How many people would it take to bring in a new baby today?

Averaged out over human history, a generation is likely to have lasted for something like a quarter to a third of a century. Now decide upon a suitable definition of people for your purposes. If you limit that to members of the species Homo sapiens, then you're restricting yourself to the generations going back for something like 150000 - 200000 years. Should you prefer to include all members of the genus of Homo as people, then it's more like 2.5 million years.

Work out the number of centuries appropriate for your selected definition (or for both options), and multiply those by four and then independently again by three. The answer's likely to be somewhere between the two.

Update

"About 50,000 years ago Homo Sapiens came about."

The fossil evidence for the species is at least three times earlier than that. That's getting near to the time when the species first arrived in Europe.

One. A new baby or human would have to be created, ne dna and stuff.

That is like god stuff or whatever you may prefer to believe or not believe.

About 50,000 years ago Homo Sapiens came about. If we assume an average of 27 years per generation, that's about 1852 generations. The number of people in each generation doubles, so it'd take

∑{n=1,1852} 2ⁿ ≈ 6.43549 * 10⁵⁵⁷

which is an absolutely enormous number.

what do you mean?

500