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Archive for the ‘Evolution’ Category

Animal Copies Reveal Roots of Individuality

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Emily Singer has a very interesting article in Quanta:

Benjamin de Bivort’s lab at Harvard University is Groundhog Day for fruit flies. In de Bivort’s version, a fly must choose to walk down a dark tunnel or a lighted one. Once it has made the choice — THWOOP! — a vacuum sucks the fly back to the starting point, where it has to decide again… and again… and again.

The contraption, which tracks scores of individual flies, makes it possible to analyze how behavior varies from fly to fly. What de Bivort found when he first used it surprised him: The animals’ behavior varied much more than he expected, even when the flies were more or less genetically identical and raised under the same conditions. “If you hold genetics constant and the environment mostly constant, you still see a lot of variation,” de Bivort said.

De Bivort and his team are now exploring this phenomenon in detail, hoping to discover what drives that unexpected individuality. He’s found that different fly strains show different levels of variability. Some strains are like a troop of well-trained soldiers, with each fly mirroring its neighbor. Other strains resemble a wild group of dancers, with individuals moving to their own beat. By comparing soldier and dancer strains, de Bivort thinks he’s identified both a gene and a neural circuit that may underlie some of these differences.

“They are suggesting that variation itself might be a genetic trait,” said Gerd Kempermann, a neurobiologist at the German Center for Neurodegenerative Diseases in Dresden. “That’s a new and interesting twist.” In other words, natural selection might sometimes favor genetic variants that produce a mix of behaviors — the wild dancers — over variants that create the same outcomes.

De Bivort’s work is part of a larger effort to understand why nature produces so much variability. Is it merely a side effect of the random mutations that affect all living things? Or does natural selection reward variability and favor mutations that produce it? A diverse population might be more likely to survive changing conditions. A stand of trees that seeds at different times during the season is more resistant to an early frost or late rains than one that disperses all its seeds at once.

“Whether variance itself is a trait that can vary among individuals or genotypes has important implications and is potentially fascinating, but is very difficult to study,” said Alison Bell, a biologist at the University of Illinois, Urbana-Champaign. Comparing genetically identical, or almost identical, lines of flies, as de Bivort is doing, “is really the best tactic for getting at this question.”

A Bad Breed

Buff Orpington chickens are the lapdogs of the chicken world, known for their extreme friendliness. But the breed occasionally hatches an ornery clucker, much to breeders’ dismay. The Buffs aren’t alone.

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Written by LeisureGuy

13 May 2015 at 11:19 am

Posted in Evolution, Science

How Structure Arose in the Primordial Soup

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It is becoming increasingly clear that life is an inevitable outcome given the right conditions. Emily Singer in Quanta recounts some of what we know about the first steps:

About 4 billion years ago, molecules began to make copies of themselves, an event that marked the beginning of life on Earth. A few hundred million years later, primitive organisms began to split into the different branches that make up the tree of life. In between those two seminal events, some of the greatest innovations in existence emerged: the cell, the genetic code and an energy system to fuel it all. All three of these are essential to life as we know it, yet scientists know disappointingly little about how any of these remarkable biological innovations came about.

“It’s very hard to infer even the relative ordering of evolutionary events before the last common ancestor,” said Greg Fournier, a geobiologist at the Massachusetts Institute of Technology. Cells may have appeared before energy metabolism, or perhaps it was the other way around. Without fossils or DNA preserved from organisms living during this period, scientists have had little data to work from.

Fournier is leading an attempt to reconstruct the history of life in those evolutionary dark ages — the hundreds of millions of years between the time when life first emerged and when it split into what would become the endless tangle of existence.

He is using genomic data from living organisms to infer the DNA sequence of ancient genes as part of a growing field known as paleogenomics. In research published online in March in the Journal of Molecular Evolution, Fournier showed that the last chemical letter added to the code was a molecule called tryptophan — an amino acid most famous for its presence in turkey dinners. The work supports the idea that the genetic code evolved gradually.

