• Dimijian opens his article with the statement that, "Evolutionary theory has never had a stronger scientific foundation than it does today." He cites "the deep commitment of today's biologists to Darwinian natural selection and to discoveries made since Darwin's time." Ironically, Darwinian natural selection is under attack in the mainstream biological literature perhaps more today than it has been in many decades. We recently covered some of these critics of natural selection here. As journalist Susan Mazur observed after interviewing many scientists about the Altenberg 16 conference, there are "hundreds of other evolutionary scientists (non-creationists) who contend that natural selection is politics, not science, and that we are in a quagmire because of staggering commercial investment in a Darwinian industry built on an inadequate theory." 1 Likewise, Joseph Kuhn observes, "over 800 PhD scientists have signed a letter stating their concerns about the full scope of Darwinian evolution."



• Dimijian cites the classic icon of evolution, the Galápagos finches, stating: "There is no contender for causation other than natural selection." But no Darwin-critic has ever stated otherwise. In fact, it seems likely that natural selection is a real force affecting the Galápagos finches, but its effects have been trivial. As Robert J. Whittaker's treatise Island Biogeography states, "it is extremely difficult to identify all the [Galápagos] finches, as the largest members of some species are almost indistinguishable from the smallest members of others." 2 Dimijian suggests the finches represent "fast-track evolution," even though a paper in BioScience notes that the finches "retain the ability to interbreed and produce viable, fertile hybrids" -- after millions of years of evolution! 3



• He cites animal breeding experiments as supposedly demonstrating the power of natural selection, but fails to note the limits encountered by breeders. As the textbook Explore Evolution explains:

  For the critic, the question is not whether sheep can become woollier sheep; the question is whether sheep can eventually become sheepdogs... or horses... or camels. In other words, can natural selection transform one form of life into a fundamentally different form of life? ... Critics say that the experimental evidence reveals definite, discoverable limits on what artificial selection can do. They point out that animal breeders hit limits all the time. Breeders have tried for decades to produce a chicken that will lay more than one egg per day. They have failed. Horse breeders have not significantly increased the running speed of thoroughbreds, despite more than 70 years of trying. Darwin's theory requires that species have an immense capacity to change, but the evidence from breeding experiments shows that there are definite limits to how much a species can change, even when intelligent agents (the breeders) are doing the selection intentionally, trying to maximize certain traits. 4

• Dimijian offers other unimpressive evidence like the "eyes in some cave-dwelling fishes," so-called "vestigial genes," antibiotic resistance, or what he calls "hundreds of fossils of feathered dinosaurs." But he makes no mention of scientific debates over these claims, with functions being discovered for pseudogenes and ERVs, and evidence that "feathered dinosaurs" are really secondarily flightless birds. Nor does he seem to be aware that no Darwin-skeptic disputes the evidence of blind-eyed cave fish. Instead, skeptics observe that these loss-of-function examples are well-within the edge of evolution. Dimijian makes no mention that antibiotic resistance entails trivial genetic changes and often comes at a cost to fitness .



• He gives simplistic, speculative arguments like "The transition from scales to feathers may have hinged on a relatively simple genetic switch," even though the scales-to-feathers hypothesis has been abandoned by leading evolutionary theorists. He cites Tiktaalik, claiming, "Play the fossil frames in a movie sequence and you see the emergence of fishes onto land," failing to note the large morphological gap between fishes like Tiktaalik and true tetrapods, and failing also to note that some of the "fossil frames" -- like true tetrapods that predate Tiktaalik -- are badly out-of-order.



• He tries to solve the enigma of the Cambrian explosion by citing molecular clock data showing an ancient origin of animals -- though an accurate understanding of this data simply shows that living animals have a much larger degree of genetic differences than allowed by the fossil record. In any event, molecular clock data is highly controversial. As Joseph Kuhn wrote in response to another one of his critics:
  
  

