Troubles in Paradise

March 4, 2015 8:06 AM

Troubles in Paradise is a review of the history and arguments of the creationism/intelligent design movement, written by James Downard.
posted by brundlefly (25 comments total)

There was an odd one in a collection of Curt Schilling's tweets DirtyOldTown linked to, in which he apparently thinks evolution would require that "every living organism on this planet came from 1 cell".
posted by XMLicious at 8:21 AM on March 4, 2015 [1 favorite]

He must be confusing evolution with the Biblical account.
posted by FatherDagon at 8:33 AM on March 4, 2015 [2 favorites]

Evekaryote was created from Adamchea's ribosome!
posted by XMLicious at 8:58 AM on March 4, 2015 [6 favorites]

he apparently thinks evolution would require that "every living organism on this planet came from 1 cell

Is there evidence to suggest that whatever pushed some type matter over the line from inert mass to what we would consider a distinct, self-replicating, living organism happened independently more than once in different parts of the world? In other words are there multiple, totally unrelated family trees of organisms on the Earth, or do they all fit together into one hugely diverse family tree? If the latter, isn't he more or less right? (Beyond his idea that a cell was the beginning as opposed to a remarkably sophisticated organism somewhere in the middle of the story, one that had already benefited from millions of years of evolution.)

(Because this appears to be necessary, allow me to specify that this is a totally serious question, devoid of sarcasm, and that I totally accept the idea of evolution and do not believe in a guiding, intelligent designer.)

(I'm serious about that too.)

(If need be, I can provide expressions of my earnestness all the way down, but at some point it might be best for all of us if we just accept that someone means what they say and is not attempting to sarcastically express its exact opposite.)
posted by Naberius at 9:02 AM on March 4, 2015 [1 favorite]

Well, the right-handedness of sugar (dextrose not levelose) and related chiral molecules in all known life's processes suggests we all have a common root. Whether that was one single "cell", or a group of functionally identical cells arising under near-identical circumstances, is not knowable.
posted by IAmBroom at 9:14 AM on March 4, 2015 [4 favorites]

Whether that was one single "cell", or a group of functionally identical cells arising under near-identical circumstances, is not knowable.

Therein lies the issue. Creationists see their position as absolutely knowable, because it's written in the Bible. Science admits to limits on what can be known, so how can it be correct?
posted by tommasz at 9:17 AM on March 4, 2015

"Suggests", not "requires".
posted by IAmBroom at 9:17 AM on March 4, 2015 [2 favorites]

Naberius, I had the same thought, so I can see where you're coming from. Furthermore, the answer to that question has somewhat universal implications. If life can arise more-or-less independently here on Earth, then that would seem to make it extremely likely to have arisen on other planets (now that we know planets are pretty common). On the other hand, if life arose only once on this planet, then it may not be nearly as common throughout the rest of the universe. I wonder if it is possible to determine whether life like that found near deep-sea vents arose independently of other primitive organisms, like those that formed stromatolites.
posted by TedW at 9:22 AM on March 4, 2015

There's also a world of possibilities between a choke point at one single cell versus life or life-precursors arising independently at multiple points around the globe, if indeed that is something that even happened on Earth at all.

If, say, the first cells were the result of some self-replicating molecule or structure combining with lipid bilayer bubbles (I'm not versed in the science concerning this, that's just a scenario I heard suggested in a documentary a long time ago) some phenomenon or environment could cause that to happen repeatedly, so that there wasn't a single initial cell.

The more I think about it, the more I have vague memories of creationist arguments that try to pick whatever they believe represents the simplest extant organism, then claim that for abiogenesis to be true that entire organism would have to spontaneously assemble all at once. Maybe this is seen as some sort of corollary to that.
posted by XMLicious at 9:44 AM on March 4, 2015

As another tack on the notion of life arising in multiple independent events here on Earth, the (entirely hypothetical so far, unfortunately) concept of the shadow biosphere may be of interest.
posted by XMLicious at 10:00 AM on March 4, 2015 [2 favorites]

IIRC, the number of random chemical reactions required to spontaneously generate self-replicating molecules is so large, compared to the number of molecules in the primordial oceans that (life having arisen here so quickly after the earth cooled) the likelihood is about 50/50 that life landed here from outer space. (Search term: panspermia).
posted by sexyrobot at 10:19 AM on March 4, 2015

(Search term: panspermia).

