This thinker analogized the phase transitions of water to explicate his law of "transition from quantity to quality" as a social evolutionary mechanism.
This thinker analogized the phase transitions of water to explicate his law of "transition from quantity to quality" as a social evolutionary mechanism. He speculated that the human brain evolved in conjunction with the transition from apes using their feet and hands for different purposes in an oft-excerpted section of a larger work titled "The Part Played by Labor in the Transition from Ape to Man." He used notes of a colleague on Lewis Morgan's Ancient Society to describe a four-stage development of the family, ending with "monogamous family." This author's unfinished work Dialectics of Nature developed ideas about science first articulated in the polemical attack "Prussian Vodka in the German Reichstag," which he expanded into a critique of a German philosopher's "revolution in science" titled Anti-Duhring. Another work was inspired by the high morality rates from disease in Liverpool and Manchester. FTP, name this social thinker who wrote The Condition of the Working Class in England and co-authored The Communist Manifesto with Marx. 
This thinker analogized the phase transitions of water to explicate his law of "transition from quantity to quality" as a social evolutionary mechanism.
Friedrich Engels 