Simply because for the next few hundred years, they will have to have come to us, which immediately places them in the position of power. Yet, (if) we become highly mobile in space and find other life, we could easily be the ones in power.

It’s almost impossible that we will be contacted by little green men, stepping out of their flying saucers in front of the white house. Instead, if the SETI search continues at its current pace, it is possible that some time in the next few decades we will have our first evidence of an extra-terrestrial intelligence. This could be either in the form of received radio signals, or an exo-planet, who's atmosphere shows telltale markers of an industrial civilization.

What happens next is as much a political question as a scientific one. Even if we sit on the news for years, its obvious that someone is eventually going to try and send a signal back. The UN has a role to play in ensuring that first contact is handled in a calm and thought out way. Unless there is somebody in a position to co-ordinate things, every other country with a radio telescope will be beaming up signals. Would you really want first contact to come from the US, China, North Korea, Russia and France, all at the same time? It’s good that the UN is thinking about these problems now, so that if, and when that momentous day does arrive, we are prepared to speak clearly, with one unified voice.

I'm curious what the probability is that this statement is true. Alien species that have been around much longer than us may view humans as microbe-like in intelligence.

Essentially: chimpanzees share ~98% of our DNA, yet we don't view them as having anything near our intelligence. If it only takes a 2% difference for this to happen, imagine how more advanced alien species might view us.

It's not the least bit surprising for 2% to make such a large difference. We deal with this sort of thing on a highly regular basis -- ordering food at a restaurant, writing code, reading books, having conversations...

The 2% example says the obvious: "Aliens could be really advanced compared to humans because they're different from humans in a way that makes them really advanced."

Even an alien civilization that may seem like gods to us won't confuse us with our genomic neighbors.

It is similarly imaginable that evolution could, without breaking a sweat, spit out intelligence that would consider us stupid the same way we consider chimpanzees stupid. They can do some cute tricks but that’s about it.

He basically wants to open our eyes to the idea of a vast scale of intelligence, not between village idiot and Einstein but spanning much wider. Meeting someone that is just as intelligent as we are seems unlikely.

A book called "Power, Sex, Suicide: Mitochondria and the Meaning of Life" provides some insights. The author argues that the only reason multicellular organisms evolved is that one type of cells ("host") engulfed (or engaged into symbiotic relationship with) another, that became mitochondria and was used as a "power plant". This probably happened only once in history and under very specific conditions, which are very unlikely to be repeated.

  > This probably happened only once in history and under
  > very specific conditions, which are very unlikely to be
  > repeated.

Without having more data points, it is hard to say whether the average life span of a planet in the Universe is long enough for multicellular life to inevitably develop.

So far, all evidence points to no. It is also true, however, that so far we have negligible data.

If an alien civilization was to find and visit us (by means other than microbes riding an asteroid...) then their technology is at least a few hundred years ahead of ours.

You would most likely meet completely unintelligent microbes on Earth. Or no life at all. Maybe some stupid animals or plants.

The likelihood of meeting intelligent life during the existence of this planet is something like 0.004 percent (200,000 years of intelligent life on a 4.5 billion year old planet), the likelihood of meeting nothing but microbes is greater than fifty percent. It’s consequently only reasonable to expect most alien life to be microbes.

Older intelligent civilizations could certainly exist on older planets but the age of the universe is only 14 billion years. If the average planet is something like 7 billion years old (based on the naive assumption that planets form at a constant rate) then it is only reasonable to expect that most intelligent life out there existed for no longer than something like 2.5 billion years. Oh, and past mass extinctions on Earth cast serious doubt on the ability of complex life to survive for very long. Microbes, on the other hand, are undisturbed by asteroids and volcanoes.

That’s not human arrogance. That’s just how it looks to be at the moment.

Should we find an Earth-like planet sometime in the future and detect oxygen in its atmosphere I would expect to meet microbes, not intelligent beings. (We will certainly be able to detect Earth-like planets very soon and we might even be able to detect whether those planets have oxygen but we will probably never be able to actually go there so this point is kind of moot.)

Human arrogance I say (and that is not aimed at you personally).

We're making assumptions based on a ridiculously small and sparse amount of knowledge. We assume the universe is 14 billion years old, we assume other lifeforms are carbon based like us and evolve the same way we do, we assume faster-than-light travel is not possible.

I don't see how this is any different to how we assumed the earth is flat, just a few hundred years ago.

In the grand scheme of things we simply don't know enough to make anything but the wildest guesses about alien intelligent life. Considering ourselves to be the pinnacle of evolution at this point seems very naive.

Our dataset about life is ostensibly limited to earth-based life. If we abandon available data, we are limited to making wild untestable conjectures.

What is the alternative? Should we just stop thinking about it?

It’s a wild guess (astrophysicists would take exception, however, with the assertion that they got the age of the universe wrong) but it’s also the best we have. And there is nothing wrong with that and it is not arrogance.

Err, I had no idea that flowers appeared later than mammals and birds. Is that a well-known fact that I should've learned in high school?

For instance, in Heinlein's "Stranger in a Strange Land" the Martians ponder destroying the Earth "for aesthetic reasons".

we are the aliens.