Which is basically just begging the question. We don't know how life could have evolved here, so we'll say it evolved elsewhere...where we don't know how it could have evolved."
posted by happyroach at 1:00 PM on March 4, 2015 [1 favorite]

What we can easily see is that life is extremely unlikely to arise by accident. Fortunately the universe, while probably not infinite, is fucking huge FUCKING HUGE enough to allow such an unlikely accident.
posted by fredludd at 1:07 PM on March 4, 2015 [2 favorites]

There was an odd one in a collection of Curt Schilling's tweets DirtyOldTown linked to, in which he apparently thinks evolution would require that "every living organism on this planet came from 1 cell".

That's the most commonly accepted model, yeah. The single-cell organism that was the progenitor of all life on earth is called LUCA: the last universal common ancestor. I guess I agree with Curt on this?

There's also a world of possibilities between a choke point at one single cell versus life or life-precursors arising independently at multiple points around the globe, if indeed that is something that even happened on Earth at all.

All evidence points to a single choke point. See the references to that Wikipedia article I linked to above, especially the Theobald Nature paper from 2010.
posted by mr_roboto at 1:38 PM on March 4, 2015

I take it you aren't saying that you agree with Schilling that what you point to there is so implausible that his Young Earth version of history is clearly the truth...

The abstract of the the Theobald Nature paper from 2010 says,

As first suggested by Darwin, the theory of UCA posits that all extant terrestrial organisms share a common genetic heritage, each being the genealogical descendant of a single species from the distant past.

[emphasis mine] I don't have access to the full text, so does he reach a conclusion that contradicts this by saying it needs to be an individual organism rather than a species?

I've read that Wikipedia article before, I just didn't get the impression it mandated a single cell as the common ancestor. For example it explicitly says at one point,

In 1998, Carl Woese proposed (1) that no individual organism can be considered a LUA, and (2) that the genetic heritage of all modern organisms derived through horizontal gene transfer among an ancient community of organisms.

posted by XMLicious at 2:09 PM on March 4, 2015

No; I don't agree with Shilling's views on evolution.

The argument regarding evolution from a single species vs. evolution from a single cell is moot. LUCA was a single-celled organism; the first individual representing this organism was therefore a single cell. All other individuals of this species were descendants of this single cell (as are we all).

Read the next few sentences after that description of the Woese proposal. This is no longer a widely held view. While life did evolve from a community of primordial organisms and there was certainly horizontal transfer of genes (or of something that acted like genetic information) within this community, LUCA represents an evolutionary bottleneck. A single species (originating from a single cell) from which all live evolved.
posted by mr_roboto at 2:28 PM on March 4, 2015

I love how design arguments leap from incredulity about abiogenesis and/or evolution (not the same thing) to total credulity about a designer. It's like, a cell could never just arise through some series of events, but something with the ability and intelligence to design cells ... just plain exists.

I can't see how we'll ever have anything but plausible hypothetical models of abiogenesis - it's not like we could identify how a fossilized single celled organism got its start even if we found the common ancestor of all life tomorrow. But with evolution we have a really robust, growing theory, and a tremendous body of fact.
posted by graymouser at 2:45 PM on March 4, 2015 [6 favorites]

LUCA was a single-celled organism; the first individual representing this organism was therefore a single cell. All other individuals of this species were descendants of this single cell (as are we all).

The sentences following what I quoted above still seem to contradict what you're saying here:

While the results described by the later papers Theobald (2010) and Saey (2010) demonstrate the existence of a single LUCA, the argument in Woese (1998) can still be applied to Ur-organisms. At the beginnings of life, ancestry was not as linear as it is today because the genetic code took time to evolve. Before high fidelity replication, organisms could not be easily mapped on a phylogenetic tree.

Linear descent from a single individual cell or not, though, I agree it's moot.

