Question

Which one of the following processes emerged earliest during the course of evolution?

• A. Antigen presentation
• B. Antibody production
• C. Phagocytosis
• D. Thymic education

Hint:

Phagocytosis is an ancient mechanism found even in amoebae — it represents the evolutionary origin of innate immunity.

Answer 1

The Correct Option is C

Step 1: Understand evolutionary immunology.
The immune system evolved from simple defense mechanisms in unicellular organisms to complex adaptive immunity in vertebrates.
Step 2: Trace the timeline.
- Phagocytosis originated in unicellular eukaryotes as a feeding and defense mechanism — thus predating multicellular immunity.
- Antigen presentation and thymic education are features of the adaptive immune system, which appeared later in vertebrates.
- Antibody production also evolved later as a hallmark of adaptive immunity in jawed vertebrates.
Step 3: Conclusion.
Therefore, the earliest immune-related process to evolve was phagocytosis.