And I argue that “conception” occurs exactly when we all learned it did in science class.
When the sperm fertilized the egg - they both lose the DNA identity of their hosts, and a new DNA code is formed. That is because a new life has formed. Left alone - in the body - where conception has occurred for millenia (up until recently), this new life will either implant and continue to grow or it will not.
That some of these embryos will not survive that process does not mean that our lives did not begin at the moment of “conception”
Not sure what you mean by “lose the DNA identity of their hosts”.
A sperm or egg cell is produced by meiosis. The original cell has the DNA of the person, one of each chromosome from mom and one of each from dad. This is mixed up so the NEW resulting DNA pattern in the reproductive cell is unique to that cell, and that cell will only have HALF the DNA of the parent cell.
When the sperm and the egg combine each half forms a new whole - but nothing happens with the DNA other than that it is combined with the ‘missing’ half.
The sperm cell is alive, the egg is alive - both have the DNA of the parent - but in a new configuration.