"The estimated effective size of the founding population for the New World is about 70 individuals," Hey said. "Calculations also showed that this represents approximately 1 percent of the effective size of the estimated ancestral Asian population."
"Effective size" in population genetics is often thought of as the number of adults of reproductive age. One rule of thumb is the effective size might be about one third of the 'census population size' which, in this case, comes out to about 200 people.
In addition to population size, Hey's rigorous and complex methodology also generated historical estimates of when the divergence occurred. His dates are consistent with much of the archaeological record -- in the range of 12,000-14,000 years ago.
The full article will be published in the June edition of PLoS Biology. I can hardly wait!