Science Magazine is celebrating its 125th anniversary with 125 big questions that scientists will face in the next 25 years. You can read them all for free here. For the 25 biggest questions, the editors commissioned short essays. I addressed the minor matter of how and where life began.
Fortunately, I get to ask the question. I don't have to provide the final answer. A science writer's prerogative.
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Carl Zimmer wrote:
"If life does turn up,(on Mars) the discovery could mean that life arose independently on both planets--suggesting that it is common in the universe--or that it arose on one planet and spread to the other."
You overlooked the really interesting question. If life is found on Mars (or elsewhere), is the genetic code the same? The chances of the same genetic code arising independently at two separate locations is astronomically unlikely, so it would support the second scenario.
However, the chances are even better that life is endemic throughout the universe and spread to earth and Mars from elsewhere. This begs the question: "how did this life emerge elsewhere, it must have evolved somewhere?"
But we must also consider the possibility that life and the universe have always existed and that asking the question "where did life come from"? may be no different from asking the question "where did matter come from"?
Besides, evolutionary biologists do not feel that they have to explain the origin of life (abiogenesis) to promote their theory of evolution so it seems fair that folks like me, who advocate for Cosmic Ancestry (panspermia) shouldn't have to explain where the extraterrestrial life originally came from.
All of the available evidence supports the notion that life did come to earth from elsewhere with all of the information present that was necessary for it to evolve into it's present form.
And by "elsewhere" I don't necessarily mean "above". There is growing evidence that at least some life forms may have had their origin inside the earth.
"Besides, evolutionary biologists do not feel that they have to explain the origin of life..."
Biology describes life (of course), not the prehistory. But evolution is applicable in the transition from chemistry soup to cellular life.
"... so it seems fair that folks like me, who advocate for Cosmic Ancestry (panspermia) shouldn't have to explain where the extraterrestrial life originally came from... "
Not to prove panspermia. But panspermia is not proved.
"... life did come to earth from elsewhere with all of the information present that was necessary for it to evolve into it's present form."
But this is not panspermia but creationism, a belief system which has no explanatory value. How does your belief system account for where the information come from?
Also, panspermia is based on the robustness of simple cell spores. How does your belief system account for that complicated cells with 'the necessary information' survived cosmic radiation for a very long period?
Charlie W comments:
Although you're right in that, to hypothesise that life came from elsewhere it's not necessary to identify precisely from where it came, you would need to at least show evidence that it did indeed originate "elsewhere" for the hypothesis to gain any validity. A "preponderance of evidence" is only possible with the existence of any actual evidence, for starters.
Re: characterization of evolutionary biologists. Charlie and his ilk apparently think its clever to insinuate that biologists need to "promote" the theory of evolution. This, as opposed to studying and testing the model's various components, which they constantly do, and allowing it to evolve, which it constantly does. The theory of evolution is not a political initiative or a marketing game; it's an amazingly robust and ever-maturing model of biological life, which does not need to be "promoted" a la popularity contests.
More CW:
I'm not saying you're absolutely wrong about Panspermia - although I personally am not in agreement - but "All of the available evidence"?!
What are you smoking, CW? You didn't really mean to use that phrase, right? :-)
What I find most interesting about your comment though, CW, is the suggestion that all biological evolution on earth has rolled out pre-loaded like a genetic time-release program of some sort. That's a doozy. Is the theory that the roll-out is now complete and that of the billions of years of mutation or switch-flipping or whatever, this is an intended end result (fantasticly, just as we humans have finally mapped the human genome)? Or, fast forward 2 million years from now, life as it exists on earth at that point, is that part of the program too? Is that the intended end result? Is there a point of "/evolution" in your scenario?
Don S wrote:
"What are you smoking, CW? "
Acapulco Gold, when I can get it ;-)
"you would need to at least show evidence that it did indeed originate "elsewhere" for the hypothesis to gain any validity."
There is evidence. A lot of it.
Most of it is circumstantial, but you can make a very strong case. The rapid appearance of major classes with no apparent precursors is the main clue. The 1.4 billion year period during which there was no evolution beyond unicellular forms, followed by the rapid appearance of most of the major animal phyla in a very short period of time is suggestive.
One major prediction of cosmic sncestry is that genes should be older than the organisms that use them, whereas evolutionary theory requires them to be expressed immediately so that selection can operate. This prediction has been shown to be supported by empirical data such as Carl discussed in jellyfish. Recent molecular analysis of several metazoan genes has confirmed that they appear to have "diverged" from their respective common ancestor genes much longer ago than the Cambrian explosion. Many genes, including those that operate at the most fundamental level are being shown to have preceeded the organisms that use them.
In January 2006, the "Stardust" spacecraft will return to earth with material it sampled from comet Wild-2. This may give us new insights into the possible transport of living/organic matter around the extraterrestrial environment by comets.
Certainly, cosmic ancestry is not a proven mechanism, but it is scientific and it is testable. In fact, NASA has devoted substantial resourses to it's investigation. As Feynman says, science is not about proving things, but deciding what is most likely. Right now, I think any informed person would easily come to the conclusion that it is much more likely that life came to earth from elsewhere than that it arose de novo on a barren, primordal earth.
Like the mayfly larvae that lives at the bottom of the pond and cannot know nor does it have the capacity to understand the world above the pond, so we humans may be existing in a universe that we cannot know and possibly do not have the capacity to understand, and there may well be intelligences in the universe as far above us as we are above the bacterium.
Charlie:
So, it's "far more likely" that life arose and developed originally on a different barren planet and evolved and then it travelled across the vast reaches of space and somehow survived the trip and then dropped onto the earth where it perfectly adapted to the environment here and fabulously fit in with the pre-existing unicellular life here, then evolved to the point we're at right now.
