Tom Hebert: 2 books

A few million humans are isolated on a earth-like planet. They occupy a continent that has an ecosystem that is identical to North America of 100,000 BC, complete with Wooly Mammoths and Saber Toothed Tigers. They have just discovered that other, alien races also inhabit the planet and that these...

this is a sequel to "a small glass container." a large, isolated group of humans have established two nations on an alien world and have survived wars with two alien species. the problem is that five different species of intelligent aliens on the planet and most shoot first and never ask questions.