I did a statistical analysis and you are correct. The issue seems to be that crude birth rates from around 500CE and earlier are overestimated significantly. The bad source seems to be Kaneda & Haub, "How Many People Have Ever Lived on Earth?", where they assume a flat crude birth rate of 80 for all BCE dates. The probability distribution is just a function of pop and CBR, so it results in significantly decreasing modern birth probabilities.

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fxd an hour ago | parent | next [-]

In other words, the Flat Birth Theory.

We can call them flat birthers

	▲	karim79 an hour ago \| parent [-]
		Come on now. We all know the birth is not flat. It can be clearly seen from space.

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mmmnnn an hour ago | parent | prev [-]

https://www.youtube.com/watch?v=KKpILoUMMb8