Chemicals in primate teeth reveal transition to solid food.
The changing ratios of calcium and barium in the teeth of modern humans and macaques chronicle the transition from mother’s milk to solid food — and may provide clues about the weaning habits of Neanderthals, a new study suggests.
Life on Earth is made of left-handed amino acids (L-amino acids). The question of why organisms on Earth consist of L-amino acids instead of D-amino acids or consist of D-sugar instead of L-sugar is still an unresolved riddle. Recent research into star and planet formation throws new light on this question.
A research team with Jungmi Kwon (GUAS/NAOJ) has performed deep imaging linear and circular polarimetry of the ‘Cat’s Paw Nebula’ (NGC 6334), located in the constellation Scorpius, and detected high degrees of circular polarization (CP) — as much as 22% in NGC 6334. The detected CP degree is the highest ever observed.
Origin Of Life: New Study Spotlights Not Chemistry But How Living Things Store, Process Information
Scientists trying to unravel the mystery of life’s origins have been looking at it the wrong way, a new study argues.
Instead of trying to recreate the chemical building blocks that gave rise to life 3.7 billion years ago, scientists should use key differences in the way that living creatures store and process information, suggests new research detailed today (Dec. 11) in the Journal of the Royal Society Interface.“In trying to explain how life came to exist, people have been fixated on a problem of chemistry, that bringing life into being is like baking a cake, that we have a set of ingredients and instructions to follow,” said study co-author Paul Davies, a theoretical physicist and astrobiologist at Arizona State University. “That approach is failing to capture the essence of what life is about.”
Living systems are uniquely characterized by two-way flows of information, both from the bottom up and the top down in terms of complexity, the scientists write in the article. For instance, bottom up would move from molecules to cells to whole creatures, while top down would flow the opposite way. The new perspective on life may reframe the way that scientists try to uncover the origin of life and hunt for strange new life forms on other planets.
“Right now, we’re focusing on searching for life that’s identical to us, with the same molecules,” said Chris McKay, an astrobiologist at the NASA Ames Research Center who was not involved in the study. “Their approach potentially lays down a framework that allows us to consider other classes of organic molecules that could be the basis of life.”
Chemical approach
For decades, scientists have tried to recreate the primordial events that gave rise to life on the planet. In the famous Miller-Urey experiments reported in 1953, scientists electrically charged a primordial soup of chemicals that mimicked the chemical makeup of the planet’s early oceans and found that several simple amino acids, the most primitive building blocks of life, formed as a result.But since then, scientists aren’t much further along in understanding how simple amino acids could have eventually morphed into simple, and then complex, living beings.
Part of the problem is that there isn’t really a good definition of what life is, said Sara Walker, study co-author and an astrobiologist at Arizona State University.
“Usually the way we identify life on Earth is always by having DNA present in the organism,” Walker told LiveScience. “We don’t have a rigorous mathematical way of identifying it.”
Using a chemical definition of life — for instance, requiring DNA — may limit the hunt for extraterrestrial life, and it also may wrongly include nonliving systems, for instance, a petri dish full of self-replicating DNA, she said.
Information processing
Walker’s team created a simple mathematical model to capture the transition from a nonliving to a living-breathing being. According to the researchers, all living things have one property that inanimate objects don’t: Information flows in two directions.For instance, when a person touches a hot stove, the molecules in his hand sense heat, transmit that information to the brain, and the brain then tells the molecules of the hand to move. Such two-way information flow governs the behavior of simple and complex life forms alike, from the tiniest bacteria to the giant humpback whale. By contrast, if you put a cookie on the stove, the heat may burn the cookie, but the treat won’t do anything to respond.
Another hallmark of living beings is that they have different physical locations for storing and reading information. For instance, the alphabet of letters in DNA carries the instructions for life, but another part of the cell, called the ribosome, must translate those instructions into actions inside the cell, Davies told LiveScience.
(By this definition, computers, which store data on a hard drive and read it off using a central processing unit, would have the hallmarks of life, although that doesn’t mean they are alive per se, Walker said.)
The new model is still in its infancy and doesn’t yet point to new molecules that could have spawned life on other planets. But it lays out the behavior needed for a system needs to be considered living, Walker said.
“This is a manifesto,” said Davies. “It’s a call to arms and a way to say we’ve got to reorient and redefine the subject and look at it in a different way.”
ScienceDaily (Nov. 26, 2012) — The question of how life began on a molecular level has been a longstanding problem in science. However, recent mathematical research sheds light on a possible mechanism by which life may have gotten a foothold in the chemical soup that existed on the early Earth.
In early 2012, organic chemists at the University of York made a significant advance towards establishing the origin of the carbohydrates (sugars) that form the building blocks of life. A team led by Dr Paul Clarke in the Department of Chemistry at York re-created a process which could have occurred in the prebiotic world.
“There are a lot of fundamental questions about the origins of life and many people think they are questions about biology. But for life to have evolved, you have to have a moment when non-living things become living — everything up to that point is chemistry,” Clarke said.
“We are trying to understand the chemical origins of life. One of the interesting questions is where carbohydrates come from because they are the building blocks of DNA and RNA. What we have achieved is the first step on that pathway to show how simple sugars –threose and erythrose—originated. We generated these sugars from a very simple set of materials that most scientists believe were around at the time that life began.”
All biological molecules have an ability to exist as left-handed forms or right-handed forms. All sugars in biology are made up of the right-handed form of molecules and yet all the amino acids that make up the peptides and proteins are made up of the left-handed form.
