I would suggest that Arnold Kling (and Tyler Cowen) read (if they have not yet done so) Morris Silver’s, Economic Structures in Antiquity’ (Greenwood Press, 1995), which also includes his studied demolition of Karl Polanyi’s thesis that markets did not exist until the mid-19th century (originally published in the Journal of Economic History, 1983). Silver also wrote other articles and books that demonstrate the prevalence of the ‘propensity to truck, barter, and trade’ across the classical world and long before.
My own research (unpublished) on the ‘Pre-History of Bargaining’ supports Adam Smith’s speculative assertion on the longevity of the said propensity, and its earlier evolution from teamwork for unequal shares of meat from kills to reciprocity behaviour (what I call quasi-bargains) evident not just among humans –and presumably the hominids before them – and in the behaviours of primates.
I am reading just now a most valuable book bordering on these issues, edited by Paul J. Zak, Moral Markets: the critical role of values in the economy (Princeton University Press), which develops themes contributing to an understanding of the social-evolutionary importance of humans establishing the criteria by which fairness and unfairness is mediated in primate and human relationships.
Now most economists reading Blogs by other economists would never dream of reading such material (the maths is minimal), but if they did it would inform them of greater depth in what they think they are doing practicing economics they way we do now.