You're acting as though you're contradicting some claim I made about science. But what I meant by my "world of possibilities" comment there is similar to what graymouser is saying: even if someone finds utterly inconcievable the concept of a single-organism choke point (which is how I was reading Schilling's tweet, but maybe it's just twitter-enforced brevity) or finds a single-species choke point similarly unbelievable, it's not like the only two options are either that or Young Earth Creationism. (Or even that versus repeated instances of abiogenesis, I guess, given the idea I was replying to.)

This has been my experience in the past when speaking to at least some Creationists: that focus on trying to play whack-a-mole with some specific formulation of abiogenesis or evolution often betrays the fact that they aren't actually trying to examine the truth behind any particular topic; they act as though refuting any particular detail, even if their reasoning were sound, could be followed by "... ergo Creationism. Q.E.D."
posted by XMLicious at 3:23 PM on March 4, 2015 [1 favorite]

Trying to find Homer by proving the Earth orbits the sun. I wish I could be charmed by Creationist, um, creativity, but it seems to be too filled with neeners to warm me up. As mentioned in this thread, the advent of life remains speculative--we have some difficulty defining it, but we believe we know it when we see it. I'm not too sure of that last part. We can't define life on a cosmic scale in any meaningful way. For example, can it be proved that the stars being produced in the Eagle's Nest aren't the product of a self-aware entity? Some things are simply out of our reach, at least for the time being. Maybe our descendants will come upon keys to this sort of understanding in some way, say, the way we've discovered or invented (and employed) such things as radio frequencies and X-rays.

My version of the cosmos admits to the possibility that some macro-force created "our" universe in an act of will, for whatever purposes struck its fancy. Maybe our creator's makeup required it to create us and all we perceive, the way an amoeba must divide when certain conditions are met. None of my crackpot theorizing excludes our science. It just means that God might the next turtle down. That's not any harder for me to accept than the notion of life, a unique phenomenon, bubbling up out a chemical stew that came from stuff whipped out by a cosmic string or the residual ashes from the Big Bang. I do love the image of us, children born of stardust.

I have a harder time understanding the mind of the Creationist than any of the above. But still, thinking about them makes me feel so evolved.
posted by mule98J at 12:44 PM on March 5, 2015

I continued reading some more about LUCA and though I didn't find the full text of the original Theobald paper I found this paper from the subsequent year in full text on PubMed, in which he's responding to critics of the first paper. It's quite interesting and actually gets kind of funny when he starts bringing up Creationism in the course of discussing logical fallacies pertinent to the interpretation of statistics.

In the section where he's responding to reviewers he (Douglas Theobald) quotes his original paper:

UCA does not demand that the last universal common ancestor was a single organism, in accord with the traditional evolutionary view that common ancestors of species are groups, not individuals. Rather, the last universal common ancestor may have comprised a population of organisms with different genotypes that lived in different places at different times.

The fact of the matter is that organisms existed in the past that contained ancestral copies of these fundamental proteins, and that all known extant life has inherited descendant versions of these proteins from these ancestral organisms (at least that is the scenario that my model selection tests strongly support). Whether you want to call that ancestral group of organisms "a species", "a population", "an ancestor", "the LUCA", or something else is primarily an issue of semantics. My universal common ancestry models are also consistent with a single individual organism/cell that contained all the ancestral versions of these proteins, though that is extremely unlikely given basic pop-gen considerations (and even less likely with LGT).

Because all extant living organisms carry descendants of these fundamental proteins, at some point the ancestral group of organisms necessarily had the ability to exchange fundamental genetic material. This is one argument for calling this ancestral population a "species", regardless of whether it was exchanging genetic information via sex or LGT or whatever — e.g., that would be a strict application of the Biological Species Concept. Similarly, Doolittle and others have argued that "the proper way to model prokaryotic evolution over 4 Gyr is as a single, albeit highly structured, recombining population, not an asexual clade."

The paper he quoted in the final sentence there is this one by Ford Doolittle, also freely available,and some of the surrounding text says,

Does LGT invalidate phylogenetics?

...

Before attempting to defuse this question (about the invalidation of phylogenetics) and sideline the debate by endorsing pluralism, I will point out some of the several ways in which the very idea of measuring the extent of LGT in realistic models (those which recognize that this process is frequent) remains problematic and vexing.

...

