And the "they" in question is Warren Buffet, https://nymag.com/intelligencer/2009/06/you_cant_make_a_baby...
> Brooks points out this limited divisibility with another example: while it takes one woman nine months to make one baby, "nine women can't make a baby in one month".
taking the population of the earth and the birth rate and doing some math, you get around to needing 12,000 women of reproductive age for you to have a baby tomorrow.
12,000 is a lot of women! it's well above Dunbar's number. think about that, next time the 9 women one month baby topic comes up.