What is it that we know of sentient biological life? We know that it fights to survive and propagate. We know that it changes and adapts as the surroundings necessitate. We know that it evolves.
Not being a biologist, I apologize for my simplicity. What I am getting at are the fundamental qualities in us that are likely to be similar in them. Earth biology follows certain rules. While extraterrestrial biology may be very different it is likely to be subject to many of the same rules.
What else might be similar?
How about civilization? We know that it developed to help human beings survive. We know that structures of society were created for a reason: the continuation of our species. Everything that comes with society is based on this foundation. We also know it can go horribly awry. War and genocide are actions of societies. You can have plenty of violence between individual human beings but it takes civilization to have a war.
We can be corrupt, self-serving, and downright awful to other human beings. We can feel love, compassion and make huge sacrifices for each other. We are all of this, mixed up, twisted together and changing from one impulse to the next, each and every day.
So, what about them?
You would have to assume that all biological beings are subject to weakness of some sort. Evolution has been at work for many tens of thousands of years and yet we are still able to bash each other’s heads in. It would be naïve to think it is any different for extraterrestrials. They would most likely be thousands of years ahead of us in the realm of technology, if they have the ability to visit planet Earth. They may have developed civilizations more advanced than we can even understand. They may have mastered many things beyond our comprehension. And yet there is still the biological imperative. They will be fallible. They will have weaknesses. They may not be the same weaknesses that we experience. They may not be violent at all. Corruption may not even be something they understand. But they will have weaknesses.
We must be very careful when heading into future relationships with extraterrestrial civilizations. We must figure out their motivations, their needs and ultimately their nature. They are here for a reason. What is the reason and what does that mean for us? It will be easy to place extraterrestrials on an altar and worship them as new gods. That would be dangerous and foolhardy.
Given that, do we brandish arms and keep them at a distance? Do we demand they leave and only return on our terms? That too would be naïve. We really have no choice but to say hello. We must smile and extend a hand. Then we must work to understand what they want and how that will impact us. We must move very slowly and carefully. We must evaluate every new piece of information and every new request. To a certain extent we must ask that they approach us on our terms. If they are hostile this might not happen. If they are friendly they will understand our concern and probably move at the speed we desire.
We have only a mirror to help us ponder what other beings might be like. We hold up that mirror and gaze at our own reflection. In it we can see the strengths and weaknesses of generation upon generation. One day we may have other models to understand. We may see ourselves in some continuum of sentient, civilized beings. Until then we have only one place to look and we best look very closely as we think about First Contact.