Missing out on marriage is a big loss of status. By your reasoning, one then seeks to find a way, any way, to regain status. You can't find it in marriage (in t

Missing out on marriage is a big loss of status. By your reasoning, one then seeks to find a way, any way, to regain status. You can't find it in marriage (in the short term), so you try to find it some other way. You take bigger risks, which may include battle and violence. In general, people in the bottom rung of status "classes" take bigger risks because they have less to lose. It makes sense that evolution would result in such beings taking bigger gambles, which can result in societal chaos in modern societies. If you have a reasonable chance of reproducing as things are, you tend to play it safe. If don't, then then playing it safe is not a good numerical strategy. If somebody's chance of reproducing is say 2%, they may start to think, "Hey, if me and a bunch of other losers invade the next town, my chance of "getting some" goes up to 5%." The math of evolution would favor such behavior. You see it in sports also: if your team is are clearly losing, you gamble more with "tricky" plays and perhaps cheating, which may result in interceptions (losing possession of the ball) and/or penalties. I should point out this is probably a factor with any inequality, not just marriage. Pitchforks come out when enough feel left behind.