This option is incorrect because while clubbing can occur in the toes, it is less common than in the fingers and may be associated with different underlying conditions.

**Clinical Pearl / High-Yield Fact**
The earliest evidence of clubbing can often be detected by inspecting the nail bed and surrounding tissue for signs of increased vascularity and edema. This can be done by gently pressing on the nail bed with a finger, which will cause blanching of the nail if there is increased vascularity.

**Correct Answer:** D. Distal phalanges.