It was, without question, the end of Homo sapiens' dominion of the Earth.
In the final few decades of his mastery mankind began to sputter and die like a poorly maintained machine. The precious resources extracted from the Earth had been drained into oblivion. Diseases, made nigh-invincible by a century of combat with vaccines, killed millions and affected millions more. Land which had supplied the exponentially growing human species with suitable farmland slowly turned to nutrient-barren wastelands. The rapidly increasing global climate wreaked havoc on the poles and, in turn, flooded the coasts and evicted any people living there. War erupted across the world as governments struggled to remain in control of the restless civilian population. Worst of all, overhunting, destruction of habitats, urbanization, and pollution poisoned the already impoverished biosphere. As the human race collapsed from attacks on all sides a miraculous event, unprecedented anywhere in history, gave hope to those who survived to see it.
It was, without question, the single most important event since the rainforests that housed our distant ancestors gave way to savanna and set the development of mankind in motion.
A rift in time leading to an unknown location would be our salvation. What little organized government and science that remained worked together to gather people and technology to support a dozen functional colonies. These colonies, inhabited by no more than 300 people each, would be the Adam and Eve of a new generation of humankind in the world beyond the rift.
This time we would do better. Our population would remain low, our impact minimal, our accumulated scientific knowledge allowing us to survive without excess of people or pollution. We could learn to live with the environment rather than destroying and warping it to suit our needs. Our technological advancements, especially those in agriculture, could be perfected to leave the planet almost as we found it. Man, so set in his ways that he nearly drove himself into extinction, would alter his behaviour if he wished to succeed in the land awaiting him.
This time things would be different.