The use of petroleum systems modelling (PSM) requires the integration of the geological sciences with petroleum engineering, physics and chemistry. In a recent paper in JPG (October 2014, vo. 37, pp 329-348), Mahanjane et al. (2014) applied a 1-D petroleum systems model to the study of maturation and petroleum generation in northern Mozambique. However, PSM cannot divorce itself from the fundamental laws of mechanics and thermodynamics when attempting to derive a thermal history to be used for the modelling of maturation and petroleum generation. As will be shown in this brief Comment, the application of mechanics and thermodynamics to the derivation of the thermal history may require some radical changes to the methods currently used in PSM. Mechanics and thermodynamics require a reducing heat flow during subsidence, but require an increased heat flow during inversion. The failure to apply mechanics and thermodynamics during thermal history derivation in PSM arises from a failure to incorporate the effects of pressure into the kinetic models used for predicting maturation and petroleum generation. Pressure increases the activation energy of endothermic reactions including maturation and petroleum generation in the kinetic model used to predict the reaction rate, and results in higher temperatures being required to produce the same transformation ratio as would be required for the current temperature - time kinetic models. Incorporating pressure should enable the same thermal history obtained from tectonic history-mechanic-thermodynamic models to be used as those used to calibrate the thermal history using maturity parameters such as vitrinite reflectance.