2. In fact, LUCA is illusory. If there is as much LGT as we WOLers think there is, the proper way to model prokaryotic evolution over 4 Gyr is as a single, albeit highly structured, recombining population, not an asexual clade. To accept this is to abandon the concept of a single tree with a single root (or at least a single rooted tree of genomes) because it means that different gene families trace to gene-family-specific ancestors that existed in different genomes at different times in the past. There will have been no single common ancestral cell whose genome harboured a direct ancestor (either the last common ancestor or their lineal predecessors) of all the genes present in all genomes today. Indeed such an ancestral cell need not have contained lineal ancestors of any of the genes around today, and is thus basically unknowable. The many attempts one still sees to reconstruct its genome are groundless, and to say the LUCA was a population is meaningless. Of course populations such as ‘all prokaryotes today’ have populations (all prokaryotes Y years ago) as their ancestors in this loose sense, but there is no principled way to designate the population at some particular value of Y as ‘LUCA’.

posted by XMLicious at 4:15 PM on March 5, 2015

sexyrobot: IIRC, the number of random chemical reactions required to spontaneously generate self-replicating molecules is so large, compared to the number of molecules in the primordial oceans that (life having arisen here so quickly after the earth cooled) the likelihood is about 50/50 that life landed here from outer space.

The bullshit handwavey part of that "statistic" is knowing the likelihood of life coming here from somewhere else. It's not 50/50; it's 50/wehavenoideawhatthisnumberis.
posted by IAmBroom at 7:49 AM on March 6, 2015

mr_roboto: LUCA was a single-celled organism; the first individual representing this organism was therefore a single cell. All other individuals of this species were descendants of this single cell (as are we all).

Again, does not follow. If one billion, essentially identical holes on the surface of some volcanic rock near a thermal vent all collected a similar proportion of non-life-originated amino acids, and 1000 of those had ideal enough conditions to form the first "lifeform", then there would be 1000 original "cells", all (potentially) of the same species.

One originating species is implied by LUCA, not one organism. Likewise, LUCA does not require that life evolved only once on Earth; instead, it states that (AFAWK) if there were others, all other life-origination events were literal dead-ends.
posted by IAmBroom at 7:54 AM on March 6, 2015

If I'm reading them correctly, the two passages I quoted above appear to indicate that in Theobald's 2010 paper he was using a definition of UCA that could involve anything between a single cell ("extremely unlikely given basic pop-gen considerations") to way beyond a single species—it sounds as though by referring to that specific part of Doolittle's paper he's implying that LUCA being the entire prokaryotic population of the planet four billion years ago, or a large chunk of it, isn't ruled out.

And then this sentence from Doolittle:

Indeed such an ancestral cell need not have contained lineal ancestors of any of the genes around today, and is thus basically unknowable.

seems like it's saying you could have a single-celled organism that via tracing back through reproduction is a common ancestor of all life currently on Earth but which doesn't actually share any genetic code with its existing descendants.

(But, I have no background in biology, so I could easily be misinterpreting all of this. Also note that Doolittle's paper was published in Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences.)
posted by XMLicious at 10:18 AM on March 6, 2015 [1 favorite]

Interesting point, XMLicious. If we accept theoretically that initial life in a given area (Planet Earth's real Eden, so to speak) would only occur in a certain way, it's conceivable that "LUCA" could be comprised of multiple ancestor-species, just as bacteria and viruses can contribute genetic material today - or the melding of the mitchondrial-RNA creature into the cells of DNA-only creatures (as a highly accepted theory).
posted by IAmBroom at 12:58 PM on March 8, 2015

Yeah, that's what I think the Doolittle quote the proper way to model prokaryotic evolution over 4 Gyr is as a single, albeit highly structured, recombining population, not an asexual clade might mean, that beyond four billion years in the past the "lateral gene transfer" method of exchanging genetic material may have been so dominant, compared to passing on genetic material in the course of reproduction, that our post-4Gyr conceptions of species and heredity are no longer valid ways of evaluating ancestry or tracing the source of the majority of a genome.

(Though note that the above quote, back in the source paper, follows the conditional "If there is as much LGT as we WOLers think there is...", so this would seem to be far from settled science.)
posted by XMLicious at 2:13 PM on March 8, 2015