For years campaigners have asked parents to avoid toys they say promote gender inequality.
But some baby baboons, in a new documentary by the BBC and Offspring Films, may have proven that "boys' toys" and "girls' toys", do really exist.
Animals at Play is said to explore the very reasons why creatures play together.
A statement from the BBC said in one of the documentary's experiments, a troop of baboons are given some toys to play with.
"This test sheds light on an age-old question that surrounds human behaviour: are males and females biologically programmed to play in different ways, or are the differences that we see a result of social influences from parents and peers?"
The BBC says the results are "striking". Female primates are seen playing with dolls, while the males play with trucks, "suggesting that there is an innate component to play".
"Play is so much more than just fun and games," Offspring executive director Alex Williamson told realscreen.com.
"It's fundamental to an animal's development and in some cases, its survival."
Campaigners in the past have said promoting guns and action figures for boys, and dolls and crafts for girls is archaic and can alienate children. They suggest gender-specific colours are also harmful.