Rock Human

The Rock Humans (岩人間) are a race of mysterious beings that serve as antagonists in Part VIII: JoJolion.

Summary
The Rock Humans are a race of idiosyncratic humans whose original forms take on a "rock-like" composition. In this form, most biological activities come to a halt and they're able to endure high and low temperatures, dryness and other things in nature.

While they are generally represented as humans, Iwasuke, a dog of unknown origin, also appears to have similar abilities and is described as a rock dog.

Hibernation
Sleep hits suddenly at different times depending on the individual and will last anywhere from 30 to 90 days but after waking up, a Rock Human won't sleep again for at least two months. While hibernating, breathing is halted, though a small amount of skin respiration is required through the cracks found on their outer layer. If necessary, they can stay in hibernation for 25 years and sustain temperatures as high as 950°C and as low as -240°C. Their body heat, as well as scent, disappear while dormant causing various fungi, moss and even pearls to grow on their body.

The means by which they harden into stone involve an intricate cell system that stores moisture within the interior of each cell and is protected by carbon-rich cell walls. Any item a Rock Human carries when he's hibernating will be covered with a hard membrane which tears off like a scab upon awakening.

When hibernating, Rock Humans will prefer places such as shrine grounds, parks with statues, gardens of expensive houses, and underneath maple trees with squirrels in them. They will generally avoid sleeping in areas that were previously flooded, or have high chances of being rained on by tree sap or bird poop.

Biology
There are both male and female Rock Humans who procreate and give birth much like humans. Visually, there are no differences between them and humans, though their skin upon awakening appears slightly moist, damp and erotic.

Rock Humans do not grow gradually, but "molt" their whole bodies at once every 6 years. This transformation occurs during their sleep, and for some unknown reason, the pose they make when asleep will change each time. It is believed that Rock Humans can live for 240 years. When a Rock Human dies, it leaves no corpse, as it crumbles away into rocks.

Behavior
Rock Humans eat plants, fruits, nuts, meat, fish, and all other forms of life. They enjoy honey, and all are allergic to mangoes.

They hold a certain reverence for the power found within the Earth and nature. Because they are fundamentally able to live through weather changes, they require no assets such as a house or land.

However, they are unable to safely coexist or mutually understand human society. Because their natural environment is slowly being taken over by human development, some have taken the form of "parasites" by falsely entering the family registry system to maintain property and assets. However, due to their extensive hibernation, Rock Humans cannot go to school or hold regular jobs, instead working in occupations that allow irregular business hours. Rock Humans also rarely fall in love with normal humans, but if they do, there's a 97.5% chance it will end in disaster. The breakups between humans and Rock Humans are said to end in the form of murder

Abilities and Powers
Rock Skin: Presumably separate from hibernation, each Rock Man has the ability to shift their outer appearance from a normal human into a rock-like state and vice versa at will. In their rock form, they are able to camouflage into their surroundings, and improve durability to some extent. The ability to stay human requires some type of focus however, as Aishou describes his rock form as something he was born with, but unable to control at a younger age. Yotsuyu, who is presumably more experienced in controlling it, is able to revert to human, rock, and a hybrid where he can still move despite having a rock-like appearance.

Stand: 95% of Rock Human possess Stands, such a high number of Stand users within their population isn't explained.

Trivia

 * The concept of the Rock Humans is similar to the Pillar Men in Battle Tendency.
 * It also may be in slight reference to minor Diamond is Unbreakable antagonist Anjuro Katagiri, who literally becomes a "rock human" (a human fused with a rock) after his encounter with Josuke.
 * In Japanese mythology, the legend of the tale of flower goddess Konohahasakyua no Hime tells that she and her sister, the earthen goddess Iwanaga Hime, were the daughters of the mountain god Oyamatsumi. Upon having met the agricultural and vegetation god Ningi no Kami and fallen in love with him at the seashore, Oyamatsumi desired him to marry Iwanaga Hime, but reluctantly gave into Konohahasakyua's and Ningi no Kami's romance. Upon their marriage, their influence was said to have been responsible, instead of being as enduring as stones, for humans to be as fleeting yet as beautiful as flowers. The Rock Humans may likely be the insight to the humans birthed by the possible marriage of Iwanaga Hime and Ningi no Kami.
 * Although their motives are unclear, at this point in the manga the "Rock Humans" are the collective antagonists of JoJolion.