Ability to use symbols appeared 35 million years ago?

Humans are sometimes said to be distinguished as "The Symbolic Species." A Research Highlights note in Nature point to the work of Addessi et al., who show that capuchin monkeys, who diverged from the human lineage ~35 million years ago, can be trained to use and assign value to tokens (symbols) for different items of food.

...Elsa Addessi of the CNR, Italy's national research council, and her colleagues trained five monkeys to associate a particular token — such as a green chip, black plastic tube or a brass hook — with one of three specific types of food. They then gave the monkeys a series of choices, each time between different amounts of two food items or between two types of token...The value the monkeys assigned to a token was very similar to the value they gave to the food it represented, which suggests that the animals weighed up both real and symbolic options in an equivalent manner.