I think that differences in climate is one key factor but I think it could be explained by David Ricardo's theory on international trade differences???
The key is production capabilities, not relative specialization. In words of Hausmann and Rodrik (2006):
The idea that rich (poor) countries tend to export goods exported by other rich (poor) countries is quite obvious and is compatible with many possible theories. For example, in conventional trade theory a la Heckscher-Ohlin, countries export products that are more intensive in the factors of production that are relatively abundant at home. As development takes place, physical, human and institutional capital is accumulated and the products countries export become more intensive in these factors. ...
Labor-abundant countries trade with land- or capital-abundant countries in order to acquire more efficiently the goods that are intensive in the factors they don’t have. The transition between goods is of little significance: they are the passive consequence of changing factor endowments.