In hmolscience, James J. Elser (c. 1959-) is an American evolutionary ecologist and limnologist noted, in human chemistry, for his 2000 Sterner-Elser human molecular formula.
In 2000, Elser, together with Robert Sterner, calculated the following 22-element human molecular formula:
H375,000,000 O132,000,000 C85,700,000 N6,430,000 Ca1,500,000 P1,020,000 S206,000 Na183,000 K177,000
Cl127,000 Mg40,000 Si38,600 Fe2,680 Zn2,110 Cu76 I14 Mn13 F13 Cr7 Se4 Mo3 Co1
They published the result in their 2002 book Ecological Stoichiometry: the Biology of Elements from Molecules to the Biosphere. This amounts to a 22-element human empirical molecular formula.  A similar 26-element empirical molecular formula calculation was made by American chemical engineer Libb Thims also in 2002. 
They conclude “this formula combines all compounds in a human being into a single abstract ‘molecule’”. They continues, “our main purpose in introducing this formula for the ‘human molecule’ is to stimulate you to begin to think about how every human being represents the coming together of atoms in proportions that are, if not constant, at least bounded and obeying some rules”.
They state that ecological stoichiometry is about “how chemical elements come together to form evolved, living species in ecosystems.” The abstraction followed in this science, according to Sterner and Elser, is that “organisms can be thought of as complex evolved chemical substances that interact with each other and the abiotic world in a way that resembles a complex, composite, chemical reaction” and that “ecological interactions invariably involve chemical rearrangements”. In summary, they state that “like any other normal chemical rearrangement at the surface of the Earth, when organisms interact, mass must be conserved and elements are neither created nor destroyed.” Moreover, “there is stoichiometry in ecology, just as there is in organic synthesis in a test tube”.
Elser completed his BS in biology from the University of Notre Dame in 1981, his MS in ecology from the University of Tennessee in 1983, and his PhD in ecology from the University of California, Davis, in 1990.
1. Sterner, Robert W. and Elser, James J. (2002). Ecological Stoichiometry: the Biology of Elements from Molecules to the Biosphere, (chapter one), (pg. 3-7, 47, 135). Princeton: Princeton University Press.
2. (a) Thims, Libb. (2008). The Human Molecule, (preview). Morrisville, NC: LuLu.
(b) Molecular Evolution Table - Institute of Human Thermodynamics.
(c) Thims, Libb. (2007). Human Chemistry (Volume One), (preview), (ch. 2: "The Human Molecule", pgs. 15-35). Morrisville, NC: LuLu.
● Elser, James J. and Hamilton Andrew. (2007). "Stiochiometry and the New Biology: The Future is Now," PLoS Biol, Vol. 5(7), July.
● James Elser (faculty) – Arizona State University.