  [M]olecular clocks have been shown to be a variable and unsteady process, requiring a host of assumptions that are not widely accepted, including the assumption that the organisms are related in the first place. As one paper in Annual Review of Earth and Planetary Sciences recognized, "The second area where molecules and morphology are in serious disagreement concerns the origins of the metazoan phyla. . . . The discord between the two for the animal phyla may be as much as 500 million years," and concluded, "the idea that there is a universal molecular clock ticking away has long since been discredited." A 2006 article in Biological Therapy stated that a "review of the history on molecular systematics and its claims in the context of molecular biology reveals that there is no basis to the 'molecular assumption.'" Moreover, molecular clocks simply assume that any genetic similarity results from common ancestry; they do not demonstrate that is the case. My article indicated that there are paleontologists who feel strongly that the fossil data do not fully support Darwinian evolution. As Nature editor Henry Gee commented, "To take a line of fossils and claim that they represent a lineage is not a scientific hypothesis that can be tested, but an assertion that carries the same validity as a bedtime story -- amusing, perhaps even instructive, but not scientific." Thus, the fossil data remain controversial based on abrupt formation of species, less-than-convincing missing links (transitional species), and variable and assumption-laden conclusions of molecular clocks. (internal citations removed)

• Dimijian recapitulates the standard story of human origins, failing to note the large morphological gap between human-like and ape-like species in the fossil record, and recounts the highly disputed Savannah grassland hypothesis for the origin of human bipedalism.

Even Miller throws up his hands at certain aspects of it. The first step, making the monomers, that's easy. We understand it pretty well. But then you have to make the first self-replicating polymers. That's very easy, he says, the sarcasm fairly dripping. Just like it's easy to make money in the stock market -- all you have to do is buy low and sell high. He laughs. Nobody knows how it's done. 5

[M]odern geochemists doubt that a "primordial soup" existed. He made the mistake that origin-of-life researcher David Abel warned against: "Mere possibility is not an adequate basis for asserting scientific plausibility," and "just because a hypothesis is possible should not grant that hypothesis scientific respectability." In this case, the odds of producing a self-replicating RNA molecule go beyond the available probabilistic resources. (internal citations removed)

Nucleotides, for example, are not encountered in nature beyond organisms or laboratory synthesis. To construct RNA, high concentrations of four select nucleotides would be needed in the same location, with others being excluded. If this is the prerequisite for life, then it is an unusual phenomenon, rare in the Universe. 7

However, Robert Shapiro, professor emeritus of chemistry at New York University disagrees. "Although as an exercise in chemistry this represents some very elegant work, this has nothing to do with the origin of life on Earth whatsoever," he says. According to Shapiro, it is hard to imagine RNA forming in a prebiotic world along the lines of Sutherland's synthesis. "The chances that blind, undirected, inanimate chemistry would go out of its way in multiple steps and use of reagents in just the right sequence to form RNA is highly unlikely," argues Shapiro. Instead, he advocates the metabolism-first argument: that early self-sustaining autocatalytic chemosynthetic systems associated with amino acids predated RNA. 8

Although newspapers and high school biology texts often assert (without providing detail) an RNA-world hypothesis, there are strongly dissenting scientists who argue that the essential RNA polymerase enzyme does not form by itself. Stephen Meyer listed additional insurmountable obstacles to an RNA first hypothesis: 1) the inability to account for the necessary nucleotides or ribose molecules (they don't form spontaneously), 2) the nonfunctional early ribosome, 3) the nonexistent RNA translation and coding system, and 4) the origin of the inherent genetic information. He specifically stated, "RNA-first theories, like their predecessors, had failed to explain the central question of the origin of the 'information' that living cells require." (internal citations omitted)

Dr. Hansen chose to use ad hominem arguments, charging that I am a "religious creationist." His attacks are inaccurate, and any aspersions to my religion are irrelevant, as I did not make any theological arguments. I am just a surgeon with experience in molecular medicine and with respect for objective scientific inquiry.

• Robert Carroll stated in the leading journal Trends in Ecology and Evolution that "within less then 10 million years, almost all of the advanced phyla appeared, including echinoderms, chordates, annelids, brachiopods, molluscs and a host of arthropods. The extreme speed of anatomical change and adaptive radiation during this brief time period requires explanations that go beyond those proposed for the evolution of species within the modern biota." 9



• Likewise, an article in the journal Development by three Cambrian explosion experts explains that, "The Cambrian explosion is named for the geologically sudden appearance of numerous metazoan body plans (many of living phyla) between about 530 and 520 million years ago, only 1.7% of the duration of the fossil record of animals." 10
  
  
  
  
• Another article in a major evolution journal states that "recent geological investigations suggest that the Cambrian explosion may have occurred within a period of only 5-10 million years." 11

[Jones] is incorrect in his assessment of the current state of affairs regarding prebiotic molecules research. I would acknowledge an enormous amount of modern research into molecular chemistry, hydrothermal vents, lipid formation, and many aspects of prebiotic science. But many of these ideas have problems. To take hydrothermal vents, for one, they would serve as a poor location for the origin of life to take place since their high heat would quickly degrade any organic molecules. As William Dembski noted, "Most of origin-of-life research is as relevant to the real problem of life's origin as rubber-band powered propeller model planes are to the military's most sophisticated stealth aircraft." In other words, there is not a single paper that has demonstrated the autoformation of DNA, RNA, or a functioning cell.

