Note in the quote below from a preface to Capital I, Marx remark would seem to indicate that he thought commodity exchange had existed for 2000 years already. Obviously, much of that was before capitalism. Anyway, commodity exchange/production impliedly has an origin ,and it is before capitalism. There is a qualitative distinction between the commodity production of capitalism and all previous modes of commodity production. This is probably the distinction Engels is making in referring to "simple commodity production. "
Also, Marx famously asserts that Aristotle had discovered the conceptual distinction between "use-value" and "exchange-value" ( to an extent limited by the fact that Aristotle lived in a mode of production in which slave labor was prominent , and therefore couldn't conceive of slave labor as equal to the labor of the free). This distinction is central to the schemes Marx sets out in the opening sections of _Capital_. The commodity production of Athens was "simple commodity production" in a historically _actual society_ ( the thing that Christopher Arthur doubts and criticizes in Engels in Arthur's essay linked in Richard Harris's post on this thread), simple relative to the more complex commodity production of the capitalist mode of production, in which labor power is a commodity and commodity production is the main form of production as opposed to confined to the periphery and intersticies ( like ___ (sic) in the intersticies of Polish society) in pre-capitalist society, to use Marx's metaphor.
Charles
"
Nevertheless, the human mind has for more than 2,000 years sought in vain to get to the bottom of it all, whilst on the other hand, to the successful analysis of much more composite and complex forms, there has been at least an approximation ."
Karl Marx Capital Volume One :1867 Preface to the First German Edition
clip-
Every beginning is difficult, holds in all sciences. To understand the first chapter, especially the section that contains the analysis of commodities, will, therefore, present the greatest difficulty. That which concerns more especially the analysis of the substance of value and the magnitude of value, I have, as much as it was possible, popularised. [1] <http://www.marxists.org/archive/marx/works/1867-c1/p1.htm#1> The value-form, whose fully developed shape is the money-form, is very elementary and simple. Nevertheless, the human mind has for more than 2,000 years sought in vain to get to the bottom of it all, whilst on the other hand, to the successful analysis of much more composite and complex forms, there has been at least an approximation. Why? Because the body, as an organic whole, is more easy of study than are the cells of that body. In the analysis of economic forms, moreover, neither microscopes nor chemical reagents are of use. The force of abstraction must replace both. But in bourgeois society, the commodity-form of the product of labour - or value-form of the commodity - is the economic cell-form. To the superficial observer, the analysis of these forms seems to turn upon minutiae. It does in fact deal with minutiae, but they are of the same order as those dealt with in microscopic anatomy