You might say Robert Jordan is the keeper of the flame by preserving the family's sourdough starter for so many years.
As Jordan explains in the video, his mother, Jean Rentz Jordan, who passed away in 2013 at the age of 88, had eaten pancakes as a child from this same sourdough starter. Though he is not able to verify the claim, it was family lore that the starter came from his grandmother during the Alaska Gold Rush of 1898.
This sourdough starter consists of flour and whole milk. The sour flavor is a result of the yeast and a certain type of bacteria (Lactobacillus) present in the air (or in the flour itself) that remain in balance with each other. Too great a population of yeast, and the bacteria are not able to reproduce, without which, there can be no sourdough style dough.
For those who want to begin their own starter from scratch, here are several recipes:
Sunset's Reliable Sourdough Starter (Sunset Magazine)
Basic Sourdough Starter (The San Francisco Exploratorium)
How to Make Your Own Sourdough Starter (the Kitchn)
Basic instructions for maintaining the sourdough starter, and creating the batter to make fresh pancake mix (as seen in the video) can be found on Cooking Up a Story.