“In various places we have defended the position that a new human organism, that is, an individual member of the human species, comes to be at fertilization, the union of the spermatozoon and the oocyte.” 100
100 Lee P, Tollefsen C, George RP. The ontological status of embryos: a reply to Jason Morris. J Med Philos. 2014 Oct;39(5):483-504, PMID: 25223411, https://pubmed.ncbi.nlm.nih.gov/25223411.