Using similar methods, he hopes to decipher the temporal order of more of the code — determining when each letter was added to the genetic alphabet — and to date key events in the origins of life, such as the emergence of cells.

Dark Origins

Life emerged so long ago that even the rock formations covering the planet at that time have been destroyed — and with them, most chemical and geological clues to early evolution. “There’s a huge chasm between the origins of life and the last common ancestor,” said Eric Gaucher, a biologist at the Georgia Institute of Technology in Atlanta.

Scientists do know that at some point in that time span, living creatures began using a genetic code, a blueprint for making complex proteins. It is those proteins that carry out the vital functions of the cell. (The structure of DNA and RNA also enables genetic information to be replicated and passed on from generation to generation, but that’s a separate process from the creation of proteins.) The components of the code and the molecular machinery that assembles them “are some of the oldest and most universal aspects of cells, and biologists are very interested in understanding the mechanisms by which they evolved,” said Paul Higgs, a biophysicist at McMaster University in Hamilton, Ontario.

How the code came into being presents a chicken-and-egg problem. The key players in the code — DNA, RNA, amino acids, and proteins — are chemically complicated structures that work together to make proteins. But in modern cells, proteins are used to make the components of the code. So how did a highly structured code emerge?

Most researchers believe that the code began simply with basic proteins made from a limited alphabet of amino acids. It then grew in complexity over time, as these proteins learned to make more sophisticated molecules. Eventually, it developed into a code capable of creating all the diversity we see today. “It’s long been hypothesized that life’s ‘standard alphabet’ of 20 amino acids evolved from a simpler, earlier alphabet, much as the English alphabet has accumulated extra letters over its history,” said Stephen Freeland, a biologist at the University of Maryland, Baltimore County.

The earliest amino acid letters in the code were likely the simplest in structure, those that can be made from purely chemical means, without the assistance of a protein helper. (For example, the amino acids glycine, alanine and glutamic acid have been found on meteorites, suggesting they can form spontaneously in a variety of environments.) These are like the letters A, E and S — primordial units that served as the foundation for what came later.

Tryptophan, in comparison, has a complex structure and is comparatively rare in the protein code, like a Y or Z, leading scientists to theorize that it was one of the latest additions to the code.

That chemical evidence is compelling, but circumstantial. Enter Fournier. He suspected that by extending his work on paleogenomics, he would be able to prove tryptophan’s status as the last letter added to the code.

The Last Letter

Scientists have been reconstructing ancient proteins for more than a decade, primarily to figure out how ancient proteins differed from modern ones — what they looked like and how they functioned. But these efforts have focused on the period of evolution after the last universal common ancestor (or LUCA, as researchers call it). Fournier’s work delves further back than any other previous efforts. To do so, he had to move beyond the standard application of comparative genomics, which analyzes the differences between branches on the tree of life. “By definition, anything pre-LUCA lies beyond the deepest split in the tree,” he said.

Fournier started with two related proteins, TrpRS (tryptophanyl tRNA synthetase) and TyrRS (tyrosyl tRNA synthetase), which help decode RNA letters into the amino acids tryptophan and tyrosine. TrpRS and TyrRS are more closely related to each other than to any other protein, indicating that they evolved from the same ancestor protein. Sometime before LUCA, that parent protein mutated slightly to produce these two new proteins with distinct functions. Fournier used computational techniques to decipher what that ancestral protein must look like.

He found that the ancestral protein has all the amino acids but tryptophan, suggesting that its addition was the finishing touch to the genetic code. “It shows convincingly that tryptophan was the last amino acid added, as has been speculated before but not really nailed as has been done here,” said Nigel Goldenfeld, a physicist at the University of Illinois, Urbana-Champaign, who was not involved in the study.

Fournier now plans to use tryptophan as a marker to date other major pre-LUCA events such as the evolution of metabolism, cells and cell division, and the mechanisms of inheritance. These three processes form a sort of biological triumvirate that laid the foundation for life as we know it today. But we know little about how they came into existence. “If we understand the order of those basic steps, it creates an arrow pointing to possible scenarios for the origins of life,” Fournier said.

