Here is a link to a new paper by Steven Andrew Jacobs. The paper defends the view that there is “a large and robust scientific consensus” that a human’s life begins at fertilization.
The author doesn’t take a position on the normative issues. Jacobs states: “This paper does not argue that the finding ‘a fetus is biologically classified as a human at fertilization’ necessitates the position ‘a fetus ought to be considered a person worthy of legal consideration’. The descriptive view does not dictate normative views on whether a fetus has rights, whether a fetus’ possible rights outweigh a woman’s reproductive rights, or whether a fetus deserves legal protection. However, presenting this view to Americans could facilitate such discussion. Resolving the factual dispute on ‘when life begins’ with biologists’ descriptive view could help parties focus on policy discussions related to the important ethical and legal issues of the U.S. abortion debate.”