Human life begins at fertilization, the moment when the sperm cell of the male meets the ovum of the female, resulting in a fertilized egg or zygote. This is when a new, genetically distinct human being has begun. Human embryologists and the majority of scientific evidence support the view that the embryo is a human being immediately from fertilization, possessing its entire genetic makeup and the potential to develop into a mature human being. There is consensus among many biologists that human life starts at this fertilization stage, rejecting ideas of a "pre-embryo" or gradual emergence of human life later on. The zygote is not merely a potential human but an actual human individual at this earliest stage in development.
While philosophical, ethical, and legal considerations vary with regard to personhood or the rights attached to this life stage, the biological start of human life is recognized at fertilization. Other perspectives sometimes consider later developmental milestones such as the appearance of the primitive streak at about 14 days post-fertilization or fetal movement, but scientifically the start of organismal human life is at fertilization.