For example, . .

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Written by LeisureGuy

16 April 2015 at 12:48 pm

Posted in Evolution, Science

Denmark’s Drug-Free Pigs

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Barry Estabrook writes in the NY Times:

PRESIDENT OBAMA didn’t need to issue a $1.2 billion National Action Plan for Combating Antibiotic-Resistant Bacteria, which he did last week, to figure out how the United States could reduce the antibiotic-resistant bacteria created by the country’s agriculture industry. He could have simply spent a day with Kaj Munck, a Danish hog farmer.

Mr. Munck is a husky, loquacious man who lives about an hour south of Copenhagen. His operation looks and smells a lot like the factory pig farms I have visited in the American Midwest. The 12,000 pigs he raises each year — making his operation larger than the average American producer — live in cramped stalls with hard floors inside low-slung warehouselike structures. Mr. Munck can produce pork at prices low enough to compete in the same international markets as American pork. In fact, a large number of the popular baby back ribs served in the United States are imported from Danish farms like his.

But there is one big difference between Danish hog farms and those in the United States that does meet the eye (or nose). Since 2000, Danish farmers have raised pigs without relying on regular doses of antibiotics — while in the United States, perfectly healthy pigs and other livestock are frequently given low levels of antibiotics in their food or water to prevent disease, a practice that also enhances their growth.

Such regular doses of antibiotics contribute to the development of drug-resistant “superbugs,” of the type that kill 23,000 Americans a year, according to the Centers for Disease Control and Prevention. One goal of the National Action Plan is to “eliminate the use of medically important antibiotics for growth promotion in food producing animals and bring other in-feed uses of antibiotics, for treatment and disease control and prevention of disease, under veterinary oversight” by 2020.

But even if the goal is met, American livestock farmers will still face far less stringent antibiotics regulations than their Danish counterparts already follow.

Leading me inside his barn, Mr. Munck unlocked a medicine cabinet that contained a dozen or so bottles of antibiotics. He said that he usually administered antibiotics to sick animals individually, but he could add medication to feed if an entire pen became infected. He told me that he could get the antibiotics only when they were prescribed by a veterinarian, and that he had to purchase them from a pharmacy.

Danish veterinarians cannot dispense antibiotics except in emergencies, removing any financial incentives to overprescribe. The pharmacy that Mr. Munck buys his drugs from enters information about his purchases into a national database that allows the government to track exactly how much of which antibiotics each vet prescribes and each farmer uses. And any antibiotics Mr. Munck acquires have to be administered or destroyed within 35 days.

Once a year, Danish veterinarians meet with government officials to . . .

Continue reading. The article concludes:

The Danish pork industry did have some early problems with mortality among young pigs. But it overcame those by allowing piglets to nurse longer, by feeding them more nourishing rations and by receiving monthly preventive visits to farms by vets. Overall use of antibiotics in livestock has fallen by 50 percent in Denmark, even as the hog herd has increased significantly in size. Levels of resistant bacteria on farms tumbled. Mr. Munck said his animals experienced no more bacterial infections than they used to. And despite predictions to the contrary, pigs in Denmark gain weight as efficiently as they did before the introduction of the antibiotic controls.

Farmers still use antibiotics frequently, mostly to cure diarrhea and treat infected wounds, Mr. Munck said. But that’s the purpose of antibiotics. “The idea is to use as little antibiotic as possible but as much as needed,” he said.

Researchers at Iowa State University ran numbers to determine what it would cost American pork producers to put a Danish-style control system in place. The total was only $4.50 per animal, less than three cents more for a pound of pork — a pittance if it means keeping antibiotics that save human lives effective.

Written by LeisureGuy

3 April 2015 at 1:54 pm

Obama’s Plan to Save Antibiotics Has a Big Loophole

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Kaleigh Rodgers has an interesting article at Motherboard:

Antibiotics are one of the greatest medical advancements in human history. But over the last few decades our zeal for antibiotics has contributed to the growth of antibiotic-resistant superbugs. That’s why, on Friday, President Barack Obamareleased a long-awaited National Action​ Plan to respond to antibiotic resistance (AR), setting goals to be met by 2020.

