Dr. Stone: What Is Medusa? & Why Did They Petrify Humanity?

Petrification Device

When it comes to the world of Dr. Stone, there is no doubt that the lingering mystery that Senku and his friends sought to solve was related to the global petrification of humankind. That was when Senku learned during the events of the Treasure Island arc that there was a group of people that used devices that were called Medusas. So, what is the Medusa in Dr. Stone?

The Medusas are the petrification devices responsible for turning humanity into stone more than 3,700 years before the events of Dr. Stone. These devices are sentient beings that are stationed on the moon and were looking to help the advancement of intelligent life forms by giving them “eternal life.”

There is no doubt that the biggest mystery surrounding the Medusas is the nature of these entities and why they exist. These were all answered in the events of the Moon Mission arc when Senku and his allies learned more about the petrification devices and what they were after. So, with that said, let’s look at what the Medusas are and why they petrified humanity.

The Medusa Petrification Devices Explained

The entire storyline of Dr. Stone explores Senku Ishigami’s quest to bring human civilization back on its feet after the entire human race was turned into stone 3,700 years ago. Of course, Senku returned from his petrification almost by pure luck and found allies that helped him establish the Kingdom of Science, which pursued the advancement of humanity and Senku’s mission to bring the world back to where it was before the entire petrification event.

petrified world

While Senku’s current goal is to try to bring human civilization back on its feet, the Treasure Island arc in the storyline allowed us to learn more about what was responsible for turning people into stone. The only thing we know about the entire petrification event 3,700 years ago was that a green light enveloped the entire planet and turned people into stone. But Byakuya Ishigami (Senku’s adoptive father) and a few other International Space Station astronauts were spared from the petrification event. As such, they could return to the planet and establish a small community of humans that Senku eventually befriended 3,700 years later.

As such, it is clear that the entire petrification event only affected the people on the planet. And during the Treasure Island arc, Senku learned that a group of people had weapons capable of turning people into stone.


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These weapons were called Medusa by Senku, as this was a nod to the Greek mythology gorgon that could turn people into stone with just a stare. The weapons were not invented by humankind but had actually fallen to earth from the sky years ago. And the very same petrification devices, as Senku observed, could heal humans whenever they were returned from their petrified states.

It was also during the same arc that Senku and the others were able to intercept a signal that seemingly came from the devices. These signals constantly repeated the word “why,” and that was why Senku and his allies called the mysterious entity “Why-Man.” They learned from the signals that Why-Man was attempting to turn humanity into stone once more, and that meant that Senku needed to do something about Why-Man before it could undo the scientific progress that he and his allies worked so hard on.

petfificatio devices falling

The subsequent arcs that followed the discovery of Why-Man allowed Senku and the others to form allies worldwide to share scientific knowledge and resources to pursue the one thing humanity often calls its greatest accomplishment—sending a person to the moon. That’s because the Why-Man signals come from a dark spot on the moon itself.

During the Moon Mission arc, Senku and the others discovered that Why-Man was not a single person but was actually a collection of sentient petrification devices that were still “alive.” The dark spot on the moon was actually a mass of Medusa devices that could think, unlike the “dead” petrification weapons that were used during the events of the Treasure Island arc.

In that regard, the Medusas are sentient machine-like life forms capable of independent thought. That means they are alien regarding their origin and were not created by humanity. These petrification devices were the ones that initiated the planet-wide petrification that happened more than 3,700 years ago. And the fact that they initiated this planet-wide petrification from the moon was why Byakuya and the other astronauts were spared from this phenomenon.

Why Did the Medusas Petrify Humanity?

Senku and his allies learned more about the petrification devices and their goals during the Moon Mission arc. They learned they needed someone to replace the diamond batteries that powered them, as they couldn’t do this themselves. In exchange, they offered “eternal life” by turning intelligent life forms into stone.

Why man

We know that those whose petrification devices turn into stone live forever in their petrified states. When they are de-petrified, all of their wounds and illnesses are healed. That is why the Medusas are basically able to offer eternal life to intelligent life forms. In exchange, their batteries needed to be replaced. In Dr. Xeno’s words, they are “parasites,” although Senku didn’t share the same observation.

So, the reason why the Medusas petrified humanity was that they wanted to offer humankind the ability to live longer and become a more advanced civilization by being able to live lives that are basically eternal. But this wasn’t something that humanity agreed to when the Medusas petrified all humankind. As such, humanity was left in the dark when the petrification devices decided to petrify humankind and push human civilization back to the Stone Age.


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But Senku was able to talk some sense into the petrification devices to convince them that humanity was not what they thought it was. As such, they all agreed to leave humankind alone to search the cosmos for other intelligent life forms they could work with. 

Nevertheless, one Medusa stayed behind and returned with Senku and the others to Earth so that it could learn more about humanity and allow the Kingdom of Science to study it. Senku observed that this Medusa device was unlike the others because it was much more curious.

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