The sabre-tooth cat and the short-faced bear were made with computer animations as well as animatronics. A dead mammoth was also built.
The shot of a bison being killed during a stampede is used three times. First, it is seen when the Smilodon ambushes the herd and takes down one of the bison. It is seen twice more during the buffalo slaughter at the end, it is clearly the same scene, although the background is different and is without the sabre-tooth. There is one shot that is exactly the same, and the third time during the massacre scene is flipped and zoomed in to look like it is different.
The footage of a lion was not just used to present an American Lion. Some footage from a similar documentary was used to portray the Smilodon, which is seen with similar coloring patterns to that of a lion. The Lioness's eyes, paws, and teeth are the clips that were used to create a Smilodon. This is only seen right before audiences actually see the Smilodon hunting the bison. The rest of the animal is portrayed with animations and an animatronic.
There are many clips from BBC and Discovery Channel's collaborative documentary series called "Wild New World" in the UK, and "Prehistoric America" in the US. Examples of recycled footage includes: Musk Oxen, Dall Sheep, Saiga Antelope, Camelops, Horses one clip of Smilodon (roaring atop a hill) and some footage of an American Lion.
The Clovis child whose remains are found in the beginning are based on the Anzick-1 fossil site. Here the child is a girl while the real specimen was a young boy.