When You Wish Upon a Star - Evolution News & Views

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When You Wish Upon a Star

Dr. Gerald Joyce is lonely. A researcher at Scripps Research Institute and long-time proponent of the "RNA World" hypothesis, Dr. Joyce confesses to his feelings of gloomy isolation in an article in PLoS Biology. Titled "Bit by Bit: The Darwinian Basis of Life," the paper is an odd mix of Disney-like fantasy and intelligent-design realism. PhysOrg provides a summary in which Joyce audaciously speaks for all of mankind:

"I think humans are lonely and long for another form of life in the universe," says Joyce, "preferably one that is intelligent and benevolent. But wishing upon a star does not make it so. We must either discover alternative life or construct it in the laboratory. Someday it may be discovered by a Columbus who travels to a distant world or, more likely in my opinion, invented by a Geppetto who toils at the workbench."
Even as he wishes upon a star, with a hit tip to Jiminy Cricket, Dr. Joyce knows that as a scientist he must keep his feet on the ground. Astronomers are rapidly approaching the discovery of the 1,000th extrasolar planet, yet no claims of alien life have ever panned out. Joyce continues:
Didn't President Clinton announce in 1996 that a Martian meteorite recovered in Antarctica "speaks of the possibility of life" on Mars? (No, it turned out to be mineralic artifacts.) Wasn't some "alien" arsenic-based life discovered recently in Mono Lake, California? (No, it's a familiar proteobacterium struggling to survive in a toxic environment.) Didn't Craig Venter and his colleagues recently create a synthetic bacterial cell, "the first self-replicating species we've had on the planet whose parent is a computer"? (No, its parent is Mycoplasma mycoides and its genome was dutifully reconstructed through DNA synthesis and PCR amplification.)

Why are we so confused (or so lonely) that we have such trouble distinguishing life from non-life and distinguishing our biology from another? A key limitation is that we know of only one life form, causing us to regard life from that singular perspective.... We see life as cellular, with a nucleic acid genome that is translated to a protein machinery.

In her summary of the paper, Stephanie Pappas at LiveScience agrees that the hype about habitable zones and Earth-like planets is just that: hype. She reports that Joyce feels such breathless over-reporting can backfire:
"I just worry that we cry wolf too many times, and people are going to start tuning it out," Joyce told LiveScience. "Let's just cool it on these false alarms," he added.
Science can't make an inference from a sample size of one, and Joyce knows it. In a subsection called "Rolling the Dice," he asks:
What, in fact, is the probability that a temperate, rocky planet will generate life? Science cannot say. That is because, based on the one known example of obscure origins, even a Bayesian would not want to assign a probability to such an event. The probability assessment would be more meaningful if there were even one more genuine example of life, whether discovered in space, on Earth, or in a test tube.
Reverse-Engineering Darwin

Conveniently defining life in Darwinian terms, Joyce continues:

Life self-reproduces, transmits heritable information to its progeny, and undergoes Darwinian evolution based on natural selection. Life captures high-energy starting materials and converts them to lower-energy products to drive metabolic processes. Life exists on at least one temperate, rocky planet, where it has persisted for about four billion years.
Yet, incongruously, Joyce speaks primarily of the minimum amount of information needed to comprise life. What if a system had some of the above functions, but could not evolve new functions? Would it be alive? He frames the question, again, in terms of information:
When faced with such real or hypothetical situations regarding alternative life, it is useful to frame the question in terms of information: How many heritable bits are involved, and where did they come from? ... Biological systems are distinguishable from chemical systems because they contain components that have many potential alternative compositions but adopt a particular composition based on the history of the system. In this sense biological systems have a molecular memory (genotype), which is shaped by experience (selection) and maintained by self-reproduction.
By doing some bitwork accounting and asking information-based questions, Joyce came up with a formula for the information content required for a system to be considered alive: it has to encode "more heritable bits than the number of bits required to initiate its operation." Self-replication is insufficient, he notes. A living system must have the ability to derive new information intrinsically:
Suppose one has a molecule that self-duplicates indefinitely, directing the ordered assembly of building blocks to produce additional copies of itself. That would be an interesting chemical process, but unless there is the opportunity for alternative compositions to arise and similarly reproduce -- that is, for Darwinian evolution to occur -- the bit content would be zero. Suppose one has a complex reaction cascade, perhaps even an autocatalytic cycle, contained within a growing and dividing physical compartment. That too would be an interesting chemical process, but it would not involve any heritable bits. Suppose one uses the genetic information from a preexisting biological organism to construct a facsimile that, going forward, can evolve alternative compositions. New bits could accrue within such a system, but all of the bits that were provided at the outset would have derived from the preexisting organism. To be considered a new life form, the majority of bits must be self-derived.
Life derived from a pre-existing life form would have a "privileged beginning," he says, whereas life on Earth (which he believes evolved from a primordial soup) started with zero information. He gives some examples of derivative life, but it's clear he is more interested in how to get information from the ground up.

