Over the years, people have debated about the validity of so-called "feral children". Though dozens of incidents have made the news, most of them have turned out to be misunderstandings of medical conditions or fraudulent acts in which adults have manipulated children with developmental disorders into acting as if they were raised by animals.
But there have been some genuine cases in the past.
One of the most recent - and most convincing - stories comes from Marcos Rodriguez Pantoja, a "real-life Mowgli" who claims that he was raised by wolves.
According to him, he was around six or seven-years-old when his father sold him to work in the Sierra Morena mountains. He was assigned to help out an old man who worked as a goatherd, but the job didn't last long. Within months, the elderly man passed away, leaving Pantoja all alone in the wild.
Pantoja - now 72-years-old - says that he could have returned home, but his family had been abusive, and so he decided it was better to stay on his own. However, he couldn't have survived without the help of the animals that lived in the area.
"The animals guided me as to what to eat. Whatever they ate, I ate," he said in an interview with BBC. "The wild boars ate tubers buried under the soil. They found them because they smelled them. When they were digging the soil looking for them, I threw a stone at them - they would run away and then I would steal the tubers."
He recalls one incident in which he played with some wolf cubs, and got accepted by the pack.
"After feeding her pups, [a mother wolf] threw me a piece of meat. I didn't want to touch it because I thought she was going to attack me, but she was pushing the meat with her nose. I took it, ate it, and thought she was going to bite me, but she put her tongue out, and started to lick me. After that, I was one of the family."
He lived like that for more than a decade until he was discovered by the Civil Guard at the age of 19. He was taken away from his animal family and forced to reintegrate with society, but he didn't adjust very well.
"I could not cope with so much noise… the cars… and people going back and forwards like ants. But at least ants all go in the same direction! People went everywhere! I was scared of crossing the road!" he said.
He was cheated and abused by employers, exploited by people who saw him as a naive and easy target, and generally rejected by those who considered him to be abnormal. At times, the human world became so unbearable that he tried to return to the mountains, but he says that "it is not what it used to be."
"You can tell that [the wolves] are right there, you hear them panting, it gives you goosebumps … but it’s not that easy to see them," he said. "There are wolves and if I call out to them they are going to respond, but they are not going to approach me. I smell like people, I wear cologne."
In the present day, Pantoja lives in a small village, and says his community accepts him. He frequently gives talks about his past experiences and his love for animals and the environment, and is supported in this by a charity called "Amig@s das Arbores".
Life may be harder for him now, but at least he has a place to stay and an outlet to share his adventures with people who care.