The articles I cited are from mainstream scientific sources. Some Darwinists have a certain degree of indoctrination that makes it difficult for them to accept papers that are critical of their "paradigm." These papers have raised specific concerns about the ability of Darwinian evolution to explain (a) the origin of DNA, (b) the origin of the cell, and (c) the inability of irreducibly complex systems to form in a step-by-step fashion.

We also select XNA aptamers, which bind their targets with high affinity and specificity, demonstrating that beyond heredity, specific XNAs have the capacity for Darwinian evolution and folding into defined structures. Thus, heredity and evolution, two hallmarks of life, are not limited to DNA and RNA but are likely to be emergent properties of polymers capable of information storage.

• The scientists selected the aptamers.
• The scientists selected the targets.
• The scientists selected the defined structures.

• A capacity for Darwinian evolution is not a demonstration of it.
• The likelihood of emergent properties is not a demonstration of it.
• The capability for information storage is not a demonstration of it.

These studies have revealed the profound influence of backbone, sugar, and base chemistry on nucleic acid properties and function. Crucially, only a small subset of chemistries allows information transfer through base pairing with DNA or RNA, a prerequisite for cross-talk with extant biology. However, base pairing alone cannot conclusively determine the capacity of a given chemistry to serve as a genetic system, because hybridization need not preserve information content. A more thorough examination of candidate genetic polymers' potential for information storage, propagation, and evolution requires a system for replication that would allow a systematic exploration of the informational, evolutionary, and functional potential of synthetic genetic polymers and would open up applications ranging from biotechnology to materials science.

Here, we describe a general strategy to enable enzymatic replication and evolution of a broad range of synthetic genetic polymers based on: (i) a chemical framework [generically termed xeno-nucleic acid (XNA)] capable of specific base pairing with DNA, (ii) the engineering of polymerases that can synthesize XNA from a DNA template, and (iii) the engineering of polymerases that can reverse transcribe XNA back into DNA.

Our work establishes strategies for the replication and evolution of synthetic genetic polymers not found in nature, providing a route to novel sequence space. The capacity of synthetic polymers for both heredity and evolution also shows that DNA and RNA are not functionally unique as genetic materials. The methodologies developed herein are readily applied to other nucleic acid architectures and have the potential to enable the replication of genetic polymers of increasingly divergent chemistry, structural motifs, and physicochemical properties, as shown here by the acid resistance of HNA aptamers (fig. S17). Thus, aspects of the correlations between chemical structure, evolvability, and phenotypic diversity may become amenable to systematic study. Such "synthetic genetics" -- that is, the exploration of the informational, structural, and catalytic potential of synthetic genetic polymers -- should advance our understanding of the parameters of chemical information encoding and provide a source of ligands, catalysts, and nanostructures with tailor-made chemistries for applications in biotechnology and medicine.

Genetics provides a mechanism for molecular memory and thus the basis for Darwinian evolution. It involves the storage and propagation of molecular information and the refinement of that information through experience and differential survival. Heretofore, the only molecules known to be capable of undergoing Darwinian evolution were RNA and DNA, the genetic molecules of biology. But on page 341 of this issue, Pinheiro et al. expand the palette considerably. They report six alternative genetic polymers that can be used to store and propagate information; one of these was made to undergo Darwinian evolution in response to imposed selection constraints. The work heralds the era of synthetic genetics, with implications for exobiology, biotechnology, and understanding of life itself.

Nevertheless, the spontaneous arrival of RNA through a sequence of purely random mixing events of primitive chemicals was at the very least, an unlikely occurrence. "This is a big question," Chaput says. "If the RNA world existed, how did it come into existence? Was it spontaneously produced, or was it the product of something that was even simpler than RNA?"

This pre-RNA world hypothesis has been gaining ground, largely through investigations into XNAs, which provide plausible alternatives to the current biological regime and could have acted as chemical stepping-stones to the eventual emergence of life. The current research strengthens the case that something like this may have taken place.