Step 1: Understanding the Concept:
Neo-Darwinism, also known as the modern evolutionary synthesis, is the fusion of Charles Darwin's theory of evolution by natural selection with Gregor Mendel's principles of genetics. The question asks to identify the key figures who laid the mathematical and theoretical groundwork for this synthesis in the early 20th century, founding the field of population genetics.
Step 2: Detailed Explanation:
- A. R.A. Fisher, B. Sewall Wright, and D. J.B.S. Haldane are universally recognized as the three principal founders of theoretical population genetics. Working largely independently in the 1920s and 1930s, they developed the mathematical framework to show how Mendelian inheritance and natural selection could work together to produce evolutionary change.
- C. Gregor Mendel was the 19th-century pioneer who discovered the basic principles of heredity. His work was essential for the modern synthesis, but he lived and worked long before the synthesis occurred and was not one of its architects. Neo-Darwinism is the integration of his work with Darwin's, a task carried out by later scientists.
Step 3: Final Answer:
The founders of theoretical population genetics and developers of neo-Darwinism are R.A. Fisher, Sewall Wright, and J.B.S. Haldane. Thus, the correct option includes A, B, and D.