More than 150 years ago, Darwin proposed the theory of universal common ancestry (UCA), linking all forms of life by a shared genetic heritage from single-celled microorganisms to humans. Until now, the theory that makes ladybugs, oak trees, champagne yeast and humans distant relatives has remained beyond the scope of a formal test. This week, a Brandeis biochemist reports in Nature the results of the first large scale, quantitative test of the famous theory that underpins modern evolutionary biology.
The results of the study confirm that Darwin had it right all along. In his 1859 book, On the Origin of Species, the British naturalist proposed that, "all the organic beings which have ever lived on this earth have descended from some one primordial form." Over the last century and a half, qualitative evidence for this theory has steadily grown, in the numerous, surprising transitional forms found in the fossil record, for example, and in the identification of sweeping fundamental biological similarities at the molecular level.
Still, rumblings among some evolutionary biologists have recently emerged questioning whether the evolutionary relationships among living organisms are best described by a single "family tree" or rather by multiple, interconnected trees—a "web of life." Recent molecular evidence indicates that primordial life may have undergone rampant horizontal gene transfer, which occurs frequently today when single-celled organisms swap genes using mechanisms other than usual organismal reproduction. In that case, some scientists argue, early evolutionary relationships were web-like, making it possible that life sprang up independently from many ancestors.
According to biochemist Douglas Theobald, it doesn't really matter. "Let's say life originated independently multiple times, which UCA allows is possible," said Theobald. "If so, the theory holds that a bottleneck occurred in evolution, with descendants of only one of the independent origins surviving until the present. Alternatively, separate populations could have merged, by exchanging enough genes over time to become a single species that eventually was ancestral to us all. Either way, all of life would still be genetically related."
Harnessing powerful computational tools and applying Bayesian statistics, Theobald found that the evidence overwhelmingly supports UCA, regardless of horizontal gene transfer or multiple origins of life. Theobald said UCA is millions of times more probable than any theory of multiple independent ancestries.
"There have been major advances in biology over the last decade, with our ability to test Darwin's theory in a way never before possible," said Theobald. "The number of genetic sequences of individual organisms doubles every three years, and our computational power is much stronger now than it was even a few years ago."
While other scientists have previously examined common ancestry more narrowly, for example, among only vertebrates, Theobald is the first to formally test Darwin's theory across all three domains of life. The three domains include diverse life forms such as the Eukarya (organisms, including humans, yeast, and plants, whose cells have a DNA-containing nucleus) as well as Bacteria and Archaea (two distinct groups of unicellular microorganisms whose DNA floats around in the cell instead of in a nucleus).
Theobald studied a set of 23 universally conserved, essential proteins found in all known organisms. He chose to study four representative organisms from each of the three domains of life. For example, he researched the genetic links found among these proteins in archaeal microorganisms that produce marsh gas and methane in cows and the human gut; in fruit flies, humans, round worms, and baker's yeast; and in bacteria like E. coli and the pathogen that causes tuberculosis.
Theobald's study rests on several simple assumptions about how the diversity of modern proteins arose. First, he assumed that genetic copies of a protein can be multiplied during reproduction, such as when one parent gives a copy of one of their genes to several of their children. Second, he assumed that a process of replication and mutation over the eons may modify these proteins from their ancestral versions. These two factors, then, should have created the differences in the modern versions of these proteins we see throughout life today. Lastly, he assumed that genetic changes in one species don't affect mutations in another species—for example, genetic mutations in kangaroos don't affect those in humans.
What Theobald did not assume, however, was how far back these processes go in linking organisms genealogically. It is clear, say, that these processes are able to link the shared proteins found in all humans to each other genetically. But do the processes in these assumptions link humans to other animals? Do these processes link animals to other eukaryotes? Do these processes link eukaryotes to the other domains of life, bacteria and archaea? The answer to each of these questions turns out to be a resounding yes.
Just what did this universal common ancestor look like and where did it live? Theobald's study doesn't answer this question. Nevertheless, he speculated, "to us, it would most likely look like some sort of froth, perhaps living at the edge of the ocean, or deep in the ocean on a geothermal vent. At the molecular level, I'm sure it would have looked as complex and beautiful as modern life."
The research, which involves regenerating the sensitive hair cells that turn sound vibrations into nerve signals, was described as "really exciting" and could benefit millions of people.
Humans are born with 30,000 hair cells in each ear.
When the cells are lost or damaged – possibly due to exposure to excessive loud noise or injury – it can lead to permanent hearing loss or tinnitus (ringing in the ears).
Damage to hair cells may also affect balance, causing symptoms of vertigo and dizziness.