I don't say that's impossible but, you say "any informed person would easily" come to that conclusion? If ever there is an opportunity to properly apply Occam's Razor, then this is it!
I'm a layman, but nevertheless the above appears absurd. Am I mischaracterizing the process you propose somehow?
But it also looks like you're leaning on the - and again, I'm a layman - debunked assumption that there was no real complexity until the Cambrian. Am I wrong about that too?
But finally, by what you say above it seems that you accept that at least unicellular life developed here on earth, on its own, right? Well, but isn't that the big hurdle?
If you don't have any objection to the facts that abiogenesis occured here on the barren primordial earth, and a billion years of unicellular life shows that, then where's the problem? The only problem you're left with is the Cambrian Explosion, which really is far less of a "problem" than abiogenesis, right?
If two main scenarios here are that either that unicellular life evolved over some 900 million years to our current complexity, vs. the superspores from another orb travelling across millions or billions of light years and impossibly dropping in at just the right time, why so much effort to infer from the "circumstantial" evidence that that idea is the right one? Rather, the reason I'm replying here, how is it a "far more likely" scenario?
I don't get the reasoning, forgive me.
The answers to all 125 problems are quite trivial. You'll see after they're solved.
Don S wrote:
"If ever there is an opportunity to properly apply Occam's Razor, then this is it!"
I agree. All of our experience supports the view that all life comes from pre-existing life. So it's much more reasonable to think that the life forms on this earth came from pre-existing life forms than to think (absent any reasonable explanation) that they arose from nothing on a lifeless and barren primordal earth.
If an explorer in the 19th century came upon a remote island inhabited by large numbers of living organisms would he make the assumption that these life forms bootstrapped themselves into existence from the raw materials on the island, or would he assume that they had migrated from elsewhere? We don't have to know where they came from or even how they came to be to make this assumption.
Life came from space because life comes from life.
"it also looks like you're leaning on the - and again, I'm a layman - debunked assumption that there was no real complexity until the Cambrian. Am I wrong about that too?"
Complexity is not the issue. The issue is organization. unicellular life existed for billions of years with no evolution to metazoan forms. In the Cambrian, metazoan forms emerged rapidly in numerous phyla all over the world in a very short period of time. No darwinian mechanism can explain this rapid and widespread advancement.
"by what you say above it seems that you accept that at least unicellular life developed here on earth, on its own, right?"
Don't know, but my guess is no. All life on earth (IMHO) came from pre-existing life it did not arise from nothing.
Since life is the absence of death, life on earth arose when some process (or god) eliminated some death, thereby providing a niche for life.
Nobody cares what you think Charlie.
For those wondering about CWs view point let me give you some details from months of reading his posts.
Charlie believes the Universe, against the available evidence, is infinitely old. I'll expand on this since there are some cosmological models that say the universe may technically infinite. Charlie Wagners infinite universe is infinite in that its always been like we see it now...conducive to not only atomic structure but complex life.
Charlie believes that a complex alien life has existed for this entire time and that it is responsible for seeding life everywhere in the universe.
Charlie believes that no life can become more complex. The super aliens are the top of ladder when it comes to complexity and even they can not create something more complex then themselves.
Charlie believes these aliens are not supernatural nor do they possess the ability to exist outside our known universe.
Charlie does not believe, contrary to all current evidence, that the universe had any type of big bang.
So Charlie's hypotheses breaks down at the first point that the universe is infinitely old.
Charlie's on the pandas thumb he equated this super alien to the Q from Star Trek.
Note also if you've visited his web site you'll know that he also doesn't believe cholesterol (spelling) doesn't contribute to heart disease and other.let us say novel ideas.
I might pay some of his ideas a bit more thought if they didnt run up against fundamental facts we know about the universe and its origin. Charlies understanding of cosmology is very lacking.
"Don't know, but my guess is no. All life on earth (IMHO) came from pre-existing life it did not arise from nothing. "
I hate when people say that life could not come from 'nothing'.....it didn't....organic compounds came from simpler molecules.
Just like molecules came from atoms atoms came from sub atomic particles(P/N/E) they came from even smaller components. Currently strings are just one theory on what the smallest structure might be....but as history shows us the closer we look the more we see....so maybe if strings turn out to be true then strings may have some components they are comprised of.
The first time I read a CW thread he came over as a regular IDiot crackpot.
This time he introduced panspermia seemingly out of the black ;-), so I pegged him as borderline; they tend to change topic at their indiscretion and expand agendas infinitely.
But from the CV on CW it seems he _is_ crackpot, just an infinite one. :-)
Panda's thumb - thanks for the tip. Also the quick course in sesamoid bones I had to take to handle the handle! (The aha experience from things like this may be close to what people feel when they have religion hardwired into their brain.)
"then strings may have some components" - branes. Apparently strings are branes in an embedding M theory.
But we must be careful here - the russian doll syndrome invites to another infinite confusion for people like CW.
I think string/M theory may level the Plank limit to the ground but it claims to maybe be the selfconsistent Final Theory ("TOE") road block instead.
Anyhow, I don't think physicists believe in the russian doll scenario anyway for very good reasons. (Probably lots of unreal infinites cropping up.)
Come to think of it, isn't it funny that people believes that infinities are real?
Obviously they are not - to measure one you need either infinite short time/high energy (russian doll) or infinite long time/low energy.
In real life (that we can measure or experience or live in) quantum & Plank limits takes care of the energy perspective. And Big Bang and entropy death frames the time perspective. (And even if we had an infinite clock to measure infinite time or length, who would care to wait for the result? :)
So infinities are idealisations that are convenient but untrue. Like gods for 'explaining'. But since they are convenient and untrue I guess they are 'evil'. Hey, a proof that gods are evil! :)