A clone is a being that has been created/born through the DNA of the person that they were cloned from. This person is called the clone template. While clones are not created by nature, they are still living beings that possess self awareness, consciousness, and independent thought. The genetics of clones could be manipulated, with the creators of the clones writing and programming specific instructions into the clone's genes. These could result in physical enhancements, such as enhanced physical strength, mobility, and resilience. It could also result in accelerated aging at the biological age of their template when they were cloned.
In 1972, Zero, the leader of the Patriots, began to fear that the organization's icon Big Boss would leave due to their different views of the The Boss's will. To this end, he decided to clone the legendary soldier to both replace Big Boss as the Patriots' icon and to be used as weapons against him. The concept of cloning Big Boss was acknowledged as early as Operation Snake Eater, where Para-Medic informed Big Boss, then known as Naked Snake, about the possibilities of it.
After Big Boss sustained an injury in battle,[note 1] Zero had Dr. Clark take Big Boss' DNA and use it in a project to create clones of him. This project became known as Les Enfants Terribles. After dozens of failures, Dr. Clark finally managed to create two clones using her assistant's egg cells and EVA as the surrogate mother.
The two clones, also known as the Twin Snakes, were called Solid Snake, who had the recessive genes, while the other was called Liquid Snake, who got the dominant genes. A third clone was created later on, who had both types of genes. This clone was called Solidus Snake.
As Big Boss was 37 years old when he was cloned, the clones would start to suffer accelerated aging when they reach their late thirties, though Solidus suffered this very early in his life. This was a fail safe in case the clones were either stolen by the enemy or turned against Zero.
Although they were cloned from their father, the Twin Snakes all had different DNA, though it took stronger technology to detect this.
Although not clones in a strict sense, the Next-Generation Special Forces were created through a similar manner, which Liquid Snake referred to as "receiving [the NGSF's] soldier genes digitally."
Accelerated aging and sterility
Each known clone had accelerated aging (or Werner Syndrome) written into their genes in order to provide a fail-safe against the clones' genetic information falling into enemy hands, or if the clones turned against the Patriots under their own volition. This aging started when the clones reached the age of their template when they were cloned. Despite being preceded by his brothers, Solidus appeared more aged than the other two clones in his later life. Physical aging did not weaken physical abilities, allowing a clone to having the strength, speed, and resilience of a human in their prime.
All three clones also lacked the ability to reproduce, which according to Solidus, had been "conveniently" written into the clones' DNA. It is this that drove Solidus to leave behind a lasting legacy to the world, due to his forthcoming death from advanced aging. All three clones also had terminator genes so that they could not be cloned.
Due to the nature of their conception and development, the Les Enfants Terribles children possessed enhanced natural abilities and resilience, surviving and withstanding physical and mental situations that would result in an average human's death or mental breaking. Even in his early childhood, Eli was superhumanly strong, fast, and resilient, with him able to fight resist the effects of tranquilizers, being brutally attacked by Venom Snake, and even being able to fight a men much larger and more skilled than he was. Snake showed nearly inhuman agility and was able to jump 7 feet or more and perform several aerial flips while dodging machine gun fire, all with great ease, while he was in his prime and equipped with his Sneaking Suit. Also, physical strength and resilience were still as high as a human in their prime when the accelerated aging was in affect. In addition, Ocelot implied that the Les Enfant Terribles project also resulted in the children having a heightened and natural aptitude with piloting vehicles.[7
Behind the scenes
Cloning is a concept within the Metal Gear series, introduced into the series with Metal Gear Solid via the Les Enfants Terribles project. Because of the main character Solid Snake being revealed to be a byproduct of the Les Enfants Terribles project, and to some extent, the central character Big Boss's ties to the project in question, cloning also plays an important role in the franchise. The concept of Solid Snake being a clone was created by Hideo Kojima as a stop-gap measure to both ensure that the enemy group Solid Snake was to face against, in particular their leader, was a credible threat to him, and at the same time maintain continuity with his being a seasoned veteran. He would later admit that he considered it "cheating" around the time of Metal Gear Solid 3: Snake Eater.
Aside from the Les Enfants Terribles clones in the main series, the Metal Gear Acid subseries had cloning involved with the creation of the character Snake, who was a clone of Solid Snake from the same series.