CapitalistImperialistPig

Geoffrey Miller has a theory about Fermi's paradox . Seventy years or so ago, a bunch of physicists were wondering about the plausibility of extra-terrestial intelligence. It was obvious already that there were lots of stars, and it seemed likely that many of them had planets. Once intelligent life had evolved, it shouldn't take long to colonize a galaxy. Fermi listened patiently, then asked, simply, “So, where is everybody?” That is, if extraterrestrial intelligence is common, why haven’t we met any bright aliens yet? This conundrum became known as Fermi’s Paradox. The paradox has gotten somewhat sharper since. We have now discovered hundred of extraterrestial planets, and it's clear that they are pretty common. It's plausible, if not yet demonstrated, that there are many which are good candidates for supporting life. The evolution of life and especially intelligence is more problematic - it took a long time here on Earth. Still it's plausible - again not y...

The toughest problem in evolution has always been origins. Once scientists figured out the way the skills of life were partitioned among DNA, RNA and proteins, the question became how the whole complex system could have originated. Bacterium, yeast, tree, worm, dinosaur and human looked pretty different until we started figuring out how they all worked, but once we had they all started looking pretty similar. Inside each is (almost) the very same system of DNA genes, RNA helpers and proteins, doing the same things to keep us all alive. This fact is stupendously obvious signal of the common origin of all life, but it’s a lot more silent on the question of what those origins were. We have a pretty clear if imperfect picture of how tree and dinosaur evolved out of bacteria, but we have many fewer clues as to how the first bacteria evolved out of non-living chemicals. The real problem is that neither contemporary life nor the fossil record has preserved anything much in the way of in...

The Drake equation is an attempt to estimate the probability of contacting intelligent life on other planets, or, more generally, the probability that intelligent life exists on other planets. It is expressed as a product of a bunch of probabilities all of which were largely unknown when it was formulated nearly fifty years ago. Some of the more important were the fraction of stars with planets, the fraction of planets that were Earth like, and the probability of life arising on an Earth like planet - all of which were squarely in the unknown category a half century ago. Many hundreds of planets have now been discovered around nearby stars, and a significant fraction of them are apparently Earth like in size at least. One investigator suggested something like 100 million Earth like planets in the Galaxy - about one for every 1000 stars. The probability of life arising on such a planet is still unknown, but there are increasingly strong hints that it could be substantial. That still le...

It's hard to imagine a scientific question more exciting than that of the origin of life, and Discover Magazine has a new article on a provocative new theory. That theory posits an origin in ice at very cold temperatures. This notion is counterintuitive but there is evidence from experiments, and if true, suggests that the chances for life elsewhere in the solar system and cosmos might be very good. Some of the most provocative experiments were done by Stanley Miller, the famous origin of life pioneer. One morning in late 1997, Stanley Miller lifted a glass vial from a cold, bubbling vat. For 25 years he had tended the vial as though it were an exotic orchid, checking it daily, adding a few pellets of dry ice as needed to keep it at –108 degrees Fahrenheit. He had told hardly a soul about it. Now he set the frozen time capsule out to thaw, ending the experiment that had lasted more than one-third of his 68 years. Miller had filled the vial in 1972 with a mixture of ammonia and c...

Iris Fry's book The Emergence of Life on Earth: A Historical and Scientific Overview is a detailed but non-technical account of attempts to explain how life emerged from non-living material. I have posted a number of articles on the book and closely related subjects here . I liked the book a lot, and much of the material was new to me, even though I have long been interested in the subject. Fry is a clear and careful writer, and there are endnotes enough for any scholar - the book includes a sixteen page bibliography. At first I was a bit suspicious of her historical and philosophical point of view, but in retrospect, it is an excellent vantage point. Although a good portion of the book is "ancient history," that is, prior to 1953 and the molecular biology revolution, the majority is focussed on the developments since. She excels at concisely presenting the perspectives and starting points of major investigators, and they are highly various. Like the fabled blind men of ...

The toughest problem in defining a general theory of life is the paucity of examples. That statement sounds like an oxymoron - isn't life famously diverse? Man, elephant, mouse, carrot, redwood, mushroom, coral, sponge, and bacterium seem pretty darn different. At the molecular level, however, they aren't. The most essential machinery at the molecular level is almost exactly the same. They all use the same genetic code, and the same basic mechanisms for the most basic operations of life. These commonalities, and the patterns of both commonalities and differences constitute the most dramatic proof of the fact of common descent. However all that common machinery came into existence, it all seems to have existed in the most recent common ancestor of all known Earthly life. Despite a large number of apparently contingent and arbitrary elements in life, exceptions are not known. Proteins and complex sugars have definite chiralities but we don't know of any fundamental r...

Comments upon reading Iris Fry's The Emergence of Life on Earth Chapters 9-11 Which came first: the chicken or the egg? That is the fundamental question in the origin of life. Evolution manages to kick this can down the road a bit: the chicken and egg evolved together from earlier egg layers which in turn evolved from more primitive reproduction schemes. We even have samples of the more primitive reproduction schemes around to encourage us. The discovery that life processes could be reduced to biochemistry, together with the Oparin-Haldane hypothesis positing a reducing atmosphere for the primeval Earth, encouraged origin of life researchers to believe that organic chemistry might naturally produce the molecules of life. However, developments from 1960 to the nineteen-eighties put a couple of severe dampers on such optimism. First, and probably most grievously, explication of the mechanisms of heredity and metabolism revealed an intrinsic complexity that seemed guaranteed to preve...

