Archive for May, 2009

Argentavis, the largest flying bird, was a master glider

By Ed Yong | May 31, 2009 8:06 am


Blogging on Peer-Reviewed ResearchSix million years ago, the skies of Argentina were home to fearsome predator – Argentavis magnificens, the largest bird to ever take to the air. It weighed in at 70kg and had a wingspan of 7m, about the same size as a Cessna 152 light aircraft.

An artist rendering of ArgentavisArgentavis was a member of an extinct group of predatory birds understandably called the teratorns – ‘monster birds’. They are related to storks and New World vultures such as turkey vultures and condors. But Argentavis completely dwarfed even the massive Andean condor, weighing six times more and with a wingspan over twice as long (in the picture below, its silhouette is placed next to a bald eagle for scale).

There is no question that Argentavis flew. It has all the characteristics of modern flyers including light, hollow bones and strong, sturdy wings. It’s how it flew that palaeontologists have puzzled over, given its massive size in relation to modern birds. For a start, how did it get its large bulk off the ground in the first place? The heaviest living flier, the Great Kori Bustard, is over three times lighter than Argentavis, and even it can only take off after arduously ‘taxiing’ like a airplane.

Sankar Chatterjee from the Museum of Texas Tech University decided to model the giant’s flying style by running simulations with known fossils. He found that Argentavis simply couldn’t have generated enough lift from a running-take-off. It needed height to get airborne, but it could manage with surprisingly little. Even a gentle down-slope of 10° and a light headwind would have given it enough extra power to avoid an embarrassing crash. Albatrosses and hang-glider pilots use the same technique today.

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Scientists "humanise" Foxp2 gene in mice to probe origins of human language

By Ed Yong | May 29, 2009 8:30 am

Blogging on Peer-Reviewed ResearchWhen Walt Disney created Mickey Mouse in 1928, he understood the draw that anthropomorphic mice would have. But even Walt’s imagination might have struggled to foresee the events that have just taken place in a German genetics laboratory. There, a group of scientists led by Wolfgang Enard have “humanising” a gene in mice to study its potential relevance for human evolution.

Mickeymouse.jpgThe gene in question is the fascinating FOXP2, which I have written extensively about before, particularly in a feature for New Scientist. FOXP2 was initially identified as the gene behind an inherited disorder that affected language and grammar skills. Subsequently hailed as a “language gene”, it proved to be anything but. The gene, and its encoded protein, is incredibly conserved among animals, even among those without sophisticated communication skills. The chimp version differs from our own by just two amino acids; the mouse adds a single change on top of that. 

The two amino acids that have cropped up since our split from chimps are unique to us and there’s plenty of evidence that they’re the result of intense natural selection. There has always been the tantalising possibility that these changes were crucial for the evolution of our speech and language skills but until now, no one really understood their purpose. No human has ever been found with mutations at these crucial positions. Obviously, genetically manipulating humans or chimps is out of the question, but the fact that the mouse version is so similar gave Enard a unique opportunity.

He tweaked the mouse Foxp2 so that it produced a protein with the two human-specific amino acids. The resulting mice couldn’t speak like their cartoon equals, but their calls were subtly altered, their central nervous system developed in different ways, and they showed changes in parts of the brain where FOXP2 is usually expressed (switched on) in humans. Simon Fisher, who first discovered the important role of FOXP2 and contributed to the study, says, “This shows, for the first time, that the [human-specific] amino-acid changes do indeed have functional effects, and that they are particularly relevant to the brain.”

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CATEGORIZED UNDER: Evolution, Genetics, Language
MORE ABOUT: foxp2, gene, humanise, Language, mice

The bacterial zoo living on your skin

By Ed Yong | May 28, 2009 2:00 pm

It’s a diverse melting-pot of different groups, with hundreds of different cultures living together in harmony, many sticking to their own preferred areas. No, not London, New York or any other cosmopolitan city; I’m talking about your skin. It may all look the same to you, but to the bacteria living on it, it’s an entire realm of diverse habitats.

From a microscopic perspective, the hairy, moist surface of your armpits is worlds apart from the smooth, dry skin of your forearms. Even though they are separated by mere inches, these patches of skin are as different to their microscopic residents as rainforests and deserts are to us.

The true diversity of the bacteria on our bodies has just been revealed by Elizabeth Grice from the National Human Genome Research Institute, who has done a thorough survey of our “skin microbiome”. She recruited 10 healthy volunteers and took swabs from 20 distinct patches of their skin, all areas that are often afflicted by skin disorders. These areas represent a broad range of habitats from the oily lakes of the eyebrows, nose, inner ear and upper chest, to the moist jungles of the groin, nose, armpit and navel, to dry deserts of the forearms and palm.

