In life thermodynamics, local entropy decrease is a postulate that living organisms represent an increase in order and thus effect a local decrease in entropy, a term assumed to be equivalent to disorder, in the context of the universe; and it is argued that this decrease in local entropy runs on either a greater increase in entropy in the surroundings or on energy from the sun. [1] This oft-repeated postulate seems to have been introduced in 1947 by Belgian-born English thermodynamicist Alfred Ubbelohde. [2]

Ubbelohde's synthesis
This logic of life equating to local entropy decreases seems to have been first introduced in the 1947 book Time and Thermodynamics, section “Experimental Aspects of the Relation between Thermodynamics and Life”, by Belgian-born Engish thermodynamicst Alfred Ubbelohde, an Oxford professor of thermodynamics. [3] In particular, Ubbelohde argued that living organisms have a “disentropic behavior” or a behavior opposite to that of entropy. In more detail, building on the hypothesis of Scottish physicist James Maxell’s 1867 thermodynamic “demon”, where it is argued that to evade the second law the demon, at the doorway to a two-compartment system of gas molecules, one hot, one cold, would have to “select” all the faster moving molecules from the mixture to effect a cold to hot heat transfer, Ubbelohde states that:

“If Maxwell’s idea of selection applies in some form to living organisms, we might expect their behavior to be completely disentropic, and within a closed system containing living organisms there might be a net decrease in entropy, in the course of time.”

In contrast to this proposal, Ubbelohde outlines a second proposal, which he favors:

“Living organisms are characterized thermodynamically not by any vital power of selection of individual molecules, but by the fact that the organism considered as a unit is continually effecting processes, in which the entropy decreases, at the expense of rather greater compensating increases of entropy in the surroundings.”

Moreover, he states that living beings are “parasites on the entropy fund of the universe.” On this basis, he states:

“Living things would be so organized to effect local entropy decreases continually, so as to direct molecular processes to specific ends; this activity would, however, depend on appropriate food supplies, since it would be the conversion of food-stuffs into waste matter with higher entropy content that would compensate for the entropy decrease associated with specific behavior, and that would, on balance, give a net increase of entropy.”

In conclusion, Ubbelohde notes that further experimental tests will be needed to determine which of the two scenarios, i.e. Maxwell’s selection method (organisms being absolutely disentropic and swim upstream in the main current of entropy) or the local entropy decrease method (organisms being regions of local entropy decrease moving upstream by skilful use of local eddies within the current), is to be the explanation of the behavior of living organisms.

Other views
In 1950, American biologist Harold Blum stated: [6]

“Since any increase in order within the biosphere must be very small compared to the increase of entropy in the sun-earth system there is no reason to think that evolution controverts the second law of thermodynamics … local parts of the system may for a time increase in order.”

In 1950, American mathematican Norbert Wierner stated a near-similar version: [5]

“Life … represent[s] pockets of decreasing entropy in a framework in which the large entropy tends to increase.”

In 1963, American physicist Robert Lindsay parlayed the concept of “local” entropy effects into a theory of local “entropy consumption”. In particular, Lindsay states: [3]

“Local consumption of entropy is not to be considered a genuine violation of the second law, for it seems altogether likely that the entropy consumption of living things is compensated for by the corresponding entropy production elsewhere in the universe.”

In another 1964 sense, professed by English scientist James Lovelock, during the time when NASA had begun to make plans to look for life on Mars, a “reversal” or “reduction” in entropy was postulated to represent a sign of life in the universe; supposing, for instance, one were to build life detection equipment to look for life on other planets. [4]

Difficulties on theory
The concept of: "Local decreased in entropy = Life", as it is commonly used, however, seems to be an entropology-like argument culled from a crude extrapolation of Maxwell's demon logic, the idea of material entropy, and a mix of the disorder views of entropy professed by Austrian physicist Ludwig Boltzman in his gas theory. In this view, the term does not seem to be a rigorious one, in the chemical thermodynamics sense of a person being a "human molecule", and may in fact be non-logical. In a more logical sense, the entropic relations involved in surface thermodynamics would be a more logical branch of thermodynamics to cull from over that of statistical thermodynamics of gas-phase particles.

See also
● Entropy reduction
● Second law (disordering) evolution (ordering) reconciliations

References
1. Tobin, Allan J. and Dusheck, Jennie. (2004). Asking About Life, (pg. 516). Brooks Cole.
2. Ubbelohde, Alfred René. (1947). Time and Thermodynamics, (section “Experimental Aspects of the Relation between Thermodynamics and Life”, pgs. 100-05). Oxford University Press.
3. Lindsay, Robert B. (1963). The Role of Science in Civilization, (section: "Information Theory and Thermodynamics: Entropy", pgs. 153-65; section: "A Scientific Analogy: The Thermodynamic Imperative", pgs. 290-98). Westport: Greenwood Press. Dowden, Hutchinson & Ross.
4. Lovelock, James. (1979). Gaia - a New Look at Life on Earth. Oxford: Oxford University Press.
5. Wiener, Norbert. (1950). The Human Use of Human Beings; Cybernetics and Society, (pg. 32). Boston: Houghton Mifflin Co.
6. Blum, Harold F. (1951). Time's Arrow and Evolution. Princeton: Princeton University Press.