What issue has dominated much work in lifespan development? how much of people's behavior is due to their genetically determined nature and how much is due to nurture? what are the historical roots of developmentalists and life span development? how are developmental research studies developed? which area(s) of lifespan development are the most important?

In lifespan development, there is an important question which tries to explain the concept. The question discusses that our existence-being is due to genetics or it is due to environment and culture, respectively known as nature and nurture. We know that all human beings carry some sets of genetic codes. But, our environment and culture also play a role in the development process. There is a reciprocal interaction between two concepts. How much they contribute to the development process is still debatable.
 
The correct How much of people's behavior is due to their genetically determined nature and how much is due to nurture?