Darwin in the Air
Darwin Day euphoria must be in the air. There have been several news stories with Darwin or Evolution in the title, but little to his credit in the substance of the article.
- Evolution inaction: The human immune system is, by any account, Science Daily, however not only called it a case of “Evolution in Action,” but claimed the immune system makes “evolutionary leaps” to fight microbes. Gerald Weissmann, editor of the journal FASEB, ended with this line: “Nowadays, mosquitoes, parasites and viruses cause diseases in the United States that were once isolated to warmer parts of the world. They evolve, and – a la Darwin – so does our immune system each time we meet a new microbial invader.” Would you like your immune system with Darwin or without?
- Facile fossils: The Cambrian Explosion has been called “Darwin’s Dilemma” in that all the major animal body plans show up in the Cambrian layers without precursors. Science Daily announced that a solution has been found. One reads the article eagerly only to find fossil microbes in the Precambrian, something that was already known, and has little or no bearing on the origin of animal body plans.
- Cool OOL: PhysOrg and other news sites announced that scientists have created an RNA molecule with enzymatic capabilities that replicates itself indefinitely. The folks at Scripps Research Institute are using their creation to speculate on the origin of life and the genetic code. “This is the only case outside biology where molecular information has been immortalized,” said Gerald Joyce, leaving aside the question of what constitutes information. One other little problem is getting RNA in the first place (see 08/23/2005). For more problems with the “RNA World” scenario, as revealed by Gerald Joyce earlier, see the 07/11/2002 entry.
Nevertheless, the Scripps team found it “extremely interesting” that their creations could also mutate and yet some would breed true. “The research shows that the system can sustain molecular information, a form of heritability, and give rise to variations of itself in a way akin to Darwinian evolution.” This is “knocking on the door of life,” Joyce teased. He did admit that the molecule lacks the ability to do anything. That makes it doubtful it could be compared to life. What’s more, Science Daily said that the subunits in their manufactured molecule “each contain many nucleotides, so they are relatively complex and not something that would have been found floating in the primordial ooze.” It appears the information in their molecules was intelligently designed.
- Darwin’s reverse gear: “Reverse evolution” was the tag line in another story on Science Daily. “Scientists have turned back the clock on the evolution in the fruit fly to provide key insights into the basic mechanisms of evolution,” it says. In a strange twist of terms invoking design and creation in an evolutionary story, the article claims that researchers “recreated natural selection in real-time” and showed that contingency matters. What is reverse evolution, you ask? The team put fruit flies that had passed through several generations in the lab back into the wild. Then they looked for changes in one chromosome and found about 50% of the changes in the lab reverted to wild type. Even though they started with fruit flies and ended with fruit flies, this supposedly proved that “evolution is contingent upon history at the genetic level” as well as the phenotypic level. This made the team feel they had gained “further insights into the basic understanding of how evolution and diversity are generated and maintained.”
- Evolutionary leaps: Darwin had claimed that natural selection could never make a great leap, but must always proceed by slow but sure steps. Maybe if the leaps are stretched out over millions of years they are not really leaps. Science Daily last month claimed that “Life On Earth Got Bigger In 2-million-fold Leaps.” Assuming common ancestry as fact, the article began, “Earth’s creatures come in all sizes, yet they (and we) all sprang from the same single-celled organisms that first populated the planet. So how on Earth did life go from bacteria to the blue whale?” Good question. The answer, according to Jonathan Payne at Stanford, is that “It happened primarily in two great leaps, and each time, the maximum size of life jumped up by a factor of about a million.” How did they find that out? Combing through databases of genomes and fossils, they noticed explosions of size. “The first jump in maximum size happens when the first eukaryotic organisms show up as fossils,” they said. Payne explained, “The fossil record indicates pretty clearly that you need a eukaryotic cell to make that first size jump.” He left invention to that necessity; apparently evolution provided whatever was needed.
Once you have eukaryotes, potential for evolutionary creativity is awakened. But millions of years passed with not much change in organismal size. “Then about 600 million years ago, at the same time as another major boost in the amount of oxygen in the atmosphere, life leaped in size again” by a million fold (referring to the Cambrian Explosion). What happened to cause this? “the real explosion of size increase didn’t happen until the oxygen level bumped up.” True, oxygen is necessary for explosions, but those are usually destructive. “So why do the size leaps seem to hinge on the amount of oxygen in the air?” Another good question. “There are a few things that could be going on,” Payne rambled, but his scenario called for complex mechanisms to use the oxygen for metabolism. Microbes, in the story, did this for millions of years without leaping in size a million-fold. “The possible causes of the second jump in oxygen are less clear, Payne said, but regardless of the puzzles that remain to be sorted out, the timing and magnitude of the jumps up in maximum size are clear,” that is, if one accepts the evolutionary timeline. Whatever it was, it affected a lot of things simultaneously – i.e., all the animal phyla in a geological instant.
What Darwin had to do with any of this other than lending his name and reputation was also less clear. One thing his name did provide was an opportunity for storytelling. The last article had Payne speculating on this question: “Can we look forward to another great leap in size? Will we see housecats larger than our houses?” Tune in next time, when we see if the size of the earth and the presence of humans makes tyranno-cats unlikely.
Darwine is a potent psychedelic potion that lubricates the imagination. It simultaneously works as a strong laxative, but what comes out is hard to call science.