The number of sports that continue to thrive today is exceedingly small compared to the number of sports that have ever been played. There are 34 sports in the Summer Olympics and fifteen sports in the Winter Olympics.This is essentially the sum total of all significant sports that are still alive and growing today, save for American football, cricket, lacrosse, auto racing, and squash, which are too regionally specific to be included in the Olympics.

The number of sports that have ever existed is uncountable. Caricatures of sprinting and wrestling date back to 13000 BCE, and ever since humans have had free time, they have created games to play.

It would have been easy to predict the perpetuation of some sports, like running, swimming, and fencing, because these are things that are useful to human survival, and being able to run fast or fight well with a sword has obvious value. But for some sports—generally the sports we consider to be games, like basketball—this value is much less obvious. Why does being able to shoot a ball through a hoop better than anybody else earn you millions of dollars a year, while swimming faster than anybody else only earns you fame among swimmers and a brief moment of worldwide recognition every four years?

“Game” is not a clear-cut word; a game can be a sport, like basketball, or not a sport, like chess. All games consist of two forces acting against each other that have a direct effect on each other. Games almost always involve at least one human, and all sports that are games involve at least two. In games that involve only one human, the force acting against that human can be a luck-based challenge, as in solitaire. It can also be a challenge designed by another human, as in single-player video games, American Ninja Warrior (ANW), or (unintentionally) parkour. Of these, we consider solitaire and video games to be “games” and ANW and parkour to be only “sports” because the first two don’t involve physical activity.

There are no racing sports that we can consider games. Running, swimming, rowing, cycling, sledding, and skiing are not games because games require arbitrary scoring systems.

Most games today have adopted a scoring system in which one success equals one point, and getting more points than the other team(s). This is done for simplicity: all the games we love today are simple in essence.

Some sports and games defy these norms; in football, six points are awarded for a touchdown and three are awarded for a field goal, which gives a team multiple options to score and makes the game more interesting.

Sports that are scored subjectively are almost always not games. These include figure skating, gymnastics, and dance. However, these sports are ruled out as games by the earlier definition that games must involve direct competition; the competition is indirect like a racing sport, but instead of competing alongside each other, each person or team competes one at a time.

Hand-to-hand combat sports, like wrestling, boxing, and martial arts, though they involve direct competition and an arbitrary scoring system, are certainly not games.

It’s difficult to say why these are not games. One possible explanation is that they don’t use instruments besides the human body like balls or bats, so they don’t have specific implements that can be improved upon and make them different from everyday life.

Fencing is another sport that involves combat, but its use of swords causes it to blur the line between sport and sport-game, and because of this it is perhaps one of the most difficult sports to classify.

Sem Hoogendoorn, nationally-ranked fencer and MHS senior, considers fencing both a sport and a game.

“Everyone has a different style of creating, manipulating, and masking the patterns of the game. No bout is ever the same, and it’s fun to apply different skills and techniques to win,” he said.

Hoogendoorn’s idea of what games are all about can help us discern the reason that some games die, some survive, and some prosper.

The most important factor in making a game interesting is the ability for players to do unexpected things within the context, rules, and mechanics laid out by the game. Players have innovated in basketball forever, beginning with the dribble, which was not in the original rules of the game, and extending to the pick-and-roll and as far as Lakers coach Phil Jackson’s unstoppable triangle offense.

However, for the game to be balanced, these unexpected innovations must have counterplay. The game must stand up to the cheesiest strategies that can be imagined by teams without falling apart, and it must still be interesting to watch.

For example, over the last few years, basketball has centralized around the three-point shot due to the shooting prowess of players like Steph Curry, who is able to hit more than 43% of his shots from behind the three-point arc, and his similarly well-shooting team, the Golden State Warriors. Even now, though, the game is beginning to shift again with the advent of skilled, athletic bigmen like Giannis Antetokounmpo and Joel Embiid, and it will surely continue to shift from there.

By the definitions we’ve laid out, only sixteen of the 49 sports in the Olympics are games. These are badminton, baseball, basketball, beach volleyball, indoor volleyball, fencing, field hockey, golf, handball, rugby, soccer, tennis, table tennis, water polo, curling, and hockey. Adding the four that are not in the Olympics (football, cricket, lacrosse, and squash) gives us twenty world-recognized and surviving sport-games out of the unimaginably large pool of games that have ever existed.

Some of these games only have cult followings and are likely to always be overshadowed by more popular games. The most popular games in the world are unquestionably soccer and basketball, followed closely by the regional games of football, baseball, cricket, and tennis. Golf, hockey, and rugby are third-tier worldwide sport-games that have large followings, and the rest of these sports are followed only by a small, specialized group of people. Therefore, we can only consider about nine sport-games to be popular today.

These sports are popular because of their depth and variability, and because their concepts are simple to grasp but require great skill. That’s why it’s fun to watch the masters of the sports that we watch in the most volume. But the fact that these sports have been designed perfectly to be the games they are—the distance from home plate to first base has not changed in at least 130 years, for example—is mostly due to natural selection and random chance. Once a sport is fun, it relies on its players and officials to make it balanced. In a way, we all had hands in making the games we love today.