I've often thought it interesting that when SETI scientists imagine extraterrestrial civilizations, they usually think in terms of unified worlds that have one civilization. The image is very much unlike our world, in which we have multiple civilizations that are fractured and in conflict with other societies. The Brexit event of the past couple of days is a good example of just how fractured our world is as well as representing some solid data not in support of the idea that humans are becoming increasingly unified.
When we imagine other worlds, we tend to take a distant view and create images that reflect a fictionalized, romanticized representation of life right here on Earth. Rather than fractured worlds with many civilizations like the one on which we actually live, many SETI scientists think in terms of what I call the Star Trek Imaginary, in which each world forms a civilization equivalent to a geopolitical unit on Earth. In other words, we think of alien worlds as unified political states or countries.
There is a good chance that this is an inaccurate view of civilizations on other planets, but it still may be a useful way to think about extraterrestrial intelligence if only to deconstruct our assumptions about life on other worlds. Indeed, one way to use this image is to turn it around and think about Earth from the perspective of an alien world. This makes for an interesting thought experiment.
Suppose ET planted some sort of observational device near Earth, say, 6,000 years ago. Somehow, they had noticed that there seemed to be an emerging civilization and thought it would be interesting to study how things evolved. ET doesn't have a lot of time to spend on watching Earth and the observational device isn't sensitive enough to show all the nuances of political machinations throughout human history. So the data are limited in detail. The result is a wide-angle picture of Earth throughout history that gives a general sense of what cultural evolution on Earth is like. ET will have learned quite a bit, actually, about how humans evolve and form societies over time, but a lot of the detail will be left out. They probably won't get the nitty-gritties about the Brexit.
So what would such a device tell ET? As I thought about this, I realized there would be one overwhelming image ET would get about Earth. And it's an image we here--with our close-up picture of our own history--don't usually associate with civilization on this planet.
I think what ET might conclude is that Earth has been at war for about 5,000 years--pretty much non-stop. The first war in recorded history seems to have been in Mesopotamia around 2,700 BCE between Sumer and Elam, and from the outside it might look like it never stopped. Since that time, if one were to stand back a bit from Earth, there is a pretty good chance that warfare would be the dominant feature of human civilization. There is always war going on somewhere on Earth. It ebbs and flows in intensity. Sometimes it's regional; sometimes it covers most of the planet. But it is always there and it might look like one long war from an outside perch. If you didn't know all of the political and historical details, there would be no reason to assume that our history had been an endless string of wars rather than simply one really long one.
From our perspective, this would not be a very accurate picture. Different societies have had on-and-off periods of war and peace. And we don't tend to think about our civilization(s) as being characterized by a single war lasting 5,000 years, because we understand the geopolitical details in which there have been lots of wars over that time, not just one war. But if you look at Earth from the outside and treat human societies as a civilization, then it's probably a reasonable conclusion about us. From the external--or in anthropology what we would call etic--perspective, human civilization might appear to be based on and characterized by a single war that has spanned almost 5,000 years.
This raises the importance of seeing the difference between proximate and distant perspectives and the difficulties in imagining intelligent life and civilizations on other worlds when we don't have a lot of data to work with (or in our current situation, without any data at all). SETI scientists often tend to impose their own assumptions about intelligence and civilization on imagined extraterrestrial worlds and those assumptions are shaped by ideas about the way our world is that: 1) may not be empirically accurate, and 2) are unlikely to reflect how we would look to outsiders.
The devil is in the details, and we don't have any of those, since we have no evidence of alien intelligence. But even if we do get evidence sometime, we probably won't have much detail and we will need to be very careful to avoid imposing the Star Trek Imaginary--or any other set of assumptions--on what little data we receive. Standing back and trying to imagine what our world would look like to distant outsiders is a useful way of trying to control this tendency to imagine alien others in terms of romanticized images of ourselves.
Perspective is important. It may well be that characterizing our world as being at war for 5,000 years is accurate, but it isn't how we see ourselves and that, too, is an important piece of data about humans. Recognizing the potential disjuncture between how we see ourselves and how others might see us is a key component of trying to deflect, to the extent possible, our tendencies to infuse assumptions about intelligence and civilization drawn from our proximate understanding of and imagination about life on Earth into our speculations about intelligent life on other worlds.