Current studies of rate of genetic drift (how quickly non-essential DNA changes occur) suggest that, studying mitochondrial DNA, the funnel’s narrow end, i.e. one copy, was 225 to 250 thousand years ago. Eve, in other words. That’s around the same time that all major mammalian species went through a ‘survival funnel’ or in other words came close to dying out. Must have been a VERY hard time all around.
For a man’s Y chromosome, a small collection exists in a remote part of Africa which looks 400 thousand years old, but everywhere else the funnel’s narrow end happened 75 thousand years ago, give or take a few. In short, Adam.
Genesis 1 reads much more like liturgy than history or science. In fact Genesis 2 contains, if you look closely, an alternate liturgy with fewer days and a different sequence. As a Christian, I read Genesis 1:3 “And God said, ‘Let there be light,’” as the one accurate piece of history / science, i.e. that He said so 13.8 billion years ago. The first few verses of the Gospel of John lead to the idea that Jesus was that Word, who made all things that were made, i.e. Jesus held the active role in the Godhead.
Since then the knowable universe has unfolded into two hundred sextillion stars (a 2 followed by twenty-three 0’s) so any effort to cram His self-revelation, enshrine His own private OED, into a handful of verses given to his Chosen People several thousand years ago, and ditto any effort to cram the creation of the vast universe into Day One six thousand years ago, is pitiable and insulting.
God is patient and merciful, so trying to boil Him down to the constraints of His original Deed of Title in Genesis is what it is. We are humans and our actions are always imperfect. For all your committed Young Earth and Creation Science acquaintances, just let them be; they’re not capable of harming God. Think of it this way, in fact – Jesus wants every believer to come to Him with a child’s trust, and they at least have that. Now – do you or I? Huh?