Regenerating the sensory hair cells of the inner ear has been the holy grail of deafness research.
The new breakthrough is the culmination of 10 years' work by scientists in California.
A team led by Professor Stefan Heller, from Stanford University School of Medicine, succeeded in programming mouse stem cells to develop into immature hair cells.
Viewed under an electron microscope, they were seen to have bundled structures reminiscent of the hairlike tufts of "stereocilia" that give the cells their name.
"They really looked like they were more or less taken out of the ear," said Prof Heller.
Most importantly, tests showed that the cells responded to being moved the way hair cells do, by converting mechanical signals into electrical ones.
Experts hope the cells, which could be made in large numbers from multiplying stem cells, will provide an invaluable research tool for studying the molecular basis of hearing and deafness.
Further down the line, they may also help scientists find a way of coaxing a patient's hair cells to renew themselves.
The research is already being taken forward by scientists supported by the Royal National Institute for Deaf people (RNID).
Dr Ralph Holme, head of biomedical research at the charity, said: "The possibility that stem cells could one day be used to restore hearing is really exciting and could benefit millions.
"RNID-funded research has shown that human stem cells can also give rise to hairlike cells, an important step forward in developing a clinically relevant therapy.
"We are now supporting research to investigate whether hearing can be restored using these cells in preclinical models of deafness and to find ways of scaling up the production of safe, clinical-grade cells."
David Corey, Professor of Neurobiology at Harvard University in Boston, said: "This gives us real hope that there might be some kind of therapy for regenerating hair cells. It could take a decade or more, but it's a possibility."
The Stanford research, the first to create functional inner-ear cells, is reported in the journal Cell.
Prof Heller's team used both mouse embryonic stem cells and artificially "induced" stem cells made by reprogramming ordinary skin cells.
Embryonic stem cells, removed from early-stage embryos, are "mother" cells with the ability to transform into virtually any kind of tissue in the body. Induced stem cells have similar "pluripotent" properties.
In both cases, the cells were exposed to special cocktails of chemicals that caused them to pass through a range of development phases normally seen in the womb.
"We looked at how the ear develops in an embryo, at the developmental steps, and mimicked these steps in a culture dish," said Prof Heller.
"These cells have a very intriguing structure. They look like they have hair tufts of stereocilia."
Inside the fluid-filled inner ear, hair cells respond to currents set up by the vibrating ear drum via a set of tiny bones.
The movements trigger electrical nerve impulses from the cells that are transmitted to the brain.
A similar property was observed in the lab-manufactured cells.
DuPont has excelled where no man has before—demonstrating the first OLED panels to be printed, and in under two minutes no less. Using a Dainippon Screen multi-nozzle printer, they successfully created a 50-inch display.
This is something they've been talking about for years now, so it's pleasing to see DuPont has finally managed to achieve their (rather lofty) goals. The OLED panels have a purported lifetime of 15 years, and will help bring the cost right down if they're able to be created in the time it takes to boil the kettle.
DuPont teamed up with Dainippon Screen, whose printers can squeeze out active molecules within the ink, layering them up between 12 to 15 layers—taking just a second to drop 4 - 5m of ink down. Pretty amazing stuff, and great news for anyone who's ever fallen in love with Sony or LG's OLED panels. [Technology-Review via OLED-Display]
At extremely low temperatures atoms can aggregate into so-called Bose Einstein condensates forming coherent laser-like matter waves. Due to interactions between the atoms fundamental quantum dynamics emerge and give rise to periodic collapses and revivals of the matter wave field.
A group of scientists led by Professor Immanuel Bloch (Max Planck Institute of Quantum Optics in Garching, Germany) has now succeeded to take a glance 'behind the scenes' of atomic interactions revealing the complex structure of these quantum dynamics. By generating thousands of miniature BECs ordered in an optical lattice the researchers were able to observe a large number of collapse and revival cycles over long periods of time. The experimental results imply that the atoms do not only interact pairwise - as typically assumed - but also perform exotic collisions involving three, four or more atoms at the same time. On the one hand, these results have fundamental importance for the understanding of quantum many-body systems. On the other hand, they pave the way for the generation of new exotic states of matter, based on such multi-body interactions.
The experiment starts by cooling a dilute cloud of hundreds of thousands of atoms to temperatures close to absolute zero, approximately -273 degrees Celsius. At these temperatures the atoms form a so-called Bose-Einstein condensate (BEC), a quantum phase in which all particles occupy the same quantum state. Now an optical lattice is superimposed on the BEC: This is a kind of artificial crystal made of light with periodically arranged bright and dark areas, generated by the superposition of standing laser light waves from different directions. This lattice can be viewed as an 'egg carton' on which the atoms are distributed. Whereas in a real egg carton each site is either occupied by a single egg or no egg, the number of atoms sitting at each lattice site is determined by the laws of quantum mechanics: Depending on the lattice height (i.e. the intensity of the laser beam) the single lattice sites can be occupied by zero, one, two, three and more atoms at the same time.