The researchers found using simple left-handed amino acids to catalyse the formation of sugars resulted in the production of predominately right-handed form of sugars. It could explain how carbohydrates originated and why the right-handed form dominates in nature.
ScienceDaily (Apr. 19, 2012) — Living systems owe their existence to a pair of information-carrying molecules: DNA and RNA. These fundamental chemical forms possess two features essential for life: they display heredity — meaning they can encode and pass on genetic information, and they can adapt over time, through processes of Darwinian evolution.
A long-debated question is whether heredity and evolution could be performed by molecules other than DNA and RNA.
ScienceDaily (Mar. 12, 2012) — In the beginning — of the ribosome, the cell’s protein-building workbench — there were ribonucleic acids, the molecules we call RNA that today perform a host of vital functions in cells. And according to a new analysis, even before the ribosome’s many working parts were recruited for protein synthesis, proteins also were on the scene and interacting with RNA. This finding challenges a long-held hypothesis about the early evolution of life.
Primordial soup
Life on Earth began more than 3 billion years ago, evolving from the most basic of microbes into a dazzling array of complexity over time. But how did the first organisms on the only known home to life in the universe develop from the primordial soup? Here are science’s theories on the origins of life on Earth.
Electric Spark
Electric sparks can generate amino acids and sugars from an atmosphere loaded with water, methane, ammonia and hydrogen, as was shown in the famous Miller-Urey experiment reported in 1953, suggesting that lightning might have helped create the key building blocks of life on Earth in its early days. Over millions of years, larger and more complex molecules could form. Although research since then has revealed the early atmosphere of Earth was actually hydrogen-poor, scientists have suggested that volcanic clouds in the early atmosphere might have held methane, ammonia and hydrogen and been filled with lightning as well.
Community Clay
The first molecules of life might have met on clay, according to an idea elaborated by organic chemist Alexander Graham Cairns-Smith at the University of Glasgow in Scotland. These surfaces might not only have concentrated these organic compounds together, but also helped organize them into patterns much like our genes do now. The main role of DNA is to store information on how other molecules should be arranged. Genetic sequences in DNA are essentially instructions on how amino acids should be arranged in proteins. Cairns-Smith suggests that mineral crystals in clay could have arranged organic molecules into organized patterns. After a while, organic molecules took over this job and organized themselves. Deep-Sea Vents The deep-sea vent theory suggests that life may have begun at submarine hydrothermal vents, spewing key hydrogen-rich molecules. Their rocky nooks could then have concentrated these molecules together and provided mineral catalysts for critical reactions. Even now, these vents, rich in chemical and thermal energy, sustain vibrant ecosystems. Chilly Start Ice might have covered the oceans 3 billion years ago, as the sun was about a third less luminous than it is now. This layer of ice, possibly hundreds of feet thick, might have protected fragile organic compounds in the water below from ultraviolet light and destruction from cosmic impacts. The cold might have also helped these molecules to survive longer, allowing key reactions to happen. RNA World
Nowadays DNA needs proteins in order to form, and proteins require DNA to form, so how could these have formed without each other? The answer may be RNA, which can store information like DNA, serve as an enzyme like proteins, and help create both DNA and proteins. Later DNA and proteins succeeded this “RNA world,” because they are more efficient. RNA still exists and performs several functions in organisms, including acting as an on-off switch for some genes. The question still remains how RNA got here in the first place. And while some scientists think the molecule could have spontaneously arisen on Earth, others say that was very unlikely to have happened. Other nucleic acids other than RNA have been suggested as well, such as the more esoteric PNA or TNA. Simple Beginnings Instead of developing from complex molecules such as RNA, life might have begun with smaller molecules interacting with each other in cycles of reactions. These might have been contained in simple capsules akin to cell membranes, and over time more complex molecules that performed these reactions better than the smaller ones could have evolved, scenarios dubbed “metabolism-first” models, as opposed to the “gene-first” model of the “RNA world” hypothesis. Panspermia Perhaps life did not begin on Earth at all, but was brought here from elsewhere in space, a notion known as panspermia. For instance, rocks regularly get blasted off Mars by cosmic impacts, and a number of Martian meteorites have been found on Earth that some researchers have controversially suggested brought microbes over here, potentially making us all Martians originally. Other scientists have even suggested that life might have hitchhiked on comets from other star systems. However, even if this concept were true, the question of how life began on Earth would then only change to how life began elsewhere in space. Image Credits: NASA/JPL, stock.xchng, Chemistry, MARUM, Eric Rignot & NASA JPL, © Yunxiang987 | Dreamstime.com, © Mark Rasmussen | Dreamstime.com
Saturn’s Titan: Clues to the Origins of Life in the Universe?
“Titan is just covered in carbon-bearing material — it’s a giant factory of organic chemicals,” according to Ralph Lorenz of Johns Hopkins University Applied Physics Laboratory. “We are carbon-based life, and understanding how far along the chain of complexity towards life that chemistry can go in an environment like Titan will be important in understanding the origins of life throughout the universe.”
Continue reading “Saturn’s Titan: Clues to the Origins of Life in the Universe?” »
Based on some fundamental characteristics of cellular proteins, a team of scientists speculates that the last common ancestor of life on Earth got its start in the planet’s natural hot tubs.
Earth started as a violent place, its surface churned by continuous volcanic eruptions and cloaked in an atmosphere that would have been poisonous to today’s life-forms. Furthermore, the thin primeval atmosphere may have provided only scant protection from the young sun’s harsh ultraviolet glare. Given these inhospitable conditions, scientists have long wondered: How did the first cells come to be nearly four billion years ago?
