|1952, 209-page book The Next Million Years by English physicist C.G. Darwin, in the famous Introduction chapter (pgs. 13-28) of which he outlines "human thermodynamics", a subject he defines as the statistical mechanics of conservative dynamical systems of human molecules.|
In short, Darwin's book is first-ever published document outlining a theory using the terms "human thermodynamics" and "human molecule" in unison, as discussed in his 16-page Introduction chapter. 
The book was reprinted in 1953 and 1973. The Next Million Years is one of the founding books in the history of human thermodynamics.
The title of the book takes its name from C.G. Darwin's knowledge that it takes a million years for a new species to form.
In short, Darwin argued that humans were molecules, that assemblies of humans constituted "conservative dynamical systems", and that one could use statistical thermodynamics, particularly American mathematical physicist Willard Gibbs version of it, to predict the course of the next million years of human evolution.
In his book, according to a 1953 review by Time magazine, Darwin, a theoretical physicist, invades sociological territory where many sociologists fear to tread.  He bases his reasoning about man's future on what is sometimes called "social physics": the idea that the behavior of humans in very large numbers can be predicted by the statistical methods that physicists use with large numbers of molecules.
Accordingly, in the gas phase, the motions of single molecules are unpredictable: they may move fast or slow and zigzag in any direction, but the impacts of billions of gas molecules against a restraining surface produce a steady push that obeys definite and rather simple laws. In the same manner, Darwin believes, the actions of individual humans are erratic and sometimes remarkable, but the behavior of large numbers of them over long periods of time is as predictable as the pressure of gas. All that is needed is to determine the basic, averaged-out properties of human "molecules."
In Darwin's view, according to the review, "human molecules have one fundamental property that dominates all others: they tend to increase their numbers up to the absolute limit of their food supply". 
The book, as of 2010, seems to be out of print and the in demand original copies sell for as much as $395 dollars.
1. Darwin, Charles G. (1952). The Next Million Years (chapter one) (Scribd). London: Rupert Hart-Davis.
2. Staff Writer. (1953). “Million-Year Prophecy”. Time, Monday, Jan. 19.
● Jessop, Brent. (2008). “A Darwin’s Look into The Next Million Years” (four part review), March 3. Knowledge Driven Revolution.com
● Bates, Marson. (1954). “Reviewed work: The Next Million Years by Charles G. Darwin.” American Anthropologist, New Series, Vol. 56, No. 2, Part. 1. Apr. pg. 337.
● Green, Howard. (1954). “Book Review: The Next Million Years”, Bulletin of the Atomic Scientists, pgs. 55. Feb.
● The Next Million Years – Infowars.Wikia.com.