To test a fundamental hypothesis of ecological-evolutionary theory, that technical and economic heritage affects current rates and patterns of development, Third World societies were classified as “industrializing agrarian” or “industrializing horticultural” on the basis of their dominant subsistence technologies prior to sustained contact with industrial societies and industrial technology, and then compared on five basic dimensions: (1) current levels of technological and economic development, (2) informational resources, (3) rates of economic growth, (4) vital rates, and (5) trade dependency. Predicted differences were found on all dimensions. Alternative explanations were explored and rejected, and it was also demonstrated that these differences were not explained by network position in the world economy or by recency of national independence. These findings suggest that the impact of techno-economic heritage on development merits further investigation.