The invasion began where the land met the sea and spread throughout the continents forever changing them. The warring sides fought with every ounce of strength. Survival was the prize.

Those that had occupied the land from time immemorial held fast so long as the interlopers were contained on the beaches cut off from the fertile fields further inland. The sand and scree that lined the water's edge offered little that the invaders could rely on for a firm grip. However, they had an advantage. They were more modern, better evolved than their predecessors, and their victory was a foregone conclusion. Looking back from a more civilized age, some could argue that their advantage was unfair. Others would argue that it was simply a reality.

It little mattered for, in time, the vanquished vanished and the victors thrived until a new invader arrived on those shores and the story was repeated. However, there was a difference. This interloper had different needs than the established population which ceded territory begrudgingly but thrived on what remained uncontested by the new comers. Thus the new and old subsisted side-by-side. 

In time they interbred where they co-mingled by the borders and new populations arose. Each one caused some initial disruption until the division of territory could be fought over and resolved.

An age or two passed and then a new invasion arrived on that shore. It began in the east and then clawed and crawled its way inland until it spanned the continent. This new threat found havens in all different types of terrain. Wetlands, plains, foothills, mountains, and desserts seemed equally inviting to its habitation. 

The new invaders practiced apartheid. There would be no intermingling or interbreeding between the old and the new. 

Scholars have never questioned the ethics of any one of these invasions. They are accepted as fact without any moral judgment despite the fact that each won the land through conquest. How could anyone judge one conquest more valid than any other?

Where did these invasions occur and who were the invaders? Where is everywhere on planet earth and, most likely, on every other planet on which life occurs. Who is more complex. The first invaders were the plants. The ones that followed were the animals. Both came in waves of gradually evolving species.

Ultimately, conquest became the business of man who has claimed every square inch of the planet by conquest. Successive generations have taken the planet by conquest generation by generation. Those who lie at the feet of conquerors complain that the land was stolen from them, but what makes their conquest more legitimate than those that followed? One wonders...