By sequencing the distinctive 16S rRNA gene of over 112,000 bacterial samples, Grice catalogued a much broader menagerie of microbes than expected, with representatives from 19 different phyla and 205 different genera. Previous attempts at doing this have been biased towards species that grow easily in laboratory conditions such as Staphylococcus, but Grice’s more thorough approach revealed a surprising degree of diversity. It also showed that bacteria from a specific body part have more in common than those from a specific person. Your butt microbes have more in common with mine than they do with your elbow microbes.

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The peril of positive thinking – why positive messages hurt people with low self-esteem

By Ed Yong | May 27, 2009 8:30 am

Blogging on Peer-Reviewed ResearchWhen the going gets tough, thousands of people try to boost their failing self-esteem by repeating positive statements to themselves. Encouraged by magazine columnists, self-help books and talk-show hosts, people prepare for challenges by chanting positive mantras like “I am a strong, powerful person,” and, “Nothing can stop me from achieving my dreams.” This approach has been championed at least as far back as Norman Vincent Peale’s infamous book The Power of Positive Thinking, published in 1952.

But a new study suggests that despite its popularity, this particular brand of self-help may backfire badly.  Ironically, it seems to be people with low self-esteem, who are most likely to rely on such statements, who are most likely to feel worse because of them. Joanne Wood from the University of Waterloo found that people with low self-esteem who repeated “I’m a lovable person” to themselves felt worse than people who did neither.

The effect may be counter-intuitive, but the theory behind it is very straightforward. Everyone has a range of ideas they are prepared to accept. Messages that lie within this boundary are more persuasive than those that fall outside it – those meet the greatest resistance and can even lead to people holding onto their original position more strongly.

If a person with low self-esteem says something that’s positive about themselves but is well beyond what they’ll actually believe, their immediate reaction is to dismiss the claim and draw even further into their own self-loathing convictions. The positive statements could even act as reminders of failure, highlighting whatever gulf someone sees between reality and the standard they set for themselves. In short, someone could repeat “I’m a lovable person” but they’d really be thinking “I’m actually not” or  “I’m not as lovable as I should be.” Statements that contradict a person’s self-image, no matter how rallying in intention, are likely to boomerang.

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The infofuse – encoding messages using colourful fire

By Ed Yong | May 26, 2009 8:30 am

Blogging on Peer-Reviewed ResearchFor many of us, the most memorable bits of school chemistry classes were lessons where we ignited metal salts over a Bunsen burner to produce brightly coloured flames, from the lilac of potassium to the distinctive red of lithium. Now a group of chemists from Harvard University have found a way of using these colourful flames to transmit coded information.

Working in the lab of legendary chemist George Whitesides, Samuel Thomas III has developed the ‘infofuse’, a strip of flammable paper patterned with metal salts. As the strip burns, the metals change the colour of the flames, creating coded pulses of light that can be used to send messages. It’s a vibrant, visual equivalent of Morse code and as a test-run, they used their infofuses to transmit the message, “LOOK MOM NO ELECTRICITY”.

Thomas sees the infofuses as the first step toward a lightweight, self-powered form of communication that doesn’t involve any electronics to store or transmit information. “We’re interested in the intersection of information and chemistry,” says Thomas, who dubs his work as ‘infochemistry’. “Cells communicate using chemical signals, and we are interested in bridging the gap between that sort of chemical communication and the digital communication that our technological infrastructure is built on.”

DNA is the biological epitome of this concept. Through a chain of molecules, it encodes instructions for building proteins that is then transmitted in the form of RNA and translated by enzymes. Outside the realm of biology, similar systems don’t exist. You could think of signal flares, smoke signals of even litmus tests as ways of transmitting information through chemistry, albeit simple and slow ones. The infofuse is more sophisticated.

It is made of a highly flammable material called nitrocellulose or ‘flash paper’. It burns with a 1,000C flame that moves along the paper at a constant speed, producing very little smoke and leaving no ash. Codes are written on the paper using small spots of metal ions dotted along the fuse strip using either a small pipette or an inkjet printer. As the strip burns, the wavelengths and order of the flames carry messages.


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Bleached corals recover in the wake of hurricanes

By Ed Yong | May 25, 2009 12:22 pm


Blogging on Peer-Reviewed ResearchIn 2005, corals in the large reef off the coast of Florida were saved by four hurricanes. Tropical storms seem to be unlikely heroes for any living thing. Indeed, coral reefs directly in the way of a hurricane, or even up to 90km from its centre, suffer serious physical damage. But Derek Manzello from the National Oceanic and Atmospheric Administation has found that corals just outside the storm’s path reap an unexpected benefit.

