The general concept behind this behemoth is how we evolved from monkeys into what we are today. The ancient monkeys are living in the trees and then symbolically pass through the window in the trees to reach the plains of Africa and slowly evolve into humans as the climate and world changes. Over time, they eventually learn to create fire, cook, make tools and eventually create ancient and modern structures. It's a fascinating topic to me and one that will keep me focused for the duration. Here is the basic flow of the painting (see pictures).
From bottom to top:
10,000,000BC: Apes/Monkey's living in trees in Africa.
5,000,000BC: Africa is drying up, so in order to survive, we leave the trees and start walking.
1,000,000BC: Africa is now a grassland and we have learned to use fire and tools.
500,000BC: We migrate to other continents and subsequently, evolve into different types of human beings.
100,000BC: Modern Humans Beings emerge.
10,000BC: Human Beings begin to settle down and start to create civilizations.
1,000BC: Huge monuments and structures are built, empires emerge.
100BC-100AD: Ancient Civilizations are at their artistic prime.
500AD: Structures are now being built all over the world.
1,000AD: Medieval times in Europe, North America is flourishing.
1,500AD: Renaissance period, Pre-Columbian cultures are at their peak.
1,800AD/Present Day: Industrial revolution, technology.