You and your friends are in highschool, and have just perfected a time machine. You all intend to use it to travel to the Cretaceous era, around 140 million years ago, to witness the dinosaurs. Upon entering that time, you all see the dinosaurs, and something else. Modern humans, Homo sapiens, along with neanderthals, Denisovans, Homo floresiensis, Homo rhodesiensis, homo Heidelbergensis and Homo luzonensis, living together in what appears to be civilization far more advanced than the present day. They have domesticated the Cretaceous dinosaurs, mastered space travel, nuclear and renewable energy, cities and civilizations far larger than what's possible today, and energy weapons, both handheld and mounted. You check the time machine again. There's no sign of malfunction or being in an alternate universe. And these humans and their societies show no sign of time traveling to the past. There was no doubt about it, they were on Earth 140 million years ago, and nearly every human subspecies had created all this.