In short, partially. Walking with Beasts is a prehistory-related television documentary that's over a decade old, and this much time has the unfortunate effect of rendering the CGI and animatronic reconstructions of its dinosaurs and other prehistoric creatures highly obsolete and unscientific. The field of paleontology advances in a staggering speed, meaning that even documentaries that are merely a year or two old tend to get quickly dated. Another problem that factored in was that in a lot of cases, the production crew purposely decided to make their creatures unscientific (or at least scientifically implausible) due to budgetary reasons, or for sheer sensationalism. At the very least, the production is far more accurate than its predecessor Walking with Dinosaurs
As for a less than exhaustive list of the more prominent errors:
* Gastornis is depicted as a fearsome predator that terrorized smaller animals. Modern research suggests that this interpretation has no basis, instead, the animal was almost certainly fully herbivorous.
* Eurotamandua is live-acted by a modern-day tamandua. It probably belonged to afrotherians (like aardvarks or elephant shrews) rather than xenarthrans (like anteaters), although it could be argued that it still looked somewhat like a tamandua.
* Leptictidium moving around by hopping has been called into question.
* Although pointed out by the narration, Ambulocetus isn't known from Europe. It also had an upright gait and it is doubtful that it hunted like crocodiles.
* Propalaeotherium, although related, was probably not ancestral to modern horses.
* Basilosaurus was probably at home in shallow water, not open sea as the show claims.
* Both sexes of Embolotherium (called brontotheres in the episode) probably had a heart-shaped crest, not just the males.
* Andrewsarchus is no longer believed to have been a relative of whales, being instead similar to the entelodonts from episode 3.
* Hyaenodon's teeth were more suitable for shearing than crushing.
* Deinotherium's anatomy has been criticized by some people, mostly because its trunk is entirely too short.
* DInofelis probably didn't hunt human ancestors, going for grass-eating herbivores instead.
* The series' depiction of Phorusrhacos is more in line with a similar bird, Titanis. Phorusrhacos was smaller and has been extinct for almost 20 million years before the time of the episode it's featured in.
* Smilodon is presented as having lived and hunted like modern-day lions. This is highly speculative and most likely false. Their hunting strategy, which involves them running down their prey over long distances, is certainly incorrect, since Smilodon's bulky anatomy meant that it was a horrible runner.
* Although plausible, given that almost every animal, even herbivores, eat meat to supplement their diet, the meat-eating Megatherium is speculation.
* Cro-Magnon people had darker skin.
* Neanderthal wasn't the only species of human living besides the Cro-Magnons in episode 6. There was also Homo floresiensis, though they are known from a different area of the world (Indonesia) than where the episode takes place in (Northern Europe).
* Some think that the notion of Neanderthals pushing mammoths off cliffs has been based on misinterpreted evidence.
* The coloration on certain Ice Age mammals is probably incorrect, if cave paintings depicting these are to be believed.