This question is both metaphysical and epistemological - that is to say, it's a metaphysical question about epistemology, or a meta-epistemic question.

Of course, this question also will depend on what you see knowledge as being. This not only includes the necessary and sufficient conditions (or lack thereof) for knowledge to be knowledge (i.e. epistemic essentialism), such as JTB+ or pick-your-favorite-epistemology, or but also how knowledge is. Why does knowledge exist?

So we have Socrates, in Plato's Theaetetus, debating the aforementioned philosopher on what knowledge is. Socrates pushes Theaetetus to accept that knowledge must be something more than just true belief - it must be justified true belief. And so this concept reigned for a while until other epistemologies started to crop up, culminating in the Gettier cases. But this is primarily epistemology proper - what knowledge is. What about knowledge's place in nature? Why does knowledge exist, and how?

Kornblith, for example, argues that knowledge is a natural kind, and thus suitable for empirical analysis and not conceptual analysis.

Then we have Plantinga with his Evolutionary Argument against Naturalism. In short: evolution is true, we have knowledge that evolution is true (in addition to other knowledge), naturalistic evolution would not select for true beliefs, therefore naturalism is false and God must have intervened sometime in the process of human evolution.

I have a number of issues with this argument. First, Plantinga assumes that naturalistic evolution cannot account for knowledge - but this is not entirely obvious. Second, Plantinga assumes that humans are in fact rational - his argument is meant to show that God exists because humans are rational - when in reality, humans are very much so irrational creatures, and you have to wonder (among other things) why God would make irrationality such a pervasive feature in his creations.

So Plantinga's argument for theism fails, but his argument in general does bring to light some interesting ideas: namely, why humans have knowledge, and more broadly speaking, why knowledge even exists. By knowledge I am loosely referring to any JTB+-like definition, as well as correspondence theory. Any other theory does not count as knowledge, in this case, because it's not relevant to the situation. And by and far, philosophy is the search for truth, and overwhelmingly truth is seen as correspondence theory and not some social construct or Rortian pragmatic choose-your-favorite-theory theory.

An obvious answer to why humans have knowledge, or why knowledge even exists, is that it was useful to us to have. But we need not be conscious to make use of stimuli. What use is conscious knowledge to the organism?

I think the thought of cultural anthropologist Ernest Becker has some relevance here:

A key point in a child's development is the recognition that other people have minds. Other people hold information just as the child does. Other people communicate and share this knowledge with each other, including with the child. But most importantly, other people withhold information. Other people deceive each other. The key moment in which a child learns that other people have minds is when the child learns that other people practice deception.

Thus, knowledge would be a very useful commodity in the social sphere.

Furthermore, as Heidegger noted, anxiety is a fundamental aspect of being a human. This anxiety is from not-knowing: just as we would have felt anxious when we didn't know what caused the stick in the forest to crack, we feel anxious when we don't know what happens after death, or where the universe came from, or why we're here, etc. In addition to pragmatic knowledge being sourced from a recognition of deception in the social sphere, it seems as though curious attempts at genuine correspondence truth is almost accidental, like a by-product of a hyperactive mind.

More needs to be said, though. Do our logical thoughts have a teleological nature - i.e. "aimed" at truth? Where does logic come from? Is knowledge a purely mental phenomenon, or is it an ontological relationship between things? How is that we are able to reflexively analyze our own beliefs? What use would philosophical thoughts have in the wild? Are they, as mentioned before, simply accidental features of a human being? Is there anything "special" about humanity's ability to reason, such as the Scholastic concept of the Intellect?

A point that I think might be important is that we probably shouldn't create this inseparable boundary between human minds and the rest of the world. If the world is logical, and humans are part of the world, then humans will be logical. This still has to account for the existence of illogical and irrational thoughts, though.