I have always wondered, and I don’t think I have asked it yet on these boards. What is the Straight Dope on the theory of Panspermia, that we have been seeded here from extraterrestrial sources? (The theory has two versions. In one, we have received proto-genetic material from other planets, like Mars, purely by accident. In the other, we have been deliberately seeded here by advanced ET’s. I choose the second one for my question, because it is more controversial–and more interesting, I think.)

I know there is the ancient astronaut theory, which I shall avoid. Just looking over the internet, it is clearly the domain of nut cases. But why not the second example of Panspermia? I know one thing that has always surprised me, is how far evolved humans are from other animals. There is no other animal on earth whose intelligence even comes close to that of humans–and that does include the lower primates, of course. Could that be no accident? Could our evolution have been given a helping hand, even?

I know Star Trek: TNG even did a story on it, here. Not the best cite, I know. But is shows some people in the mainstream have been at least thinking about it.

BTW, I ask for the “Straight Dope”. But also know this question will strike fierce debate. So I deliberately put it in Great Debates.

So how plausible, or at least mainstream, is the theory? And what do the rest of you think?

Please keep it civil (I am only asking the question, I am not submitting any opinion of my own, as of yet). And please keep at least an open mind, too.


I haven’t studied the theory, but for the moment I’ll go with ‘doubtful’.

The key to life evolving is plentiful chemical reactions in an environment rich with different molecules. Someplace like an ocean volcanic vent is pretty ideal. So given that we basically have the ideal breading reactor for life right here, it seems unlikely that it would have been seeded from elsewhere.

Only if you consider the present situation. We have, in the near past, shared this world with other intelligent primates, and before that, there’s a whole continuum of the evolution of intelligence in our lineage. It clearly didn’t arise ex nihilo.

The seeded-with-precursor-organics is the only version of Panspermia that has any credence based on actual evidence.

The Star Trek: the Next Generation episode is honestly the first thing I thought of too. I’m afraid that makes it a bit hard for me to take seriously, especially with the lack of positive evidence.

ETA: Yes, I realized that, which is why I’ve edited my post accordingly. I’m just sad that you saw it and replied to it while I was typing. :stuck_out_tongue:

“TNG” = “the Next Generation”:slight_smile:

The game Spore involves panspermia where life comes from a meteorite which breaks into pieces all over the world.

About Star Trek:

That would explain why the aliens are usually so human-like… or maybe they didn’t have the special effects in the early years to make really different aliens.

Just to be clear, the idea of panspermia doesn’t mean that someone came along and tweaked the evolution of humans. Panspermia means that the first replicating molecules or DNA or cells got seeded here from elsewhere.

I don’t know what the idea would be called if we were visited by special beings to tweak our evolution, but it’s a very different idea from panspermia.

We have only one example of a biosphere, which is planet Earth. And every organism we’ve ever found on Earth is closely related biochemically to every other organism. So there is only one strain of life on Earth today. It might have been in the past that there were several competing independently arisen strains of life, but very early in the evolution of life one strain subsumed all others, if any existed.

So to get a good answer to the question, we’d need to find an example of life on some other planet. If we find fossils or living life forms on Mars, we could determine if those organisms are biochemically related to Earth life forms. If they are, then it’s very likely that Panspermia is correct. Either life arose on Mars and spread to Earth, or life arose on Earth and spread to Mars, or life arose in another location and spread to both Mars and Earth.

On the other hand, if life on Mars is radically different biochemically, then it would seem likely that Panspermia is incorrect. If life can’t spread between two planets as close as Mars and Earth, where we have direct evidence of exchanged material (Martian meteorites), then how is life supposed to spread between solar systems? Of course, it could be that there are several lineages of life that spread through the Galaxy, and one form happened to colonize Mars and another colonized Earth.

But the point is, this is all speculation. We’ve never yet found any evidence of life outside of Earth’s biosphere, and until we do we can’t say very much about how likely Panspermia is. Or, if we explore and find lots of places that would be hospitable to life, but never find any examples of life, that would tend to disprove Panspermia. If life can’t spread to these hospitable places, then how could it have spread to Earth? If we can’t find an extraterrestrial source of life that could have seeded Earth, then where did life on Earth come from? It becomes more and more likely that life evolved independently on Earth.

As for the notion that human beings are “more evolved” than other creatures:

This is an important point that I think a lot of people miss. Imagine life having started as a dot, with evolutionary lines stretching out in equal lengths in all directions, creating a sort of ball. As time marches on, the surface of that ball gets bigger and bigger and the evolutionary lines that pierce the surface are what we see today. Some of those lines pierce the surface very close together, others further apart. But we’re only seeing the surface, not all the lines tracing back into the ball. (And most lines never even make it to the surface, having become extinct at some point.)

Just how close we are to our nearest “dot” cousin might be debatable, but there are continuous lines from those two dots, tracing back in time to the same point.

Before anyone gets too invested in the idea that we are “sooooo much more intelligent than any other animal”, you might want to read Franz de Waal’s new book: Are We Smart Enough to Know How Smart Animals Are?

There is also, what I guess you could call, another interesting aspect of panspermia, in my life at least.

Sometimes I pick on my fingers. It is a terrible habit. But sometimes they bleed. And just for the heck of it, I squeeze a couple of drops into my toilet, and then flush. And it fascinates me, what could ultimately become of my DNA, once let loose in the water and sewage system.

My DNA is uniquely my own. And now it will be carried miles, maybe even ultimately hundreds of miles, from my home.

Anyways, it also could bring up the idea of panspermia. What ultimately will become of my DNA, in the example above? Could it some day, maybe thousands of years from now, maybe sooner, end up on a meteor, ultimately crashing into another planet? I am not saying it will happen, or even that it is likely. But what exactly are the possibilities, here?

As I said, I thought I would just throw this item in, for the heck of it.

There is zero actual evidence for panspermia, and even if we assumed it to be true it just shifts the burden of abiogenesis and resulting evolution to another locale. As for the notion that human beings are some kind of special that is inexplicable by normal evolutionary pressures and processes, while there are no creatures as demonstrably intelligent as humans there are plenty of animals that are intelligent enough to arguably be self-aware. And while we tend to think pretty highly of our finger-counting and rhythm-making abilities, a truly intelligent race would arguably be better at not balkanizing their communication methods and fighting with each other in inherently self-destructive ways, plus they’d probably spend more effort trying to fight of parasites than on sporting pastimes, and would invest more in understanding the nature of the world than the exploitation of its limited resources for short-term profit.

We are not all that smart. Even the very best of us.


This my take on the matter … if life can arise someplace, then it can arise on Earth … it’s the economical solution.

Also, if life here was seeded from beyond, then we’d still be being seeded, we should be able to find these seeds on places like the moon or asteroids.

Excellent comment, John (and also, MrDibble). And thanks for the book suggestion, I’m definitely adding it to my reading list. It’s long been my casual impression that we as a species are extraordinarily arrogant about dismissing non-human forms of intelligence, and amazingly narrow-minded in our lack of ability to recognize it. In fact I think this exact syndrome is now playing out in dismissive attitudes not just to animal intelligence but to machine intelligence, which tends to have vastly different manifestations but we humans are versatile – we can dismiss all of it!

We have a shared evolutionary history with animals practically as old as the earth itself. The cultural anthropologist Clifford Geertz beautifully expressed our pompous rejection of this common ancestry when he said “Man is an animal suspended in webs of significance he himself has spun.”