A 2012 Discovery Networks video (Ѻ) of the current generic view of the so-called first "living thing”, which they present as a piece or fragment of (a) genetic material (brought to earth via a meteoroid), in (b) a chemical soup, that gets (c) “luckily”, by blind random chance, gets caught or contained (by accident) in an oily membrane, which then gets (d) struck by lightning, which then later (e) reproduces a copy of itself.
In science, living thing, as contrasted with a so-called ‘dead thing’, is a synonym for something deemed as being ‘alive’, often a term used in discussions of the origin of life—although, correctly, in the framework of the life categorized as a defunct theory (see: defunct theory of life), the modern physical science upgrade for ‘living thing’ is animate chnopsological bound state matter in any of various states of reactivity.

Overview
In 1809, German polymath Johann Goethe, in his Elective Affinities (P1:C4), wherein Charlotte asks the Edward about the book he is reading, refers to a living thing as follows:

“I am sure you will forgive me my fault,” she said, “when I tell you what it was this moment which came over me. I heard you reading something about affinities, and I thought directly of some relations of mine, two of whom are just now occupying me a great deal. Then my attention went back to the book. I found it was not about living things at all, and I looked over to get the thread of it right again.”

The book he was reading out of being a physical chemistry textbook (Torbern Bergman's 1785 A Dissertation on Elective Attractions, by implication, based on Goethe's 24 Jul 1809 comment); with the early 19th century suggestion that chemicals are not living things whereas people are living things; whereas, correctly, the early 21st century now sees the situation being only a false dichotomy, a carryover religious-mythology belief systems.

In 1997, Lee Smolin, in his The Life of the Cosmos, stated the following: [1]

“The entropy of a living thing is much lower, atom for atom, than anything else in the universe.”

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First living thing
See also: Ouroboros
Related, in respect to origin of life theories, is the hypothetical premise, historically, of the existence of a "first living thing".

See also
● Living being
● Living matter
● Living molecule
● Living organism

References
1. Smolin, Lee. (1997). The Life of the Cosmos (pg. 28). Oxford University Press.

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