5 posts categorized "Evolution"

08/14/2012

CT Scans Reveal Mysteries Of Shark's Teeth

SharkTeeth

Shark teeth are the longest-lasting piece of the animal -- their bones are cartilage and usually decompose quickly when a shark dies. But despite the longevity of shark teeth, marine biologists were unable to draw substantial conclusions about the animal because there was no good way to look at teeth structure.

That's all changed, using the technology of X-ray computed tomography, otherwise known as CT ("cat") scans.

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At Cornell University evolutionary biologist Willy Bemis, graduate student Josh Moyer and director of the Micro CT facility, Mark Riccio, decided to use CT scanner and the latest imaging software to look deep into the structure of shark's teeth. The images showed structural patterns that weren't visible before and allowed them to compare lots of teeth, answering questions about a sharks' growth, development and evolutionary history -- some of which had been lingering for at least a century.

"The thing is we can compare fossil and living shark's teeth," Bemis told Discovery News. "Because the technology is now cheaper, we can survey a large number of species in ways that were impractical in the past."

And shark teeth they do have: there are specimens that have been sitting around on shelves for years. One big advantage of the CT scan is that it's possible to see the teeth forming in the (dead) shark's head, without taking apart the specimen. The CT scan also shows an individual tooth's internal structure, which also changes as a shark ages. That reveals a lot about a shark's development, and doesn't require a scientist to slice up each tooth individually to peer inside.

CT scans were once a cumbersome business. Not only were the machines huge, but the computers and software needed to tease out images were expensive and the calculations for generating the images took a lot of time. But in the last decade, a combination of small CT machines and fast computers has made this kind of research feasible.

WIDE ANGLE: Shark Technology

Before CT scans, the definitive work on shark teeth was Bernhard Peyer's, "Comparative Odontology" in 1968. Peyer didn't have CT scanners, though, so he couldn't study how shark's teeth mineralize -- a basic, open question is exactly what that process looks like over time. Nor could he get a good look at the vasculature of the tooth. "There's been relatively little attention in the intervening time," Bemis said. He hopes to change that.

Image: Cornell University / Josh Moyer




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01/10/2012

Old Genes Make New, Giant-Headed Ants

Supersoldier-ant
Every animal carries a record of its past in its genes -- sometimes teeth show up in birds and vestigial limbs on snakes and whales. Ants are no exception. What if that potential could be tapped? And what brings it out?

That’s what a group of scientists at McGill University thought when they ran into a colony of ants on Long Island. A colony of ants known as Pheidole morrisi (more commonly called big-headed ants) had members we call soldiers with really outsized heads and bodies. These were called “super soldiers.”

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Pheidole, like many other ant species, are divided into castes, such as workers, queens and soldiers. Different foods are given to them when they are larvae, which triggers hormones that determine which caste the ant grows up to be.

Super soldiers occur naturally in some species of Pheidole in the southwestern United States and Mexico. But those living in upstate New York aren’t supposed to have the big heads. Ants are a pretty diverse lot and there are more than 1,100 species within even the Pheidole genus. But only eight of them naturally produce the super soldiers.

Biology professor Ehab Abouheif and PhD student Rajee Rajakumar wondered if the genes that build super soldiers were present in the Long Island ants all along, but were just waiting for some environmental factor to bring them out. The scientists first went to Arizona and collected two other species of ant in the same genus, Pheidole rhea and Pheidole obtusospinosa, which both have a subclass of super soldiers. They then observed how those two species developed their super soliders.

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Next, the scientists gave the young Long Island ants juvenile hormones at certain specific points in their development. In the Pheidole morrisi they got the super-soldier ants, which showed that the potential was always there. It just needed something to bring it out. One interesting phenomenon was the super soldiers had wing buds, which their cousins from Arizona did not. Many ant species develop wings as part of their development and ants and wasps share a common ancestor. The procedure worked in three different species of Pheidole, even though all three were separated by thousands of miles and millions of years of evolution.

Previously, few biologists thought such ancestral traits were important. They were just leftovers like the stuff in your attic. This shows that when necessary, nature has a “tool kit” that it can use to create big morphological changes -- some of them new.

Via: McGill University

Image: Alexander Wild

 



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01/25/2011

Robot (R)evolution On The Way

Bot-tots-400

At the University of Vermont, the robots are learning about their bodies. Bot-tots who come online flat on the floor like babies and then gradually find upright positions, learned how to walk many times faster than their pre-positioned counterparts. Turns out learning in small steps -- how to crawl before standing before walking -- makes for a better adapted robot in the real world. So if you're giddy for a future robo-maid, start preparing the nursery since it may have to be “raised” before it can bring you breakfast in bed.

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The research is being conducted by evolutionary robotics researcher Josh Bongard. He and his colleagues team did a computer simulation before busting out the Legos (he really did this later, using some Lego Mindstorm kits). In 5,000 3-D simulations, they discovered that the body-changing bots starting on the ground figured out how to move to a target in just minutes versus the hours it took upright-starting bots to do the same. Presumably, beginning in a walk rather than a crawl meant those bots needed to master balance while simultaneously mastering motion -- a harder task.

Then Bongard built robot skeletons with twelve moving parts, and watched them learn to while shifting form. In the physical world, these quadruped bots needed braces over their limbs to gradually tilt their frames upright. But as expected, the evolving bots started learning to move on the ground before gradually adding in vertical balance and achieving a standing stride.

