In science, sex is a transformative process of field particle mediated atomic exchange. [1] In human chemical terms, sex can be described in terms of chemical mechanism. Sex can also be described in terms of energy, entropy, and thermodynamic driving forces.

Thermodynamics
Sex can be quantified thermodynamically. One of the first to discuss "sex" in relation to thermodynamics were American authors biologist Lynn Margulis and her son, science writer Dorion Sagan, who in their 1997 book What is Sex?, argue that sex, or specifically sexual reproduction, is “a byproduct of thermodynamic dissipation.” [2] They give the view that sex as has a “thermodynamic background”, in that the process of coupling is a crucial part of the energy transformation process by which (with pleasure) beings reproduce their forms and increase their complexities. In the construct of the earth system, Margulis and Sagan state, through sexual reproduction, animals evolved and mate selection began, wherein organisms, choosing some mates over others, played a role in their own evolution. [2] In reference to forces, they state that:


From a physics point of view, however, the force of sex is not a mystery and can be explained through a number of perspectives; namely through the fundamental forces of the universe (strong nuclear, weak nuclear, electromagnetic, and gravitational) and their quantification as exchange forces, in the dynamics of the interaction and in the construct of the human chemical bond, and thermodynamic forces, in the bulk driving forces of the system.

In the 2005 book Into the Cool: Energy Flow, Thermodynamics, and Life, American authors science writer Dorian Sagan and ecological thermodynamicist Eric Schneider argue that “sex is the way living dissipative systems propagate into the future” and that “sex maintains our form of thermodynamic disequilibrium by reproducing physiological systems much like us but newer and sometimes improved.” [3]

References
1. (a) Thims, Libb. (2007). Human Chemistry (Volume One), (preview), (Google books). Morrisville, NC: LuLu.
(b) Thims, Libb. (2007). Human Chemistry (Volume Two), (preview), (Google books). Morrisville, NC: LuLu.
2. Margulis, Lynn and Sagan, Dorion. (1997). What is Sex? New York: Simon & Schuster.
3. Schneider, Eric D. and Sagan, Dorion. (2005). Into the Cool - Energy Flow, Thermodynamics, and Life, (section: Sex and Thermodynamics, pgs. 154-55). Chicago: The University of Chicago Press.