The World Health Organization warned ​us all last year that if we didn’t start to seriously curb our antibiotic use, we would be heading towards “a post-antibiotic era,” in which bacterial infections from E. coli to gonorrhea would no longer be treated as they are now. Already, the Center for Disease Control and Prevention estimates 2 million illnesses and 23,000 d​eaths in the US each year are caused by drug-resistant bacteria.

The action plan is a fairly thorough document that implements a many of the necessary steps that WHO and others have recommended to slow the growth of antibiotic-resistant bugs. It calls for more judicious use of antibiotics and more rigorous, standardized testing to prevent people from taking antibiotics unnecessarily. It will also require each state to introduce AR prevention program to monitor AR bugs, and prioritize research into both drug-resistant microbes and new kinds of antibiotics.

But while attacking the problem in both the lab and doctor’s office is an important part of the strategy, many argue that the larger issue still lies on the farm. Right now, 80 percent of all of the antibiotics sold in the US are sold to livestock producers,according​ to the Natural Resources Defense Council. Farmers started using antibiotics to prevent disease in their livestock, but soon discovered the antibiotics also promoted growth. Over the past few decades, antibiotic use on farm animals has surged and is now standard practice, creating a dangerous breeding ground for antibiotic-resistant bugs in the process.

While the action plan calls for the “elimination of the use of medically-important antibiotics for growth promotion in food-producing animals,” a loophole would still allow farmers to use antibiotics to prevent disease. But since antibiotics provide both growth and disease-prevention benefits at the same time, it’s pretty hard to distinguish the two uses, leaving the door wide open for livestock producers to continue routinely using the drugs on their animals.

“This stance ignores clear evidence that the use of medically important antibiotics for routine disease prevention creates a public health risk that is identical to those posed by routine use for growth promotion,” said Steve Roach, a lawyer and senior analyst for Keeping Antibiotics Working, a nonprofit that advocates for the prevention of antibiotic resistance.

“The plan also fails to set any targets for reductions in antibiotic use in food animals,” Roach said in a press release. “All the other actions in the National Action Plan—including research, outreach to producers and veterinarians, and improved monitoring—will be wasted as long as the target to be reached falls so short of what needs to be done.”

Many chicken producers, for example, have alrea​dy decided to eliminate the use of medically-important antibiotics (i.e. ones that we use for human drugs) and chain restaurants from Chipotle to McDonald’s have committed to only sourcing chicken from these producers.

The chickens still receive antibiotics, called ionophores, that aren’t used in human medicine, so it’s more or less a win-win. The trouble is that not all chicken producers are on board and even fewer beef and pork producers have curbed their antibiotic use. Without any legal obligations to do so under the new action plan, it will continue to be an uphill battle to convince livestock producers to change common practice.

The action plan has some other, softer commitments, like . . .

Continue reading.

Written by LeisureGuy

28 March 2015 at 1:09 pm

Teaching evolution at closed minds

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Fascinating article by James Krupa in Orion magazine:

i’m often asked what I do for a living. My answer, that I am a professor at the University of Kentucky, inevitably prompts a second question: “What do you teach?” Responding to such a question should be easy and invite polite conversation, but I usually brace for a negative reaction. At least half the time the person flinches with disapproval when I answer “evolution,” and often the conversation simply terminates once the “e-word” has been spoken. Occasionally, someone will retort: “But there is no evidence for evolution.” Or insist: “It’s just a theory, so why teach it?”

At this point I should walk away, but the educator in me can’t. I generally take the bait, explaining that evolution is an established fact and the foundation of all biology. If in a feisty mood, I’ll leave them with this caution: the fewer who understand evolution, the more who will die. Sometimes, when a person is still keen to prove me wrong, I’m more than happy to share with him an avalanche of evidence demonstrating I’m not.

