While the line drawing fallacy certainly comes into play here, one can with some confidence say that /before a single neuron is formed/ is most certainly a safe spot to point at and say “not yet.”

I didn't quickly find a definitive answer about the time the first neuron forms, but some brief searching around seems to indicate the neurons are already assembling into complex structures before 5 weeks.

So it seems like development of the first neuron would be well before that, and not a very practically-useful line.

https://en.m.wikipedia.org/wiki/Development_of_the_human_bra...

The mother.

Until what age? Birth? 1 year old? 18? 80?