Sunday, November 05, 2006

Panspermia in Star Trek

Last week, Nick Matzke, public information project director for the National Center for Science Education, was interviewed on the SciPhi Show, a podcast about science and philosophy. The focus of the interview was evolution and intelligent design, but it touched on science fiction as well. According to Matzke's post on the Panda's Thumb:
In addition to pointing out all the usual ID mistakes, there was an interesting discussion about Star Trek: Remember that Star Trek episode where they discover that the suspiciously coincidental bipedal, humanlike form of all of the Star Trek aliens was (somehow) encoded into bacteria seeded across the galaxy billions of years ago, by an ancient bipedal race, a fact revealed when a 3-D holograph recording is deciphered out of the ancestral DNA genome (somehow!). The only thing the episode left out was an explanation for human-klingon-vulcan interfertility. Great episode, typically ludicrous science, but does it help the ID guys make their case?
The Star Trek: The Next Generation episode, "The Chase " reveals that, in the Star Trek universe, the galaxy's humanoid races have a common ancestor that was seeded on many planets by a technologically advanced race. As an ancient humanoid explains to Captain Picard:
You're wondering who we are; why we have done this; how it has come that I stand before you - the image of a being from so long ago. Life evolved on my planet before all others in this part of the galaxy. We left our world, explored the stars and found none like ourselves. Our civilization thrived for ages, but what is the life of one race, compared to the vast stretches of cosmic time?

We knew that one day we would be gone, and nothing of us would survive - so we left you. Our scientists seeded the primordial oceans of many worlds, where life was in its infancy. The seed codes directed your evolution toward a physical form resembling ours: this body you see before you, which is of course shaped as yours is shaped, for you are the end result. The seed codes also contain this message, which is scattered in fragments on many different worlds.

It was our hope that you would have to come together in fellowship and companionship to hear this message, and if you can see and hear me, our hope has been fulfilled. You are a monument, not to our greatness, but to our existence. That was our wish - that you too would know life and would keep alive our memory. There is something of us in each of you, and so, something of you in each other. Remember us.
This is a variant of the panspermia hypothesis, which proposes that "that the seeds of life are ubiquitous in the Universe, that they may have delivered life to Earth, and that they may deliver or have delivered life to other habitable bodies; also the process of such delivery". It shows up in a number of different science fiction stories.

Is it possible in real life? Not in the version presented in Star Trek*. Based on the ancient humanoid's description, the alien "seeds" co-opted the primitive organisms that were already evolving on many planets, and "directed" their evolution. The implication is that the "seed codes" took over the evolutionary process, allowing the life forms to bypass the forces of natural selection and develop into humanoids in the image of the "seeders". I would think that this would often result in species that were poorly adapted to their local environments and ultimately cause extinction of the proto-humanoid species on some planets. Of course for the special "code" hidden in the genomes of many worlds to be readable after millions of years that sequence must be essentially impervious to mutation.

Even if we assume that a "seed code" could direct evolution into humanoids, the basic genetic starting material of the original primitive life would have presumably been different on each planet. After millions of years of evolution, there should be remnants of that original genetic code in the genomes of modern species. The more likely alternative would be that the "seed" was the real progenitor of life in our galaxy, simply out-competing the indigenous primitive species. Even so, it's hard to imagine how the resulting humanoids, after millions of years of evolution, would be genetically similar enough to allow human-vulcan, human-klingon, and other interspecies hybrids. It's not even clear that humans can form hybrids with our closest cousins, the chimpanzees, so it's incredibly unlikely that humans could hybridize with species that have a different number of ribs, hearts, lungs and other organs.

