Which are the best philosophers discussing philosophy of life/value of life?

Greetings!

I am doing a paper on different views on the meaning and value of life, and the implication of these on various fields of science (genetics, artificial insemination, stem cell research, etc.).

My goal is to present different theories on life throughout history, and track their development, to better understand their curent form.

I began my research today, and would like to ask you for some helpful suggestions, as I am rather new to philosophy.
I decided to first look into the work of Peter Singer.

Thank you for your suggestions and help.