The intellectual partnership of Allen Newell and Herbert Simon began at the RAND corporation in the early 1950s and became one of the most fruitful collaborations in the cognitive sciences. In 1975 the Assocition for Computing Machinery (aka the ACM) awarded them the A. M Turing Award, which is "given for major contributions of lasting importance to computing." Here's the full text of their acceptance speech: Computer Science as Empirical Inquiry: Symbols and Search (PDF).
And here's one of the core assertions of that paper (p. 116):
The Physical Symbol System Hypothesis. A physical symbol system has the necessary and sufficient means for general intelligent action.
The paper is important and influential. You should read it. (I've not done so yet, but it's on my stack).
A great deal of work in the cognitive sciences has been done under the assumption, sometimes explicit, sometimes tacit, that symbol processing is a primitive (or fairly primitive) process of nervous systems. For my part, I do not think symbol processing is primitive to nervous systems. Jellyfish have neurons, but those neurons don't process symbols. Nor do fish, bears and monkeys process symbols. I suspect that natural language is the simplest existing physical symbol system created without the deliberate design by human agents.
Near the end of their lecture, Newell and Simon state (p. 125):
Symbol systems are collections of patterns and processes, the latter being capable of producing, destroying and modifying the former. The most important properties of patterns is that they can designate objects, processes, or other patterns, and that, when they designate processes, they can be interpreted. Interpretation means carrying out the designated process. The two most significant classes of symbol systems with which we are acquainted are human beings and computers.
I note that human beings have created computers through deliberate design and, further, that it took millennia of cultural evolution to produce both the conceptual and physical devices equal to the task.