It may be a metaphor in a way alluding to the behaviour of a system. Or it may be literal. We might also say "programmed".
If you think about the brain or the body in general, especially the nervous system, it resembles a network of connections, with signals travelling along them, supposedly causing our actions. An evolutionary sociobiologist might say we are wired as humans to especially be altruistic towards our kin. This might be metaphorical if alluding to the way an electronic circuit is wired to perform different things like making a light flash or turning a motor. Here is a picture of ENIAC, an old computer in the 1940s. Notice the cables (for the record, I don't know if those wire-looking things are cables or vacuum tubes). Each program would require changing the positions of these cables if you wanted to program something, like say, calculate artillery trajectory.
In the literal and physical sense it's correct also because we have hundreds of billions of neurons which allow us to move and speak and think and generally act, the formation of which are encoded in or "programmed" by our genes, and influenced also by our environment too. On the topic of genes, the expression "Not in one's genes" colloquially means "not in one's nature."
Also, confer the expression:
get one's wires crossed
Also, have one's wires crossed. Become or
be confused or mistaken about something, as in If you think there's a
meeting today, you really have your wires crossed; it's not till next
month . This expression transfers a wrongly wired telephone or
telegraph connection to human misunderstanding. [Colloquial; early
1900s]
American Heritage Dictionary
So here's another metaphor about wires being wrongly arranged leading to mental quirks.
Also, an article from the BBC
Brains may be wired for addiction
The topic of the article is that some brains may cause certain individuals to be predisposed to becoming addicted.