An amazing fan theory asserts that Arnold Schwarzenegger’s Predator character Major ‘Dutch’ Schaefer was used as the template for his Terminator model 101. Consequently, that would make Predator a prequel to the Terminator films.
In the 1987 movie Predator, the US military send a crack team of ex-army guerrilla specialists, led by Dutch, into a South American jungle to “obtain some intel.” However, what they find in the jungle is the ultimate hunter; an alien who can turn invisible, see using heat vision and move by jumping from tree to tree. One of the local female villagers describes the alien as “El Diablo cazadores de hombres … the demon that makes trophies of man.” It turns out that the military knew there was an alien in jungle, and Apollo Creed (sorry, we mean Dillon) lied to Dutch in order to get his team to kill the Predator.
Things don’t all go to plan though as the Predator hunts Dutch’s team and kills them one by one, including Dillon, until only Dutch himself is left. Schwarzenegger eventually killed the alien by covering himself in mud to block the Predator’s heat vision and then luring him into an old-school trap that he built in the jungle. At the end of the movie, Dutch is picked up by a military helicopter and we never hear what happens to him next.

We should note that the novelisations of the Predator movies claim that Dutch was suffering from radiation poisoning. But, the novelisations are not regarded as canon.
Alternatively, we can turn to Capcom’s 1994 Alien vs. Predator arcade game for answers. This game is considered as canon because, amongst other things, it propagates the idea that Predators and Aliens belong together. In the arcade game, you are introduced to a cyborg called Major Dutch Schaefer and it’s clear that the cyborg was designed based on Schwarzenegger’s face and body. Why would the cyborg resemble Schwarzenegger’s character? Well, the theory is that the US military knew about the alien super hunters and wanted to build a cyborg to fight them, and in Dutch they found the perfect template for their prototype cyborg. This means that the military purposely sent Schwarzenegger’s team into the jungle to see if any of them were worthy of being this robotic template (intertwining perfectly with the events of the first Predator film).

Image credit: Capcom
This theory is backed up when you learn about the US government’s Other World Lifeforms Taskforce in the second Predator movie. It turns out that the government were investigating the Predators for years before Dutch’s team went into the jungle. They must have known that the alien likes to challenge himself and fight against the best warriors that Earth has to offer. This would explain why Dutch vanished after the events of the first film and re-appeared as a cyborg in the arcade game, it was all planned.
But how does this link to the Terminator franchise? The answer: Cyberdyne Systems. The cyborg version of Major Dutch Schaefer was built by Cyberdyne Systems. In Schaefer’s profile in the Alien vs. Predator arcade game, his serial number is CDS-170A3. Of course, the CDS stands for Cyberdyne Systems. A side note, rumour has it that the original script for the first Alien vs. Predator movie closely mirrored the arcade game with a cyborg Dutch fighting Aliens and Predators; this didn’t go through for a number of reasons including, for instance, Schwarzenegger being in political office at the time of the film’s production.
Moreover, if we consider the film Terminator 3: Rise of The Machines, we see that the US government was working quite closely with Cyberdyne Systems to develop the Terminator machines. It’s also clear that the military were searching for the perfect soldier to use as their template for the prototype of the Terminator model 101. For example, in the Terminator 2 novels and in deleted scenes from the Terminator 3 movie, they show 2 different soldiers (Dieter von Rossbach and Sgt. William Candy) being chosen as the template for the Terminator. The choice of either of these 2 soldiers are not considered canon, however, because the Terminator movies ignored Dieter von Rossbach from the Terminator 2 novelisation, and the choice of William Candy in Terminator 3 was relegated to the deleted scenes as a mere easter egg. If the Terminator, Predator and Alien franchises all exist in the same universe then there could only be one possible choice, only one soldier deemed worthy enough of being the Terminator prototype; Major Dutch Schaefer.
Another point we must consider is the fact that the 1st and 2nd Terminator movies, as well as the 2nd Alien movie, were all directed by the same genius, James Cameron. In his Terminator movies, Cyberdyne Systems create the cyborgs and in his Alien movie he also has cyborgs, this time created by Hyperdyne Systems. For Cameron’s movie universe it seems obvious that Cyberdyne Systems evolves into Hyperdyne Systems. Cyborg technology evolved from Cyber Dutch to the Terminator and then on to advanced Synthetics such as Ash and Bishop. More importantly, the cyborg Ash, from the 1st Alien movie (not even directed by Cameron), had the serial number Hyperdyne Systems 120-A/2. Reformatting makes it HDS-120A2, strikingly similar to cyborg Dutch’s serial number CDS-170A3.
And there you have it, the Terminator model 101 is Major Dutch Schaefer from Predator!!