Robot Can Read, Learn Like a Human

But why bother making robot bodies evolve at all? Wouldn't we rather have all our machines perform a task perfectly as soon as we hit “on”? The idea is to create robots that can adapt to changing, unpredictable environments, like construction sites or even the home. A machine that figures out how to get back up on its own after being tipped over is far more useful than one who needs a babysitter all the time. That solved, all we'd need to do is teach the robots how to raise each other...

Viva la revolution!

Read the UVM story for more, and watch this YouTube video of the simulated and physical bots:

Get More Robots from PlanetGreen -- Slideshow: Meet BigDog, a Soldier's Robotic Best Friend
Photo: University of Vermont


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05/12/2010

Is Love Blind?

Love-blind-650x650
Shakespeare wrote in The Merchant of Venice that “love is blind and lovers cannot see.” More than 400 years later, brain imaging has offered some scientific support to that iambic verse.

Looking at a brain in love is like watching a neurological fireworks display.

The ventral tegmental area and ventral striatum, nestled in the center of the brain, light up excitedly as the neurotransmitters dopamine and norepinephrine spring into action, causing a person to have short attention spans, feel giddiness and crave the object of her desire.

A 2005 study by Rutgers University biological anthropologist Helen Fisher and colleagues examined the fMRI brain scans of 17 men and women who reported being truly, madly in love. Each of the images showed the same activity in the brain’s reward system as that which occurs in the brain of a cocaine addict.

What’s more, the love-struck participants could readily tick off traits or characteristics they didn’t particularly like about their beloveds, but under the influence of pleasure-enhancing dopamine and other monoamines, they quickly overlook those faults.

“Once you fall in love with somebody, once they trigger the brain system for falling in love, love is blind, no question about that,” said Fisher, who recently wrote Why Him? Why Her?, which explores the neurological underpinning of romance.

And once people fall in love, they’re essentially at the mercy of the brain’s reward system until the neurotransmitters oxytocin and vasopressin, which are associated with long-term bonding, produce their calming, stabilizing effect.

But before that dizzying dopamine-fueled process even begins, Fisher told Discovery News that people have much more power to decide who’ll receive their affections.

“Love is extremely blind once you’ve chosen your partner, but it’s not so blind while you’re making that choice,” Fisher said. “Basically, this concept of who you choose, it’s like a funnel. At any point, there are breaking points, moments where it’s just not going to work."

Mate selection -- as opposed to being in love -- is fairly pragmatic, in fact.

People subconsciously select mates who come from common socioeconomic backgrounds, ethnicities, geographies, education levels and upbringings. 

For better or worse, we tend to pick potential partners who are a lot like us.

So while we’re searching around for a sweetheart, the ball is our court to reject those who don’t share commonalities and mesh with what Fisher calls our “love maps,” or the temperaments and features we develop attractions to from childhood. That way, we don’t fall for just anyone.

“In other words, you and I can walk into a room and if everyone was a Pygmy and came up to our hips, we probably wouldn’t fall in love with them…because they’re too unfamiliar,” Fisher explained.

Gordon G. Gallup, an evolutionary psychologist at State University of New York at Albany agrees that people are generally more drawn to others with mutual interests and backgrounds.

“At least for the development of healthy, long-term relationships, it’s not the case that opposites attract,” said Gallup, an expert in interpersonal attraction.

In addition to the lifestyle and temperamental traits that draw two people together, Gallup’s extensive research has also found that innate physical attraction is far from blind. Instead, it engages all of our senses to detect whether someone is a reproductive match.

Take hearing someone’s voice, for instance.

Gallup and fellow researchers found that for women who aren’t taking birth control, their voices are rated as most attractive during the middle of their cycle when they’re most fertile.

Furthermore, Gallup’s studies indicate that hourglass figures for women and wedge-shaped bodies for men also subconsciously signal greater reproductive potential.

“So first impressions, like when you first meet somebody, involve a convergence of information in the visual domain and the auditory domain,” Gallup said.

When that convergence grabs our lusty attention, and passionate kissing eventually ensues, Gallups says an even more potent information exchange occurs.

“The first kiss may not make a relationship, but it can clearly break a relationship,” Gallup said. “What happens is a lot of information from a lot of different modalities is brought to bear on the first kiss -- the posture, the odor, the extent to which there’s an open mouth kiss, the extent to which there’s an exchange of saliva.”

That intimate interaction subconsciously communicates prospective mates’ genetic and interpersonal compatibility, which explains why human culture has attached such deep meaning to an otherwise unremarkable form of physical contact.

Circling back to Fisher’s research, an explosive, heart-pounding first kiss can ignite that blinding neurological love reaction, activating the dopamine reward system and setting off an addictive response to one’s beloved.

But while humans are hard-wired to fall in love intensely, those neurochemical blinders eventually wear off as we settle into relationships.

Fisher’s studies have also shown that, as with drugs, people develop a tolerance for the neurotransmitters that produce the head-over-heels feelings and excitement of early love.

“By and large, we are an animal that pairs up to rear our young,” Fisher said.

How long that euphoric pair bonding lasts, however, is the more unanswerable question, varying from person to person – or lover to lover, as Shakespeare would probably say.

08/03/2009

Shark Teeth Tear Open Climate Mysteries

Tigershark Sharks outlasted the dinosaurs, so it's fitting that they have the potential to tell us quite the story about Earth's climate. Fortunately, getting that won't require messing with them.

Evolutionary biologist and Caltech postdoc Rob Eagle along with his colleague Aradhna Tripati, an assistant Earth sciences professor at UCLA, have discovered a direct link between shark teeth and ocean temperatures.

Continue reading "Shark Teeth Tear Open Climate Mysteries" »

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