How do we know so much about the Mississippian Indians?

Maize-based agriculture. In most places, the development of Mississippian culture coincided with the adoption of comparatively large-scale, intensive maize agriculture, which supported larger populations and craft specialization. ... This is the belief system of the Mississippians as we know it.

Explanation:

That's how we know so much about it.

the use of electrical signals that transit messages is know as

answer; strength of association;