Evolution does not help Minsky's theory of a resourceful mind. Although he tries to frame his discussion in loose evolutionary terms in the Emotion Machine and the book it is based on: Society of Mind (here is a good review/summary). As you noted during your reading:
Minsky backs himself up by saying "evolution did so", but hasn't provided tests or studies that verify such claims
There are several reasons why he can't back himself up, and these are not unique to him but common throughout evolutionary psychology. The fundamental reason why Minsky (and other evolutionary psychologists) can't provide biologically convincing defenses for their evolutionary statements is because they are buildings theories of the mind, not the brain.
Biological evolution (at least in the modern synthesis) acts on genes. It is already hard enough to provide evolutionary descriptions on this level (see for instance issues surrounding the green-beard effect). However, biologists are sometimes able to go one step past this and start talking about basic physiology and the phenotypes and how selection acts on them. These are discussions about phenotypic traits. The traits that are most easily linked to the genes that express them are the ones that we can study effectively.
The brain is not easily linked to the genes that express it. Thus questions about the brain are already difficult enough to talk about from an evolutionary perspective (although some try). The mind is one more level of description higher up. Thus, in order to have a precise evolutionary statements about the mind we would need to solve the whole chain: genes --> protein expression --> physiology of the brain --> function of the brain --> function of the mind. We haven't solved any of these arrows, so it is not surprising that Minsky does not have hard evidence to support himself.
Lastly, when you read Minsky (and other evolutionary psychologists) be wary of teleological arguments. For us to have some trait doesn't mean that the trait needs to have been selected for at some point (in fact, some make a whole ruckus over what it even means to 'select for a trait'). Especially when you are considering such epiphenomena as the basic agents (or resources in the new book) of the mind. Take a look at genetic drift as a starting point.