Astro Boy: Tetsuwan Atom - episode 39 - 10 Jan, 2004

Hunters from the future world collect superior animals in order to genetically manipulate them to create stronger creatures. After collecting the nearly extinct cheetah, the hunters now head to a world 10,000 years in the past to collect the mammoth. Atom and Uran get caught up in the hunt and are both transported 10,000 years back in time. The scenery of 10,000 years ago spreads before their eyes. Uran, who arrived there before Atom, is surrounded by hyenas and is in danger, but then a primitive boy appears and saves her. The boy doesn't speak their language, but Atom and Uran gradually get along with him, and a timeless friendship grows between the three of them. At the same time, the hunters continue mammoth hunting, taking along fellow monsters, Cyclops and Web. When Atom hears the sad cries of a baby mammoth, he sets out to rescue them. (Source: Wikipedia)