TL:DR Science confirms what we all already know. Men prefer new women, as many as we can get.

Before we start it will be helpful to know exactly what Sperm Competition means.

Especially: "Some males, instead of or in addition to their own mechanisms of sperm competition, will guard their female partners from more copulation even after sperm deposition." (Aka human males, we all know that feel.)

Body: Excerpts with short analyses:

"A new study suggests that when men were exposed to a different actress while watching porn, they ejaculated quicker and produced more semen."

What? You mean men are more excited about a new girl than one they've already experienced?! That can't be! /s

There has been very little research on how semen ejaculation is allocated in different situations in humans.

Well yeah, science is already proving too many differences between the "equal" sexes. We certainly mustn't encourage such behavior! /s

For the most part, humans seem to lack many of these adaptations we see in other animals, which makes sense because humans are predominantly monogamous.

Unsubstantiated statement submitted as fact and not sourced because it's "common knowledge". Truth is, Alpha males very rarely remained monogamous throughout history. Beta's had no choice, but they obviously would prefer not to and every "pig" husband on tv proves it.

When the participants watched the seventh film with the new actress, the total number of motile sperm, the speed and amount of ejaculation increased.

Prior to this they state that men didn't decrease in sperm production with a higher number of experiences with the same "actress". Makes sense, we don't wanna hurt our chances of offspring. However, as soon as there's a new girl we start performing on a whole new (higher) level. Not at all surprising. --(Note: reminds me of a post from some SJW in RPW trying to make them believe they should avoid "high partner count men". Lol, happily she failed miserably.)

This research adds to a rapidly growing body of work indicating that human sexual psychology and physiology includes adaptation to prevent or to more effectively participate in sperm competition.

At the end a psychologist confirms what we already know, mating is a competition and we have adopted traits to win that fight.

Lessons Learned

  1. Men were made to mate with as many women as possible.
  2. The newer the girl the more excited we are.
  3. "Love" is a competition and you need to play to win.
  4. This is just my hypothesis, but it's supported by this so:
    "Jealousy evolved as a way to motivate men to protect their mate long enough to ensure their offspring would thrive." I expect in the very beginning we just fucked (raped) everything and a very small percentage of those offspring ever actually became an adult. Only way to increase population size was to protect the women from being raped/killed by something else in the very dangerous world that they were laughably incapable of surviving.

Jealousy - "Well if I gotta protect her and kill more shit to feed her and the kid I'm sure as shit not gonna let Frank fuck her".

Full article Here

Study Here.

As an aside, for guys in an LTR, or intending to enter into one:

If you lead a worthy mate on a strong path of self improvement she can be made new quite often. How do you know if she's "worthy"? If she can keep up :)