How many bits are necessary? Joyce imagines RNA chains with 80 bits of information; that, unfortunately, would require that warm little soup to have 27 kilograms of RNA to get all the possible combinations. Things are a lot simpler, he argues, if 40 bits is considered sufficient as a starting point. Then, "a lucky milligram might contain the seed of life."

But other problems quickly mount. There's no natural selection without self-replication, and copies must be accurate enough to avoid error catastrophe. In addition, harmful cross-reactions tend to gunk up the works. (These problems were all described 28 years ago in the early ID book by Thaxton, Bradley and Olsen, The Mystery of Life's Origin.) Joyce writes:

In the laboratory one can prepare milligram quantities of random-sequence RNA molecules containing 40 or more subunits. One can provide an endless supply of activated nucleotide building blocks and control all aspects of the reaction conditions. Stacking the deck in this way, why haven't we witnessed the origin of RNA life experimentally? Because even a lucky milligram of RNA is insufficient. In order for a seed copy of replicating RNA to germinate, it must produce additional copies of itself faster than the existing copies become degraded, and it must operate with sufficient fidelity that the accurate copies are not overwhelmed by error copies. The requisite rate and fidelity of replication might reasonably be achieved in a pure reaction system that contains only the replicator and its corresponding building blocks. However, in a complex mixture of almost entirely mismatched parts, what process singles out the rare matching components? Darwinian evolution can enrich one molecule in a milligram, but before the onset of Darwinian evolution there would be only chemistry, and the chemistry of complex mixtures of cross-interacting molecules is very messy.
Show Your ID, Please

The situation seems hopeless. Dr. Joyce injects some hope by describing his own work on self-replicating RNA molecules that appear to evolve in a Darwinian fashion. But he deflates his own story by admitting he snuck information into the system:

The population of evolving RNA enzymes constitutes a synthetic genetic system, but it is limited in two important respects. First, the molecules contain only 24 bits (12 base pairs) of heritable information to encode function. Second, replication depends on 60 bits (30 defined nucleotides) that are provided at the outset and are not subject to mutation and selection.... Thus of the 84 total bits required for the system to replicate and evolve, only about one-fourth can be counted as part of the system's molecular memory. The synthetic genetic system is not a new life form because it operates mostly on borrowed bits.
At the end of the paper, under the heading "Prospects," he discusses how his loneliness might be cured. Astronomers might find alien life around another star. Evolutionists might find a new life form that derived from pre-existing life. Or, they might find life derived from bit-free chemistry. Most likely, though, he thinks, intelligent designers will reverse-engineer Charles Darwin:
Between these two extremes lie the possibilities of starting with a modest number of bits, whether by the luck of combinatorial chemistry or derived from preexisting life, then accruing enough bits within the system to be regarded as new life. Perhaps the first true alternative to terrestrial biology will be found on an extrasolar planet, in a rock from Mars, or within an extreme environment on Earth. More likely, it will be the handiwork of an intelligent species that has discovered the principles of Darwinian evolution and learned to devise chemical systems that have the capacity to generate bits on their own.
Meanwhile, scientists persist in wishing upon stars. "We can take pure chemicals in a test tube and stack the deck like crazy to try to get something replicating and evolving, and that hasn't happened yet," Joyce says. "Right now the jury's out on whether it's hard or easy." Until and unless that happens, he feels "researchers should 'hunker down' and avoid the temptation to overhype the possibility of new life forms."

And why are they tempted to overhype? "To me, it's something kind of fundamental about human loneliness," he said, speaking for all humanity again. "We just wish it to be, so that we're not alone."

As benevolent psychiatrists, let's diagnose Dr. Joyce's condition and see if we can help.

Etiology: Loneliness caused by wishing upon a star and knowing it's all hype. Symptoms aggravated by thoughts that life in the real world is information-based and runs on machinery. Condition becomes acute when pondering that Geppetto and Craig Venter are intelligent designers.

Prescription: Daily meditation on Dembski's No Free Lunch and Meyer's Signature in the Cell.

Of course, to benefit from treatment, the patient first has to realize he has a problem.