Most people think of humour as something that exists for the sake of entertainment, or for adding spice to social occasions.
But humour is an aspect of the human mind, and as such, is almost certainly part of a system for information processing. So what sort of information is being processed when we laugh at something funny?
Most humour follows a pattern like this:
And at the end of this process, we feel pleasure.
Most people are uncomfortable in situations that cause them to question the fundamental beliefs that they have about the world around them. If evidence seems to contradict that fundamental belief system, they will prefer to ignore the evidence rather than change their beliefs. They prefer not to consider even the possibility that they may be wrong.
Does this mean that people are just not open-minded enough? The mental strategies that we all follow have been finely tuned over millions of years of evolution, so they may be more sound than they seem at first. After all, if your fundamental beliefs are right, then ignoring evidence that undermines them is a sound strategy, because the evidence must be wrong. And if the fundamental beliefs are wrong, eventually the evidence against them will become overwhelming, and at that point we will happily (or at least grudgingly) change our beliefs anyway.
Letting all available evidence affect one's world view may be a recipe for disaster, because one can end up with no fundamental beliefs at all, which will lead to an inability to make decisions about what to do next.
What does this have to do with humour? As I mentioned initially, a careful analysis of humour shows that it has to do with being wrong about something. And the pleasure of humour contrasts with the mental unpleasantness of being wrong in situations which are not humorous. In fact one could presume that maybe the purpose of humour is precisely to cancel out the unpleasantness caused by confronting evidence that undermines our existing belief systems, at least under certain circumstances. And those certain circumstances are when the evidence against our beliefs is so overwhelming that there is little risk in accepting we were wrong in that particular case. In fact the pleasure of humour even encourages us to actively search out evidence that we may be obviously wrong about the things we believe in. For example we might seek the company of other people who can make us laugh.
In summary: we do not enjoy being presented with evidence that shows we might be wrong, but we do enjoy being presented with evidence that shows that we really, really are wrong.
If someone lacked a sense of humour, we would expect that person to have difficulty abandoning their existing belief systems, even when presented with very strong evidence against them.
When a social group is defined by a belief system, the members of the group have to tread carefully when it comes to humour. On the one hand humour plays a role in making social interaction more pleasant, and part of the pleasure of religion is the social interaction with others in the group. But on the other hand, the wrong sort of humour could threaten the group's belief system. Certain jokes are off-limits, or will be considered to be "not funny".
There is no strong evidence that I am aware of that non-human animals have anything quite like the human appreciation of humour. Of course much humour is language-based, so it is hard to know for certain if an animal without language has a sense of humour or not. If humour is a human peculiarity, then it must have evolved at some time after the last common ancestor of humans and their nearest living relatives.
Because humour does relate to belief systems, and belief systems themselves are largely detemined by language interactions in a social group, it is likely that humour has evolved after the development of language, and perhaps after the development of belief as a social activity. Developing belief as a social activity made it easy for whole societies to experiment with new world views and life strategies in the medium term. The downside would have been when socially defined beliefs started to become far removed from common-sense reality. Humour would then have been an important mechanism to curb these excesses.
At the same time humour plays an important role in the individual's development of their own personal belief systems. A lot of humour is derived from communication via language with other members of one's society. In effect members of a social group are seeking to successfully challenge each other's belief systems, as a result reducing each other's glaring errors.
Unfortunately humour does not leave much of a fossil record. Even in relatively recent times, humour is by its very nature likely to be erased from the official records. Many ancient writings are religious in nature, and therefore not inclined to have too many jokes in them.
We may never know which of our ancestors it was, living in the long ago world of the tribal hunter gatherer, that first started making jokes and laughing at them.
Note: an earlier version of this article was originally published at http://www.1729.com/column/9June2000-humour.html.