Cycles are pretty common in the Universe. Galaxies go through cycles of star formation and decay. Atoms are cycled through stars and back into the interstellar medium. Here on Earth, we have the hydrological cycle, with water evaporating from the oceans or elsewhere, condensing and falling as precipitation, and flowing back to the ocean. Oceanic crust and other materials from the interior of the planet is extruded at mid-ocean rifts and volcanos, cycled across oceans and subducted back into the interior. Oxygen and carbon atoms have their own cycles through rock, ocean, and atmosphere. Closest to our interest here are the cycles of life. Birth, growth, death and decay take place in a cosmic instant, but these cycles have something crucial in common with all the others - they are all heat engines, powered by taking in energy at low entropy and putting it out at higher entropy. The same of course is true of the cycle that powers your automobile. All the cycles mentioned are in s...

Arun, writing in the comments to an earlier post, brought my attention to Robert Shapiro's Scientific American cover story on a metabolism first approach to the origin of life. (Subscription only, but a longer, earlier, free version, minus nifty graphics and some other features is here. ) The magic without magic of small molecule cycles is heredity without heredity - actually, a distributed type of heredity. Such a system takes energy from the environment, uses it to drive a chemical cycle which includes producing more of the molecules that participate in the cycle. In effect, such systems create a local negative entropy gradient by exploiting some naturally occuring negative entropy gradient (energy from the Sun, volcanos, lightning, whatever). Hurricanes perform an analogous feat. Once organized, their ferocious winds very efficiently extract heat from the ocean and use it to drive those same winds. The entropy gradient they exploit is that between the warm ocean below and the...

Comments upon reading Iris Fry's The Emergence of Life on Earth Chapters 7 & 8 The discovery of the structure of DNA in 1953 by Watson and Crick (with large contributions from Maurice Wilkins, Rosalyn Franklin, and Linus Pauling, to mention a few) is perhaps the most momentous discovery of the twentieth century. Watson, Crick, and Wilkins got the Nobel, and most of the glory (Franklin was already dead, and Pauling, who came close but missed, already had two of his own) but it is clear that if Watson and Crick had failed, somebody else would have discovered it soon, regardless. The most important fact that discovery revealed was noted in the very coy finale of the Watson and Crick publication: “. . . it has not escaped our attention that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material”. The DNA structure consists of two complementary helices, which upon separation, can produce (with the help of enzymes) two co...

Reading Iris Fry's The Emergence of Life on Earth Chapter 6 Not much progress on understanding the origin of life was possible until some understanding of the mechanisms of life was achieved. Some physics and a lot of chemistry were required before it could be discovered how living things went about the business of growing, developing, and reproducing. Underlying all living activity is metabolism - the systematic production of chemical changes that consumed energy, changed its form, and used it to produce motion or new components of living things. It gradually became understood that highly specific catalysts (enzymes) were the master chemists at work in living cells. Meanwhile, Mendel's laws of genetics had made possible an "atomic theory" of inheritance. Heredity was apparently embodied in discrete form, rather than as some mysterious and continuously variable fluid. Leonard Trolland, writing in 1914, realized that a gene too could be considered a sort of catalyst -...

That evocative phrase of the physicist John Archibald Wheeler is probably even more apropos for biology than for physics. The problem in biology was the seeming unbridgeable gap between living and non-living. From Aristotle to Descartes to Huxley, biologists were forced to invoke some magic - some vital principle mysteriously present in organic matter - in order to explain life. Of course Descartes and Huxley tried to reduce it to mechanism, but always their ideas collided with the complexity and purposefulness of life. Leonardo da Vinci conceived of biological systems as machines at least 500 years ago, and Descartes made it a cornerstone of his philosophy a bit more than a century later, but three plus centuries more were needed before biology (and physics, chemistry and biochemistry) could penetrate to the essence of that magic. That magic without magic is modern molecular biology, especially the revelation of the workings of DNA and its translation into proteins. Only with that ...

The reductionist paradigm bequeathed to us from the ancient Greek philosophers always had trouble with life. Aristotle found it necessary to invoke a dualistic explanation, dividing the world into body and soul, matter and an organising priciple. Iris Fry, in her book The Emergence of Life on Earth , devotes the first five chapters to the historical background of thought on the origin of life, and Aristotle's idea, suitably kneaded and pummeled, formed the foundation until nearly the beginning of the twentieth century. Actually, even today it's hard to take much exception to Aristotle, except that we now know that the organizing principle, or soul, is embodied in the information stored in material, the DNA. Although early Greek atomists resisted making a distinction between living and nonliving, the difference is simply too marked to be ignored. The problem that now bedevils us, abiogenesis, or the development of life from non-living material, wasn't a problem for much ...