Hurricanes can reverse coral bleaching by cooling surrounding waterHurricanes can significantly cool large stretches of ocean as they pass overhead, by drawing up cooler water from the sea floor. And this cooling effect, sometimes as much as 5°C, provides corals with valuable respite from the effects of climate change.

As the globe warms, the temperature of its oceans rises and that causes serious problems for corals. Their wellbeing depends on a group of algae called zooxanthellae that live among their limestone homes and provide them with energy from photosynthesis. At high temperatures, the corals eject the majority of these algae, leaving them colourless and starving.

These ‘bleached’ corals are living on borrowed time. If conditions don’t improve, they fail to recover their algae and eventually die. But if the water starts to cool again, they bounce back, and Manzello found that hurricanes can help them to do this.

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MORE ABOUT: Corals, hurricanes

Sunday links

By Ed Yong | May 24, 2009 5:20 pm

The big story this week was obviously the unveiling of Ida (Darwinius maxillae), the fossil that would CHANGE EVERYTHING!!!!11!11!!!!1! Everyone’s pitched in with their take on the fossil, but if you had to pick any sources to watch, choose Laelaps and the Loom. Brian produced the first detailed analysis of the paper, while Carl’s kept tabs on the story’s timeline, including the amusing furore over whether Darwinius‘s name was actually rightly assigned.

Steven Novella at Neurologica gives a great account of the pseudoscience of spontaneous human combustion.

Miriam from the Oyster’s Garter reveals the dark side of dolphin life, including violence, rape and infanticide. For old Ecco players, you can do all of those things by pressing Up Down Left A B B A Right.

Carl Zimmer looked at a fascinating study that tackles nothing less than the origin of life. It looked at how one of the constituents of RNA, one of the key molecules of life, could have arisen from the chemical soup of primordial Earth.

Eric Michael Johnson of the Primate Diaries brings us the fourth edition of new carnival Scientia Pro Publica, a collection of blog posts explaining science to the lay public. Quite a few of them are far too technical, but there are some great science writing gems in there.  

This year’s Illusion of the Year winners have been announced and are ready to screw with your mind.

Some obscure blogger called PZ Myers draws your attention to the flying squid, which can glide over the ocean surface. The minute they learn to wield cutlasses is the minute we’re all doomed.

Frank the SciencePunk unveils tiny cities made of crystal.

Vaughan at Mind Hacks has two great posts on the popular myth that dopamine equals pleasure and the newspaper headlines which claimed that emotionally intelligent women have more orgasms.  

ScienceBlogs is witnessing an exodus of Johns, as two of our finest – Wilkins and Lynch – have migrated their evolving thoughts and stranger fruits to WordPress. Go follow them and poke them with sticks.

Those marine perverts at Deep Sea News have been having an entire week devoted to deviant sexual practices of the deep. Pop on some Barry White and learn about how wet things are getting wetter. I’ll stop now.


Altruistic chimpanzees clearly help each other out

By Ed Yong | May 23, 2009 12:00 pm


Blogging on Peer-Reviewed ResearchTwo years ago, a group of Ugandan chimps provided a blow to the idea that humans are the only animals that truly behave selflessly to one another. These chimps showed clear signs of true selflessness, helping both human handlers and other unrelated chimps with no desire for reward.

The question of why we help each other, instead of looking out for ourselves, is one of the most compelling in modern biology. Evolutionary and game theory alike predict that selfish behaviour should be the rule with altruism the exception, and animal experiments have largely supported this idea. Nature, ‘red in tooth and claw’, is painted as a fierce competition between selfish individuals and their even more selfish genes. In this stark landscape, true altruism is apparently a rare quality and some scientists believe that it’s one that only we humans possess.

Even our closest relatives, chimpanzees, are not exempt from this dividing line. Certainly, there is a large amount of anecdotal evidence of chimps helping each other or even saving each others’ lives. But some thinkers believe that this behaviour, along with other seemingly selfless animal acts, is actually self-serving in one of two ways.

The chimps could be helping their relatives in order to advanced the spread of its own genes, which family members are likely to share. Or they could be doing a favour for another individual, in the knowledge that it will be repaid later on. Either way, it’s the do-gooder that eventually benefits. Humans, on the other hand, seem to flaunt this rule. We often help others who are not relatives and who are unlikely to repay the favour. We go out of our way to be helpful, and sometimes even risk personal harm to do so.

In 2007, Felix Warneken and colleagues form the Max Planck Institute for Evolutionary Anthropology have found compelling evidence that we are not alone. Contrary to previous studies, they have found that chimps also behave altruistically in a very human way. They help out unrelated strangers without expectation of reward, and even go to great lengths to do so.