Some colleagues ask why I bother, as if I’m the one who’s the provocateur. I remind them that evolution is the foundation of our science, and we simply can’t shy away from explaining it. We don’t avoid using the “g-word” when talking about gravitational theory, nor do we avoid the “c-word” when talking about cell theory. So why avoid talking about evolution, let alone defending it? After all, as a biologist, the mission of advancing evolution education is the most important aspect of my job.

TO TEACH EVOLUTION at the University of Kentucky is to teach at an institution steeped in the history of defending evolution education. The first effort to pass an anti-evolution law (led by William Jennings Bryan) happened in Kentucky in 1921. It proposed making the teaching of evolution illegal. The university’s president at that time, Frank McVey, saw this bill as a threat to academic freedom. Three faculty members—William Funkhouser, a zoologist; Arthur Miller, a geologist who taught evolution; and Glanville Terrell, a philosopher—joined McVey in the battle to prevent the bill from becoming law. They put their jobs on the line. Through their efforts, the anti-evolution bill was defeated by a forty-two to forty-one vote in the state legislature. Consequently, the movement turned its attention toward Tennessee.

John Thomas Scopes was a student at the University of Kentucky then and watched the efforts of his three favorite teachers and President McVey. The reason the “Scopes Monkey Trial” occurred several years later in Dayton, Tennessee—where Scopes was a substitute teacher and volunteered to be prosecuted—was in good part due to the influence of his mentors, particularly Funkhouser. As Scopes writes in his memoir, Center of the Storm: “Teachers rather than subject matter rekindled my interest in science. Dr. Funkhouser . . . was a man without airs [who] taught zoology so flawlessly that there was no need to cram for the final examination; at the end of the term there was a thorough, fundamental grasp of the subject in bold relief in the student’s mind, where Funkhouser had left it.”

I was originally reluctant to take my job at the university when offered it twenty years ago. It required teaching three sections of non-majors biology classes, with three hundred students per section, and as many as eighteen hundred students each year. I wasn’t particularly keen on lecturing to an auditorium of students whose interest in biology was questionable given that the class was a freshman requirement.

Then I heard an interview with the renowned evolutionary biologist E. O. Wilson in which he addressed why, as a senior professor—and one of the most famous biologists in the world—he continued to teach non-majors biology at Harvard. Wilson explained that non-majors biology is the most important science class that one could teach. He felt many of the future leaders of this nation would take the class, and that this was the last chance to convey to them an appreciation for biology and science. Moved by Wilson’s words, and with the knowledge that William Funkhouser once held the job I was now contemplating, I accepted the position. The need to do well was unnerving, however, considering that if I failed as a teacher, a future Scopes might leave my class uninspired.

I realized early on that many instructors teach introductory biology classes incorrectly. Too often evolution is the last section to be taught, an autonomous unit at the end of the semester. I quickly came to the conclusion that, since evolution is the foundation upon which all biology rests, it should be taught at the beginning of a course, and as a recurring theme throughout the semester. As the renowned geneticist Theodosius Dobzhansky said: “Nothing in biology makes sense except in the light of evolution.” In other words, how else can we explain why the DNA of chimps and humans is nearly 99 percent identical, and that the blood and muscle proteins of chimps and humans are nearly identical as well? Why are these same proteins slightly less similar to gorillas and orangu­tans, while much less similar to goldfish? Only evolution can shed light on these questions: we humans are great apes; we and the other great apes (gibbons, chimps, gorillas, bonobos, and orangutans) all evolved from a common ancestor.

Soon, every topic and lecture in my class was built on an evolutionary foundation and explained from an evolutionary perspective. My basic biology for non-majors became evolution for non-majors. It didn’t take long before I started to hear from a vocal minority of students who strongly objected: “I am very offended by your lectures on evolution! Those who believe in creation are not ignorant of science! You had no right to try and force evolution on us. Your job was to teach it as a theory and not as a fact that all smart people believe in!!” And: “Evolution is not a proven fact. It should not be taught as if it is. It cannot be observed in any quantitative form and, therefore, isn’t really science.”

