Theodosius Dobzhansky (1900-1975) was a very influential geneticist and one of the architects of the modern synthesis of genetics and evolutionary biology; I heard that he also liked to make French-toast for breakfast. He is in my academic lineage as my Ph.D. advisor's advisor's advisor's advisor---sort of my academic great-great-grandfather.
There is a famous essay he wrote in 1973 that is widely quoted and referenced; "Nothing in Biology Makes Sense Except in the Light of Evolution" (The American Biology Teacher 35:125-129). This is repeated over and over in the literature, grant applications, department and lab websites, and class teaching materials, etc., dare I say it, ad nauseum (e.g., Varki, A. (2006). Nothing in glycobiology makes sense, except in the light of evolution. Cell, 126(5), 841-845; Valas, R. E., Yang, S., & Bourne, P. E. (2009). Nothing about protein structure classification makes sense except in the light of evolution. Current Opinion in Structural Biology, 19(3), 329-334; Seyfried, T. N. (2012). Nothing in cancer biology makes sense except in the light of evolution. Cancer as a Metabolic Disease: On the Origin, Management and Prevention of Cancer, 261-275).
However, there is odd and little known historical detail behind this that Fred Gould (NCSU) pointed out to me in a conversation we had last year. Almost 10 years before, in 1964, Dobzhansky published an address entitled "Biology, Molecular and Organismic" (American Zoologist 4:443-452). If you scan through it there is a familiar line in an unfamiliar context (p. 449) "I venture another, and perhaps equally reckless, generalization---nothing makes sense in biology except in the light of evolution." To put this into perspective, in the article he is arguing against a reductionist hierarchy in science, "the proposition that chemistry and physics are sciences more 'advanced'" and that "the aim of biology is, then, to describe life in terms of first of chemistry, and eventually of physics." Dobzhansky goes on to argue that biology should proceed on two fronts, one a mechanistic reductionism and another that studies higher order emergent properties of the evolutionary process. "Both the mechanistic and evolutionary explanations are pertinent to, and are made use of, in molecular as well as in organismic biology. These explanations are not alternative or competing; they are complementary, without, however, being either deducible from or reducible to each other. ... To treat molecular biology instead as a bludgeon with which to destroy, or to reduce to insignificance, the organismic biology is to basically misunderstand the nature of life."
So, Dobzhansky first made the statement "nothing makes sense in biology except in the light of evolution" as an example of an argumentum ad absurdum, a ridiculous extreme that was not true. Rather, he seemed to intend that not everything in biology makes sense when only considering evolution or molecular biology independently; they must be both considered together for a more realistic understanding of biology. Evolution does not do a good job of explaining hydrogen bonding between two DNA strands, chemistry does; yet, this understanding is needed to work with DNA in the lab and better understand how genetic inheritance works, which is squarely biological. Conversely, neither chemistry nor physics can even begin to explain why we have nonfunctional remnants of a gene (GULO, a.k.a, GLO and GULOP in humans) involved in vitamin C synthesis on our eighth chromosome (e.g., Drouin, G., Godin, J. R., & Pagé, B. (2011). The genetics of vitamin C loss in vertebrates. Current Genomics, 12(5), 371; Helliwell, K. E., Wheeler, G. L., & Smith, A. G. (2013). Widespread decay of vitamin-related pathways: coincidence or consequence? Trends in Genetics, 29(8), 469-478). Chemistry and physics tells us it is there, but how did it get there? Neither one nor the other views are complete. Biological evolution proceeds with what it has to work with, including the opportunities and constraints provided and imposed by chemistry and physics as well as other aspects of biology itself (such as existing gene interactions, behavior, and anatomical patterns---famous examples being the panda's "thumb," and the giraffe's recurrent laryngeal nerve).
In this light it is odd that Dobzhansky then used the statement as the title of his 1973 essay, without the balanced arguments made earlier. The line then became famous and his earlier address faded into obscurity. I guess it goes to show that to be successful it often pays to make an extreme and simple statement rather than a more accurate and complete statement. "Nothing succeeds like success" (Dobzhansky 1964).