In 1917 people lived on the side of the mountains.
One tribe built floating hut villages by the river for shelter. Every day, they went around the jungle to get food and supplies that they could put to use at home.
During that time, there was a war on the other side of the planet. Some aircraft and spaceship debris fell from the sky. They started to collect the parts they found and brought them home to their tribe. They came up with the idea that one day, after putting these parts together, they would create something that will change everything. At one time, they thought they could assemble a machine that will make their lives better.
Finally, on a fine day, one of them woke up early in the morning and went straight to the machine. He tried his best to fix it and wanted to see if it worked. He felt that they have worked on it long enough and decided to at long last turn it on. At that moment, he discovered that it was not a warship but a time machine. He ran it and made it work.
He eagerly called out every member of his tribe to join him for the time of change.