What about more scientifically plausible versions of panspermia? At one time, no less a scientist than Francis Crick suggested that it was indeed possible:
It now seems unlikely that extraterrestrial living organisms could have reached the earth either as spores driven by the radiation pressure from another star or as living organisms embedded in a meteorite. As an alternative to these nineteenth-century mechanisms, we have considered Directed Panspermia, the theory that organisms were deliberately transmitted to the earth by intelligent beings on another planet. We conclude that it is possible that life reached the earth in this way, but that the scientific evidence is inadequate at the present time to say anything about the probability." (from Crick & Orgel, "Directed Panspermia", Icarus 19: 341-346 (1973) (pdf))**
It turns out that spores from other planets are actually a possibility. There is an interesting article in last November's Scientific American that describes recent research suggesting that microorganisms could indeed survive the trip from Mars to Earth. Of course, "possible" is not equivalent to "probable". The authors point to the issues needed to be resolved before science can even project whether that's a likely scenario or not.
Because it is not possible at this time to quantify all the steps of the panspermia scenario, investigators cannot estimate how much biological material or how many living cells most likely arrived at Earth's surface in a given period. Moreover, the transfer of viable organisms does not automatically imply the successful seeding of the planet that receives them, particularly if the planet already has life. If, for example, Martian microbes arrived on Earth after life independently arose on our planet, the extraterrestrial organisms may not have been able to replace or coexist with the homegrown species. It is also conceivable that Martian life did find a suitable niche on Earth but that scientists have simply not identified it yet. Researchers have inventoried no more than a few percent of the total number of bacterial species on this planet. Groups of organisms that are genetically unrelated to the known life on Earth might exist unrecognized right under our noses. (Warmflash & Weiss "Did Life Come from Another World?", Scientific American (2005)).
The question of whether life on earth (and other planets) originated elsewhere in the universe is still unanswered. Listen to the SciPhi interview to find out Nick Matzke's take.

NOTES:
* Star Trek often resorts to scientifically ridiculous versions of "evolution" as a plot device. For example, see Star Trek: The Next Generation "Genesis" ("Barclay's Protomorphosis Syndrome" causes activation of "dormant" genes and introns (!), resulting in "de-evolution" of the crew: humans Riker and Barclay turn into a Neanderthal and spider (!), respectively, Klingon Worf becomes a lizard-like humanoid, and Betazoid Troi turns amphibian-like) and Star Trek: Voyager "Threshold" ("Transwarp Evolutionary Syndrome" causes "hyperevolution" of humans into amphibian form). There is too much bad biology in these episodes to go into in this post.

** Orgel and Crick revisited the issue of the origin of life in 1993 and conceded that development of life on earth was more likely than they had originally concluded, based on research pointing to an initial "RNA World", rather than a "protein world" (Orgel & Crick "Anticipating an RNA world. Some past speculations on the origin of life: where are they today?", FASEB J. 7:238-9 (1993) (pdf)).

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5 comments:

Nano said...

great site but the 2nd paragraph from the parent humanoids' hologram in The Chase is not quite accurate ... it should read:

"Our scientists seeded the primordial oceans of many worlds
where life was in its infancy.
This body you see before you, which is of course shaped as yours is shaped, for you are the end result.
The seed code also contains this message, which was scattered in fragments on many different worlds."

Spacerguy said...

Genesis is a great Star Trek episode. Worf is so scary!

tramp394 said...

Star Trek is a great TV show. I am a big fan of 'Star Trek'. Overall, the show was truly a stepping stone into the new age of TV. It definitely will live long and prosper!!! You can also watch this show from here, so go ahead and Download Star Trek Episodes & enjoy your precious time with this!!!

Unknown said...

Humans and fish have different numbers of, and different arrangements of bones in their limbs, but both are controlled by very similar genes. The same should apply to pretty much all notochords.

Extrapolate that backwards to genes encoding quadruped symmetry (bilateral body plan, fore-and-aft gut) aggregates of ordinarily free-living bacteria when their population density gets high enough and interpolating the intermediate steps isn't completely unimaginable.

If you can swallow somebody being able to do all that, seeding the progenitor bacteria to be seeded on multiple likely planets isn't too much of a stretch.

We should go look. ;>)

Anonymous said...

You know, in a science fantasy where they can travel faster than light, why can't they create technology-indistinguishable-from-magic "seeds" to direct evolution within different ecosystems into a common goal-path phenotype?