The first two series have a definite bias towards humans, in that the very first and earliest episode shows a few early crustaceans before focusing in on the most seemingly insignificant little worm, which is of course the first vertebrate. Narrator Kenneth Brannagh constantly reminds that this or that humble creature is destined to spawn class mammalia. It's prehistory written by the winners. There are in addition several themes which crop up throughout the two series, the most recognizable of which are
- Complex behaviors like nest guarding, parental care, social cohesion and cooperative hunting developed slowly and independent of each other. The series thus tends to focus on first instances of these things (the first australopithecus clan defending a weaker member as a group springs to mind), but that's not always the case, as in the most memorable iteration of this theme, in which a dimetredon that has violently defended her nest nearly to the point of death immediately ceases to defend her offspring upon hatching and in fact attempts to eat some of them. The point, which is well taken, is that it is not the case that one day niceness just evolved up out of nowhere, and that the suite of adaptations that we humans consider to be either honorable or uniquely human all exist for some logical reason.
- The hunter becomes the hunted, on a ridiculously regular basis. The series positively revels in apocalyptic death beasts evolving into prey. Case in point, did you know that the ungulates (hooved mammals including cows and pigs and sheep and goats) were originally carnivorous, and that the only descendants of that group to still be carnivorous are the cetaceans (whales and dolphins)?
- The story of evolution is not a straight line, and the development of certain killer adaptations can re-write the course of it. The series cites the sense of touch in early invertebrates, the abovementioned complex behaviors, walking on hind legs and speed and agility in early dinosaurs and walking on hind legs in humans. The series also goes out of its way to suggest that mammal-like reptiles were the kings of the earth before the dinosaurs appeared, and that essentially the dinosaurs sort of stole the throne for one hundred and change million years but in the end they died out and we took our rightful place. It's sort of fatalistic in that way.
- If there had been cameras and nature photographers in ancient prehistory, animals of all periods would have shown a great interest in them. The camera in both series is constantly being hit, nudged or broken by herds, fights, etc. It's verite in that same way that the debris from the exploding Cloud Nine on Galactica hit the camera.
- Climate rules everything. Climate (and oxygen levels) can turn insects huge, kill off dinosaurs, give rise to grass and thus create whole new categories of grazing animals, change whales from hunters to filter feeders and basically just trump whatever is going on evolutionarily. Certainly no fault to be found with this view.
- We are destined to kill every animal that cannot live in a human-scaled world. No matter how hard we try to save the whales and the pandas and the elephants, they are doomed, because we have already killed 90% of the large animals that existed when we evolved, not by hunting them (the series claims we didn't hunt mammoths at some point because they were too huge and dangerous) but by simply making their lifestyle unsustainable.
The two series are great because they highlight incredibly interesting periods in the Earth's history that often go overlooked in favor of dinosaurs. They undoubtedly oversimplify and tend to favor flashy minority opinions, like that some 200 million year old hunter used venom to kill its prey.