Scientists say the revolutionary 'STAIR' (St Andrews Air) battery could now pave the way for a new generation of electric cars, laptops and mobile phones.
The cells are charged in a traditional way but as power is used or 'discharged' an open mesh section of battery draws in oxygen from the surrounding air.
This oxygen reacts with a porous carbon component inside the battery, which creates more energy and helps to continually 'charge' the cell as it is being discharged.
By replacing the traditional chemical constituent, lithium cobalt oxide, with porous carbon and oxygen drawn from the air, the cell is much lighter than current batteries.
And as the cycle of air helps re-charge the battery as it is used, it has a greater storage capacity than other similar-sized cells and can emit power up to 10 times longer.
Professor Peter Bruce of the Chemistry Department at the University of St Andrews, said: "The benefits are it's much smaller and lighter so better for transporting small applications.
"The size is also crucial for anyone trying to develop electric cars as they want to keep weight down as much as possible.
"Storage is also important in the development of green power. You need to store electricity because wind and solar power is intermittent."
Positronium is a short-lived system in which an electron and its anti-particle are bound together. In 2007, physicists at the University of California, Riverside created molecular positronium, a brand-new substance, in the laboratory. Now they have succeeded in isolating for the first time a sample of spin polarized positronium atoms.
Study results appear this week in the journal Physical Review Letters.
Spin is a fundamental and intrinsic property of an electron, and refers to the electron's angular momentum. Spin polarized atoms are atoms that are all in the same spin state. A collection of spin polarized positronium atoms is needed to make a special form of matter, called the Bose-Einstein condensate (BEC). The BEC, predicted in 1924 and created in 1995, allows scientists to study atoms in a unique manner.
"We achieved our result by increasing the density of the positronium atoms in our lab experiment," said David Cassidy, the lead author of the research paper and an assistant researcher working in the laboratory of Allen Mills, a professor of physics. "At such a high density, positronium atoms get annihilated simply by interacting with each other. But it turns out that not all the positronium atoms get annihilated under these conditions."
Cassidy explained that positronium atoms come in two types - say, an up type and a down type. The positronium atoms are only annihilated when an up type meets a down type. Two atoms of the same type do not affect each other.
"So if you have 50 percent ups and 50 percent downs and you squeeze them all together they will totally annihilate and turn into gamma rays," he said. "But if you have, for example, about 66 percent ups and 33 percent downs, then only half of the ups will be destroyed. You will get a load of gamma rays - but in the end you will be left with only one type of atom - in this case, up atoms.
"This is an important development for making the BEC," Cassidy said, "because you have effectively purified your sample of positronium. And you need a pure collection of spin aligned atoms to make the BEC."
When atoms are in the BEC state, they are essentially stopped (or they move extremely slowly), facilitating their study. Non-BEC atoms on the other hand whiz around at very high speeds, making them harder to study.
"There are fundamental processes that can be looked at in new ways when you have matter in the BEC state," Mills said. "Having Bose-condensed atoms makes it easier to probe the way they interact under certain conditions. Moreover, to have motionless positronium atoms is an important aspect for making something called a gamma ray laser, which could have military and numerous scientific applications."
According to Mills and Cassidy, the new research could lead also to the production of fusion power, which is power generated by nuclear fusion reactions.
"The eventual production of a positronium condensate could help us understand why the universe is made of matter and not antimatter or just pure energy," Cassidy said. "It could also one day help us measure the gravitational interaction of antimatter with matter. At present, nobody knows for sure if antimatter falls up or down."
Could our universe be located within the interior of a wormhole which itself is part of a black hole that lies within a much larger universe?
Such a scenario in which the universe is born from inside a wormhole (also called an Einstein-Rosen Bridge) is suggested in a paper from Indiana University theoretical physicist Nikodem Poplawski in Physics Letters B. The final version of the paper was available online March 29 and will be published in the journal edition April 12.
Poplawski takes advantage of the Euclidean-based coordinate system called isotropic coordinates to describe the gravitational field of a black hole and to model the radial geodesic motion of a massive particle into a black hole.
Imagine a 120-year-old living like today’s 50 year-olds. Possible? Yes, according to the scientists in Robert Kane Pappas’ new film, To Age or Not to Age