If that makes sense, then why haven't women ever been allowed to take multiple husbands in locations and times where men have outnumbered women, as was often the case in the West on the US Frontier, in Texas both when it was part of Mexico and during its days as a Republic, in Australia during its early settlement? Only in a movie, Paint Your Wagon.
Because in the example the guy gave me it was after
centuries of war...not a gold rush or something else that was carried out by choice by a culture that already had most of it's ground rules in place...and be honest, the need to boost your population would
not be best served by the 1 woman + multiple men method would it?
As for your friend's explanation, that's just another version of the old wives tale, which is actually circulated by old husbands, that a woman isn't fulfilled without a husband and kids. If he's worried about lonely women in need of love, than he should encourage lesbianism as well as polygamy.
Because gay people in those days could not reproduce...and it was about boosting your population in those days...I ain't talking about last week here...I'm talking hundreds and hundreds and hundreds of years ago...when their cultures where at the formative stages!
For these cultures, poligamy was not about getting their rocks off or some perveted thing...it was simply survival...and they survived that way...