Reproduction, Natural, Voluntary

According to Smith, the propensity to barter is the distinguishing human characteristic, while for Smith, it is the use of tools. However, the latter is seemingly not related to Dialectical Materialism. In contrast, another example of a distinctively human activity that is directly involved with Dialectical Materialism is the modification of the reproductive process--rhythm methods, fertility drugs, contraception, pregnancy termination, etc. Given that immutable biological laws govern the process of conception itself, these basic examples demonstrate that a "voluntary" activity is always ultimately a modification of some "natural" core, and suggest that the distinction between the two is fundamentally that of Species to Genus, respectively.