We live in a nation where public acceptance of evolution is the second lowest of thirty-four developed countries, just ahead of Turkey. Roughly half of Americans reject some aspect of evolution, believe the earth is less than ten thousand years old, and that humans coexisted with dinosaurs. Where I live, many believe evolution to be synonymous with atheism, and there are those who strongly feel I am teaching heresy to thousands of students. A local pastor, whom I’ve never met, wrote an article in The University Christian complaining that, not only was I teaching evolution and ignoring creationism, I was teaching it as a non-Christian, alternative religion.

There are students who enroll in my courses and already accept evolution. Although not yet particularly knowledgeable on the subject, they are eager to learn more. Then there are the students whose minds are already sealed shut to the possibility that evolution exists, but need to take my class to fulfill a college requirement. And then there are the students who have no opinion one way or the other but are open-minded. These are the students I most hope to reach by presenting them with convincing and overwhelming evidence without offending or alienating them.

Some students take offense very easily. . .

Continue reading.

And Phil Plait in Slate offers some answers to questions asked by creationists:

After writing yesterday about the now-famous/infamous debate between Bill Nye and Ken Ham, I don’t want to make this blog all creationism all the time, but indulge me this one more time, if you will. On BuzzFeed, there is a clever listicle that is a collection of 22 photos showing creationists holding up questions they have for people who “believe” in evolution.

These questions are fairly typically asked when evolution is questioned by creationists. Some are philosophical, and fun to think about, while others show a profound misunderstanding of how science works, and specifically what evolution is. I have found that most creationists who attack evolution have been taught about it by other creationists, so they really don’t understand what it is or how it works, instead they have a straw-man idea of it.

Because of this, it’s worth exploring and answering the questions presented. Some could be simply answered yes or no, but I’m all about going a bit deeper. With 22 questions I won’t go too deep, but if you have these questions yourself, or have been asked them, I hope this helps.

I’ll repeat the question below, and give my answers.

1) “Bill Nye, are you influencing the minds of children in a positive way?”

I’m not Bill, but I’d say yes, he is. More than just giving them facts to memorize, he is showing them how science works. Not only that, his clear love and enthusiasm for science is infectious, and that to me is his greatest gift.

2) “Are you scared of a Divine Creator?”

No. In fact, if there is a Judeo-Christian god, that would have fascinating implications for much of what we scientists study, and would be a rich vein to mine. Perhaps a more pertinent question is, “Are you scared there might not be a Divine Creator?” There is more room for a god in science than there is for no god in religious faith.

3) “Is it completely illogical that the Earth was created mature? i.e. trees created with rings … Adam created as an adult ….”

It might be internally consistent, even logical, but a bit of a stretch. After all, we can posit that God created the Universe last Thursday, looking exactly as it is, with all evidence pointing to it being old and your memories implanted such that you think you’re older than a mere few days. Consistent, sure, but plausible? Not really.

4) “Does not the second law of thermodynamics disprove evolution?” . . .

Continue reading.

Written by LeisureGuy

26 March 2015 at 3:26 pm

Did Neurons Evolve Twice?

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If something is a good solution, evolution tends to close in on it, and separate evolutionary paths thus reach quite similar good solutions: the eye, for example, has evolved independently 50 to 100 times. But the eye is a late-comer, evolutionarily speaking, whereas neurons are really basic—i.e., evolved very early, before much branching had been done. But, as it turns out, after some branching, so that we have different sorts of neurons. Emily Singer reports in Quanta:

When Leonid Moroz, a neuroscientist at the Whitney Laboratory for Marine Bioscience in St. Augustine, Fla., first began studying comb jellies, he was puzzled. He knew the primitive sea creatures had nerve cells — responsible, among other things, for orchestrating the darting of their tentacles and the beat of their iridescent cilia. But those neurons appeared to be invisible. The dyes that scientists typically use to stain and study those cells simply didn’t work. The comb jellies’ neural anatomy was like nothing else he had ever encountered.

