Subjunctive

I've seen the use of the indicative instead of the subjunctive in British writers, but this doesn't seem to be common among Americans, especially in edited prose. David W. Anthony, in his book The Horse, the Wheel and Language, writes: First, for Proto-Indo-European to have remained a unified dialect chain for more than thirty-five hundred years, from 6500 to 30000 BCE, would require that all its dialects changed (instead of change) at about the same rate and that the rate was (instead of be) extremely low. The funny thing is that he uses the indicative with require earlier in the book, but I can't locate that page. I'll be on the lookout for other examples.