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From day to night – a lesson in eye evolution with the owl monkey

By Ed Yong | May 21, 2009 8:30 am

Blogging on Peer-Reviewed ResearchIn the forests of South America lives the unusual but aptly named owl monkey, or douroucouli. You could probably guess by looking at its large round eyes that it’s nocturnal, and indeed, it is the only monkey to be mostly active at night. But its eyes have many adaptations for such a lifestyle, beyond a large size.

The owl monkey’s retinas are 50% larger than those of a day-living monkey of similar size, like the brown capuchin. The proportions of different cells in their retina are also different. Owl monkeys have relatively few cone cells, which are responsible for colour vision and fewer ganglion cells, which process the signals from the cones. In contrast, they have many more rod cells, which are far more sensitive than cones and function best in low light, and rod bipolar cells, which transmit signals from the rods.

This is an eye that has sacrificed sharpness and colour for sensitivity. Nocturnal mammals the world over have developed a very similar suite of adaptations and according to Michael Dyer and Rodrigo Martins, these may be easier to evolve than you might think.

All of the cells in the retina are produced by a small group of stem cells called retinal progenitor cells (RPCs). As an embryo grows, its RPCs go through cycles of division, still maintaining their “stemness”. At some point, they leave this cycle and commit to becoming one of the various types of retinal cells. The fate they choose depends on when they leave the cycle. Those that are “born” early turn into cells that are important for daylight vision, such as cones and ganglions. Those that exit late become cells that play a greater role in night-vision, including rods and their bipolar cells.

This quirk of organisation means that the retina’s cells are always produced in a very specific order, with those that grant good night-vision cells appearing later. The upshot is that the owl monkey has been able to adapt its retina to see in the dark simply by tweaking the timing of its development. In its retinas, more RPCs commit to a particular fate later on in their cycle, producing fewer of the earlier types of cells and many more of the later ones. The result: an extra-sensitive retina with a complement of cells perfectly suited for nocturnal living, all triggered by a single change during development.  

The eyes of the owl monkey hammer home an increasingly familiar message – you can get big results by very subtly tweaking the way that bodies develop, without any need for large-scale tinkering. Even the eye, an exceptionally complex organ, can be altered in a coordinated way, simply by shifting the timing of its development. It’s why the owl monkey, in a relatively short space of evolutionary time, has converted the daylight-loving eyes of its ancestor into a nocturnal model.

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DNA sculpture and origami – a meeting of art and nanotechnology

By Ed Yong | May 20, 2009 1:00 pm

Blogging on Peer-Reviewed ResearchDNA is most famous as a store of genetic information, but Shawn Douglas from the Dana-Farber Cancer has found a way to turn this all-important molecule into the equivalent of sculptor’s clay. Using a set of specially constructed DNA strands, his team has fashioned a series of miniscule sculptures, each just 20-40 nanometres in size. He has even sculpted works that assemble from smaller pieces, including a stunning icosahedron – a 20-sided three-dimensional cage, built from three merged parts.

Douglas’s method has more in common with block-sculpting that a mere metaphor. Sculptors will often start with a single, crystalline block that they hack away to reveal the shape of an underlying figure. Douglas does the same, at least on a computer. His starting block is a series of parallel tubes, each one representing a single DNA helix, arranged in a honeycomb lattice. By using a programme to remove sections of the block, he arrives at his design of choice.

With the basic structure set down, Douglas begins shaping his molecular clay. He builds a scaffold out of a single, long strand of DNA. For historical purposes, he uses the genome of the M13 virus. This scaffold strand is ‘threaded’ through all the tubes in the design with crossovers at specific points to give the structure some solidity. The twists and turns of the scaffold are then fixed in place by hundreds of shorter ‘staple’ strands, which hold the structure in place and prevent the scaffold from unfolding.

The sequences of both the scaffold and staple strands are tweaked so that the collection of DNA molecules will stick together in just the right way. Once all the strands are created, they’re baked together in one hotpot and slowly cooled over a week or so. During this time, the staples stick to predetermined parts of the scaffold and fold it into the right shape. The slow cooling process allows them to do this in the right way; faster drops in temperature produce more misshapen forms.

The result: a series of six structures that Douglas viewed under an electron microscope: a monolith, a square nut, a railed bridge, a slotted cross, a stacked cross and a genie bottle. These basic shapes illustrate the versatility of the nano-origami approach, and they can also be linked together to form larger structures. Using staples that bridge separate scaffolds, Douglas created a long chain of the stacked cross units. Most impressively of all, he made an icosahedron by fusing three distinct subunits.

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MORE ABOUT: art, DNA, origami, sculpture

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