After years of study, he thinks he knows why. According to traditional evolutionary biology, neurons evolved just once, hundreds of millions of years ago, likely after sea sponges branched off the evolutionary tree. But Moroz thinks it happened twice — once in ancestors of comb jellies, which split off at around the same time as sea sponges, and once in the animals that gave rise to jellyfish and all subsequent animals, including us. He cites as evidence the fact that comb jellies have a relatively alien neural system, employing different chemicals and architecture from our own. “When we look at the genome and other information, we see not only different grammar but a different alphabet,” Moroz said.

When Moroz proposed his theory, evolutionary biologists were skeptical. Neurons are the most complex cell type in existence, critics argued, capable of capturing information, making computations and executing decisions. Because they are so complicated, they are unlikely to have evolved twice.

But new support for Moroz’s idea comes from recent genetic work suggesting that comb jellies are ancient — the first group to branch off the animal family tree. If true, that would bolster the chance that they evolved neurons on their own.

The debate has generated intense interest among evolutionary biologists. Moroz’s work does not only call into question the origins of the brain and the evolutionary history of animals. It also challenges the deeply entrenched idea that evolution progresses steadily forward, building up complexity over time.

The First Split

Somewhere in the neighborhood of 540 million years ago, the ocean was poised for an explosion of animal life. The common ancestor of all animals roamed the seas, ready to diversify into the rich panoply of fauna we see today.

Scientists have long assumed that sponges were the first to branch off the main trunk of the animal family tree. They’re one of the simplest classes of animals, lacking specialized structures, such as nerves or a digestive system. Most rely on the ambient flow of water to collect food and remove waste.

Later, as is generally believed, the rest of the animal lineage split into comb jellies, also known as ctenophores (pronounced TEN-oh-fours); cnidarians (jellyfish, corals and anemones); very simple multicellular animals called placozoa; and eventually bilaterians, the branch that led to insects, humans and everything in between.

But sorting out the exact order in which the early animal branches split has been a notoriously thorny problem. We have little sense of what animals looked like so many millions of years ago because their soft bodies left little tangible evidence in rocks. “The fossil record is spotty,” said Linda Holland, an evolutionary biologist at the Scripps Institution of Oceanography at the University of California, San Diego.

To make up for our inability to see into the past, scientists use the morphology (structure) and genetics of living animals to try to reconstruct the relationships of ancient ones. But in the case of comb jellies, the study of living animals presents serious challenges.

Continue reading.

Written by LeisureGuy

25 March 2015 at 1:49 pm

Posted in Evolution, Science

Closing in on the origin of life

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God doesn’t seem to be directly involved, at least not in the common way of thinking about it. Robert Service writes in Science:

The origin of life on Earth is a set of paradoxes. In order for life to have gotten started, there must have been a genetic molecule—something like DNA or RNA—capable of passing along blueprints for making proteins, the workhorse molecules of life. But modern cells can’t copy DNA and RNA without the help of proteins themselves. To make matters more vexing, none of these molecules can do their jobs without fatty lipids, which provide the membranes that cells need to hold their contents inside. And in yet another chicken-and-egg complication, protein-based enzymes (encoded by genetic molecules) are needed to synthesize lipids.

Now, researchers say they may have solved these paradoxes. Chemists report today that a pair of simple compounds, which would have been abundant on early Earth, can give rise to a network of simple reactions that produce the three major classes of biomolecules—nucleic acids, amino acids, and lipids—needed for the earliest form of life to get its start. Although the new work does not prove that this is how life started, it may eventually help explain one of the deepest mysteries in modern science.

“This is a very important paper,” says Jack Szostak, a molecular biologist and origin-of-life researcher at Massachusetts General Hospital in Boston, who was not affiliated with the current research. “It proposes for the first time a scenario by which almost all of the essential building blocks for life could be assembled in one geological setting.”

Scientists have long touted their own favorite scenarios for which set of biomolecules formed first. “RNA World” proponents, for example suggest . . .

Continue reading.

The exciting thing is that if it’s the result of a natural process, then life must be present across our galaxy and others. Intelligent life, of course, is another story, and is rare even on earth.

Written by LeisureGuy

18 March 2015 at 4:58 pm

Posted in Evolution, Science

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