The major transitions of evolution required the emergence cooperation amongst the lower-levels of selection. Many mathematical models have uncovered sufficient conditions for the evolution of cooperation amongst selfish agents but within this framework there are as many plausible scenarios which lead to cooperative outcomes as there scenarios in which defection prospers. A new approach to explaining reciprocity appeals to the same mechanisms which have systematically enabled an explosion of reciprocity and welfare in human societies, viz. markets. The field of biological markets conjectures that Adam Smith’s “invisible hand” is a universal phenomenon of nature rather than a parochial artefact of human societies. In this paper I review this field and speculate how an understanding of the role of market interactions in nature can explain the major transitions in evolution and the corresponding explosive increase in the complexity of life.