What has allowed humans to get continuously better at collective learning?

Symbolic language

Explanation:

Collective learning is the human ability to educate and teach one another, and gain knowledge and achieve goals together. The ability to develop and to get better at collective learning has come first from language and intelligence, and later from what is known as “symbolic language”

Symbolic language is the human ability to imagine, represent, and communicate various concepts and ideas. This kind of interaction is particular to humans and allows us to understand and convey ideas, concepts, feelings, and emotions that are not directly stated. Through symbolic communication, we can use various symbols and metaphors to represent different meanings, and the person to whom we communicate will understand them.

As this complex communication got better and more developed, people could represent ideas more, and, therefore, get better at collective learning.

the government paid religious orders to provide basic education to native american children on reservations. in the late 19th and early 20th centuries, the bureau of indian affairs (bia) founded additional boarding schools based on the assimilation model of the off-reservation carlisle indian industrial school.