Yes, scientific studies have been done resulting in the theory that due to evolution, when a man knows or suspects his mate has been with another man, he becomes aroused in order to inseminate his mate with 'killer sperm' to kill off the other man's sperm thereby preventing inpregnation by him. This theory arose due to the discovery of 'killer sperm' and speculation as to why it had ever come into being. So, a conclusion based on this theory is that suspecting, knowing, or actually watching one's mate having sex is biologically very arousing for a man regardless of jealousy issues. It also implies that in order for the situation to have arisen in the first place, prehistoric women had to have regularly had at least two sex partners, one that they were committed to and at least one other that they cheated with. So, modern swinging and open marriages may be seen by some as being an 'evolved' way of dealing with a human social-biological reality.