A recent article in Nature magazine presents evidence that the last universal common ancestor (LUCA) of life on Earth was probably not a hyperthermophile after all. New molecular-genetics results show the cell type all living cells can trace their own origin back to in a clear genetic line – LUCA – was not a strong heat-loving microbe. Up until now, the accepted model in evolutionary genetics was that LUCA shared most of the same traits as other highly primitive microbes on the tree of life: that they proliferate in very hot water and that they rely on iron and sulfur to drive metabolism. By that logic LUCA should be very similar to the most primitive living microbes, which are highly heat-tolerant. But this new paper, by Bastien Boussau (University of Lyon, France) and coworkers, shows that LUCA probably could not persist above about 50° C. That’s warm… but not very.
Most modern origins-of-life research has focused on examining deep sea hydrothermal vents as the most likely foci for abiogenesis. Deep sea vents are populated by the most primitive, heat-loving microbes on Earth… tiny clockwork packages of whirling mechanized RNA that can hold themselves together at up to 114° C (and probably higher), efficiently fueling their molecular nano-engines by oxidizing sulfide to sulfate, or otherwise utilizing the chemical energy in deep volcanic gases to drive their nucleic cogs. Read More
A new study by Martin A. Nowak and Hisashi Ohtsuki at Harvard University offers some interesting new perspectives on how life emerged on Earth, by examining the transition from chemistry to biology… what some might think of as the ‘primal gap’ leading from goopy organic chemistry to true Darwinian selection and evolution.
Emergence of life (EOL) research is actually a pretty big field of research, and has been since the Miller-Urey experiments decades ago. Many people in the field call it ‘emergence’ of life instead of ‘origins’ of life, because realistically the onset of life probably wasn’t a one-off event, but an emergent phenomenon that occurred in many spots around the globe in the late Hadean (about 4 billion years ago). It actually very likely that life started in many places on Earth, in different seafloor hydrothermal vent systems, and might have included several different molecular profiles using different amino acids to build different RNA variants. Read More
The European Space Agency’s COROT planet-hunter mission has identified a super-massive, high-density planet that is unlike any other exoplanet yet found. The newly discovered world COROT-exo-3b is a hot giant that circles its star once every four days, making it similar to many other ‘hot Jupiter’ giant planets already found in other star systems. What makes this one unique is its density. Based on its estimated size and mass, COROT-exo-3b would have to be over twice the density of lead. Nothing like this has ever been found before.
Gas giant planets more massive than Jupiter are common, and can range up to about 15 Jupiter masses before they begin to sluggishly fuse hydrogen in their cores to make helium – at which point they are considered brown dwarf stars. Brown dwarfs scale up from there, all the way to red dwarf stars and then ‘normal’ stars. COROT-exo-3b is different. This planet is above the mass threshold for a brown dwarf, but it’s ridiculously small for its mass – about the physical size of Jupiter. Read More
Usually my blog entries comment on some specific news item, but in other cases I’m motivated not by a particular current event or pseudoscience eruption, but by student questions or offhand comments I hear that demonstrate and remind me of some example of common bad thinking. One such example is the dramatically wrong way thermodynamics – specifically the concept of entropy – is often depicted in the popular media, in particular by opponents of evolution by natural selection.
Opponents of evolution are motivated by ignorance, and it shows. When they talk about thermodynamics and entropy, the supporters of creationism or “intelligent design” like to pretend they know something about the subject. This is really frustrating, as someone who has spent the better part of the last twenty years using thermodynamics to understand how rocks, water and bacteria interact with each other in nature. Thermo courses are almost universally feared by undergraduates and graduate students alike because of their difficulty. Even professional scientists who don’t devote sufficient attention and study can make profoundly basic mistakes when they talk about the topic. Like statistics, thermodynamics is difficult, complex, and should be used with care by the untrained. Read More
I just read a depressing article on LiveScience.com by Robert Roy Britt, discussing the limitations and flaws inherent in most public surveys about “belief” in evolution. I have to use quotation marks there, because “belief” is absolutely irrelevant. The proper term should be acceptance, as in “Do you accept the evidence of biological evolution, or are you sufficiently ignorant and narcissistic to reject an entire branch of science even though you don’t have an advanced degree in the topic?”
Britt’s article laments the imprecise ways that public surveys about evolution acceptance are worded, and goes on to suggest different approaches that pollsters could take to improve the quality and reliability of their results. All of which is fine, but it misses the point. Here is the point: we should stop using the word theory. Read More
Bio-nanotechnology appears to be moving right along, though sometimes in creepy ways…
Basic research into the origins of life continues to advance, despite the best efforts of creationists and IDiots to ignore it. Unlike the depictions presented by most evolution deniers, our understanding of prebiotic processes operating on the early Earth is actually quite advanced. Origins of life research is a vigorous field of study today and has progressed far beyond the early Miller-Urey experiments, though you wouldn’t know that from most popular media coverage of the topic. Our picture of the chain of events leading from simple organic molecules to self-replicating biomachines is still fuzzy, but nonetheless that fuzzy picture doesn’t include any blurry images of ghosts, ectoplasm or sky-giants reclining on a cloud and reaching down to engender life with a magic finger.
The consensus model in modern origins of life research is the RNA world model, in which life started as a simple RNA mechanism that could replicate itself, only later accumulating the complex bells and whistles (e.g. DNA, thousands of enzymes) that we see in the LUCA. The earliest life on Earth would have needed to operate without all those bells and whistles, using only a simple and robust complex of only a few molecules to get going. Some RNA sequences can catalyze their own replication in the absence of other enzymes, however up until now RNA studies have been unable to demonstrate sustained replication. No longer. Read More
Expectedly, the Alaskan Department of Revenue predicts further ongoing declines in proceeds from Alaskan oil. According to ADR figures,
“Alaska North Slope oil output is expected to drop 5 percent in the coming fiscal year as its oilfields age, and average prices of its crude oil are expected to fall, causing a dip in income for the state…”
This news isn’t surprising to those of us who study geology, because Alaskan oil production has been sliding steadily downward for more than a decade already. The reason has nothing to do with hippies. Alaskan oil, just like every other petroleum deposit on our planet, is finite in volume and can only be brought to the surface at a finite rate. The typical sequence of events at any oil field follows from discovery to exploratory drilling, then to extraction on an increasingly efficient and massive scale, then to maximization of delivery rate, then to decline as the subsurface stocks dwindle. Politics are irrelevant to this process; pull up oil for long enough in one place and eventually you start to hear a giant sucking sound. Pull up oil for long enough on one planet and a similar result ensues. Read More
Here’s wishing everyone a good time today, but remember that even though zombies can be fun, they can also be dangerous if you don’t know what you’re doing. So they can be very scary and make you pee on yourself, and if you do, you better go to the urologist to check what is going on. Always have an adult present when attempting to raise the dead, in case something goes wrong and instead of a harmless dancing skeleton you accidentally summon up a horde of terrifying revenants bent on consuming the life force of all humanity. Please be courteous to others and always dispel your zombies when you’re done with them. It only takes a few moments to clean up your mess by filling the mouth with salt and sewing it shut, then cutting off the head before disposing of your zombie safely in an approved container.