Warning: contains spoilers for Dr. STONE!After 228 chapters, Dr. STONE finally reveals the mystery behind the petrification of Planet Earth that kickstarted the science adventure drama featured in the pages of Shonen Jump. The identity of the villainous Why-man and their connection with the petrifying devices called Medusas is finally unveiled.

Dr. STONE - written by Riichiro Inagaki with art by Boichi - begins with Earth struck by the greatest calamity in history. A "petrifying beam" traverses the length of the planet, encasing all living beings in stone and turning them into statues. The mysterious energy, however, also preserves people from aging or dying, so 3700 years after the event, scientific prodigy Senku Ishigami, the son of Japanese astronaut Byakuya, wakes up due to an accident and gets started on his mission to rebuild human civilization starting from the Stone Age, picking up friends and enemies along the way. Senku's group even discovers the source of the petrification beam, an advanced technological device they dub "Medusa." Previously, it has been revealed that Medusa is activated through a vocal command, proving that the petrifying beam was not an accident, but the work of an unknown enemy of humanity.

The Medusa Devices Petrified Humanity Themselves

The "Kingdom of Science" founded by Senku and his friends first learns of the existence of this being when they activate a powerful radio tower, picking up a Morse code signal repeating the same word: "Why?" They dub the source "Why-man" and confirm they are in fact an enemy when they try to use the group's radio devices to activate a Medusa, in order to petrify humanity once again. The Kingdom of Science finally learns that the source of Why-man's signal is on the Moon, putting them in front of their biggest challenge yet: building a vehicle for space travel with the limited technology they possess.

The threat of Why-man is just too big to be ignored, as all their labors to rebuild civilization will be rendered pointless if the Why-man manages to activate a petrification beam again. Many years pass, in which Senku forges an alliance with a former enemy who is the only one on his level of intelligence, American scientist Dr. Xeno, and resources are gathered by traveling the world and building entire cities with the sole purpose of producing the materials needed for space travel. Finally, a team composed of Senku, Kohaku, and Stanley arrives on the Moon, and the truth they discover there is staggering.

On the Moon's surface there is a "black spot," first located by Kohaku using a satellite built by the Kingdom of Science. Arriving there, the group finds out that the spot is made by a huge mass of writhing, swirling Medusa devices. Humanity's enemy, Why-man, is none other than the Medusas themselves. Senku describes them as machine lifeforms, while Xeno calls them "mechanical parasites." Apparently, the Medusas' purpose is to have someone perform maintenance on them, such as replacing the diamond batteries that power them. The petrification effect actually offers humans eternal life, as it not only preserves them from aging but can also be used to heal fatal wounds (as Senku and the others discovered early on.) By offering everlasting life, the Medusas are spurring intelligent life to better itself, and to march toward progress. This is a hypothesis posed by Senku and Xeno, but the Medusas actually confirm it on the spot.

How Did Dr. STONE End?

Dr. STONE's final chapter (#232) was released on March 7, 2022. Senku was able to communicate with the Medusa devices, still going by "Why-man." He managed to convince the machine lifeforms that petrifying humanity would never actually get them what they truly wanted: maintenance and the construction of more Medusa units. Senku did offer to help them if they ceased petrification, but the mechanical parasites ultimately decided that humans weren't smart enough to do what they needed, and left the Solar System in search of life elsewhere. However, one unit stayed behind, offering to allow itself to be studied to see what humanity was really capable of.

With the threat gone, Senku turned his attention towards his craziest invention yet. Determined to save the many people who were turned to stone and destroyed, or otherwise unable to return, Senku uses the knowledge gained from the Why-man unit to begin constructing a time machine. The story ends with the hope that they'll be able to go back in time and stop the original petrification event, even if it may take decades or centuries to accomplish. Whether the answer of machine aliens being behind Dr. STONE's petrification event is a satisfying one is a question best left to each fan individually, but the series certainly ended with as much enthusiasm for science as it started with.