Due to the quite recent popularity of Japanese comic books (known more conventionally as manga these days), there are people who may understand manga as a contemporary invention, though more truthfully, it has been around for several years.
The tradition of story-telling has existed as a cultural and social interaction between humans for several thousand years. Art is another form of pastime that has existed amongst story-telling traditions.
In Japan, many folk tales and traditional stories had a combination of both these elements; written text and pictures to accompany. At the time, they had been written and drawn on scrolls made out of materials that had actually not been paper due to its price. Also, because the idea of a book had not come into existence until several years later, the folk tales and stories were typically quite long in length. Literally.
A majority of the stories written and drawn on these scrolls were related to war, or religious ideas and concepts taken from Buddhism. Due to the Silk Road relations, there are many similarities between folk tales that exist in China and Japan, and also traces from India.
An advantage of having these stories all documented in physical form was that it had allowed editing to be done. Editing could allow people to cut sections of the scroll and have them replaced to allow better flow for stories. Though, this could be a disadvantage as well; one cannot be too positive that some scrolls had not been manipulated or tampered with at some point in time.
An interesting thing to note about the pictures on these scrolls is their use of time and space, and the general scale of the entire image. It is normal to have the same individual be in various places at once in the exact same picture on the scroll. A pattern existed with the scrolls where there would be a section of text, image next, text again and so on. The pictures were fairly large, so they had portrayed many components of the story at one time, whereas in comparison for example, the picture books we are used to seeing, they tend to focus on one element of the story and have an image to specifically draw our attention to that one single detail. This could have had in influence on today’s current manga, and explain the repetitiveness of images and panels.
Scrolls eventually gained popularity in medieval Japan and adapted a shape closer to today’s book. The styles, stories and ideas have all evolved over time to become what we know as today’s manga.