[Astro9k]

"they are more likely to be microbes than anything intelligent"

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.

[kyleslattery]

Astrophysicist Neil Tyson makes a great point on this: http://www.youtube.com/watch?v=w-uZZ7RdL5E

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.

[manicbovine]

I really dislike this example because the underlying metric is so poor.

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."

[mortenjorck]

We may have a genome that is only two percent different from that of a primate, but the result is nothing short of a singularity. Chimpanzees may be amazingly advanced mammals, with complex social systems and the ability to use sticks as limited tools, but... Our two percentage points gave us Shakespeare, the Italian Renaissance, jazz, the wheel, skyscrapers, the Apollo Program, agriculture, global telecommunications networks, gunpowder, the Cold War...

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

[endtime]

What does DNA have to do with it?

[ugh]

The point is that our next relatives on the tree of life are very similar to us in many ways but we would nevertheless consider them pretty stupid. Pretty much all impressive human achievements will be forever inaccessible to them. DNA is just a very striking way of illustrating that similarity with the one big difference.

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.

[endtime]

I understood what he meant, I just didn't understand why DNA was helpful in illustrating it. I'm a lot smarter than a nematode, or a pebble, or a cell in Conway's Game of Life. The number of base pairs I share with any of those things (where applicable) is irrelevant.

[carbocation]

That's a 60MB difference in a 3GB text file. The message could be wildly different...

[Evgeny]

A point to consider is the probability that microbes ever evolve into something more complex (multicellular organisms). After all, there are huge amounts of bacteria on Earth these days, but I'm not aware of any cases of them evolving into more complex organisms in the last billion year or so.

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.

[joeyo]

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

Anything not forbidden is compulsory. -- Murray Gell-Mann

[ajju]

"Anything not forbidden is compulsory" only if you assume an infinitely long time horizon

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.

[carbocation]

Wolbachia has a remarkable relationship, with some species dependent upon it for fertility. I'd say that endosymbiosis has occurred independently a few times.

[moe]

Indeed. Human arrogance I would say.

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.

[ugh]

Wikipedia has a helpful timeline of life on Earth: http://en.wikipedia.org/wiki/Timeline_of_evolution#Basic_tim...

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.)

[moe]

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

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.

[manicbovine]

It's much different from assuming a flat earth. There has always been good and readily available data supporting the hypothesis of a non-flat earth. Various cultures have used this data to realize that the earth is not flat.

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?

[ugh]

Nobody assumes that humans are any kind of pinnacle of evolution. I never said that, the submission never said that. There is a difference between “most life out there is probably microbes” and “all life except for life on Earth is microbes”.

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.

[nandemo]

> Wikipedia has a helpful timeline of life on Earth:

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?

[ugh]

Flowers are complicated, their late arrival is not really surprising. 130 million years is also not exactly recent. It’s not like some cavemen lived in a world without flowers.

[nandemo]

Another possibility is that -- regardless of their technological level -- they'll have completely different values and won't be interested in earthlings at all.

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

[patrickgzill]

"Thinking meat. Dreaming meat."