That's very interesting, thank you for the context. I imagine I learned some amount of this long ago and have lost it to disuse. I also think I agree with the

That's very interesting, thank you for the context. I imagine I learned some amount of this long ago and have lost it to disuse. I also think I agree with the majority of your analysis after reading your references as well as [1] and [2]. And I apologize for my uninformed quoting of a line from the article and appreciate the education. I found [2] particularly informative because it outlines a multi-stage process through which an embryo goes, the earliest of which is fertilization as you described. My reading in the article, and perhaps relying too much on the artwork, seems to put the process described there at stage 1b-1c since the pronuclei looks to be in the process of fusing. My conclusion in cross-referencing [1] is that your "embryo proper" is around stage 4-5 and would have been implanted? > They're removing the pro-nuclei before they fuse (which is when a new human, specifically their first sovereign cell and their DNA, would be formed). I wish I'd had the context to appreciate this before my earlier reply. :) I also enjoyed reading parts of [3] and imagine there is probably better information nearly 60 years later. [1] https://en.wikipedia.org/wiki/Human_embryonic_development https://en.wikipedia.org/wiki/Human_embryonic_development [2] https://en.wikipedia.org/wiki/Carnegie_stages https://en.wikipedia.org/wiki/Carnegie_stages [3] https://publicationsonline.carnegiescience.edu/publications_online/developmental_stages.pdf https://publicationsonline.carnegiescience.edu/publications_...