February 15, 2013 7:45 pm

Darwin’s origin of the pigeon

A study unravels the genetics of the bird species
rock pigeons©Courtesy Sydney Stringham

All you need is dove: pigeon breeds such as the Old German Owl (left) and Scandaroon (right) all derive from the wild rock dove. Background shows the classification scheme proposed by Charles Darwin in 1868

If time travel had given Charles Darwin a magic preview of scientific papers appearing in 2013, he would have been particularly pleased with one just published in Science that unravels the genetics of pigeons.

Darwin was the most famous pigeon fancier in history. During the 1850s and 1860s he bred ever fancier birds at Down House, his home in Kent, to support his research into evolution. Through artificial selection of pigeons with elaborately shaped and coloured feathers, he gained insights into the far slower process of natural selection.

The Science study decodes the genomes of domesticated, feral and wild pigeons – confirming Darwin’s view that the myriad domesticated breeds, which vary in appearance almost as much as dogs, all derive from the wild rock dove Columba livia.

The DNA analysis shows that wild doves were originally domesticated in the Middle East about 5,000 years ago, probably from birds that gathered around grain stores, and were bred first for food and then fancy looks. Their descendants today make up around 350 breeds.

The exploitation of pigeons’ navigational skills, which enables the birds to race home when released hundreds of miles away, may have taken place further east in Iran and India as well as in the Mediterranean region. Feral pigeons, which make a nuisance of themselves in cities around the world, are descended from racing pigeons that never made it home and began to breed in the wild.

One of the most popular features of fancy pigeons is the crest – feathers on the back of the head and neck that grow upwards rather than downwards as in wild pigeons. “Some are small and pointed,” says lead author Michael Shapiro of the University of Utah. “Others look like a shell behind the head; some people think they look like mullets. They can be as extreme as an Elizabethan collar.”

Genomic analysis shows that a mutation in a single gene called EphB2 controls whether or not a crest grows. It works in pigeon embryos by reversing the direction of the “buds” from which feathers later grow. Other (still unknown) genes determine what type of crest develops: shell, peak, mane or hood.

The researchers compared the pigeon with the chicken and zebra finch genomes. “Despite 100 million years of evolution since these bird species diverged, their genomes are very similar,” says Shapiro.

The next step will be to track down more of the genetic changes responsible for pigeons’ fanciness. “Darwin used this striking example to communicate how natural selection works,” Shapiro says. “Now we can get to the DNA-level changes that are responsible for some of the diversity that intrigued Darwin 150 years ago.”

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How to fly a spaceship – with your mind

Two minds are better than one when it comes to controlling a spacecraft by the power of thought, according to a collaborative study by the University of Essex and Nasa’s Jet Propulsion Lab in Pasadena, California.

The researchers used BCI (brain-computer interface) technology, which is being developed at Essex and elsewhere to convert electrical signals from the brain into control commands for various applications, including virtual reality and hands-free control. It is particularly useful in helping disabled people control a computer cursor, mouse or wheelchair: the user learns to carry out mental tasks that the computer translates into movement.

The university is extending its research into “collaborative BCI” in which multiple users work together by combining their brain signals. In the £500,000 project with Nasa, two people tried to steer a virtual spacecraft to a planet on a computer screen, using directional dots on a cursor.

They wore electroencephalography (EEG) caps with electrodes, which picked up different patterns in their brainwaves depending on where they focused their attention. The computer merged brain signals representing their chosen direction in real time, to produce control commands for steering the spacecraft.

Essex professor Riccardo Poli says the experiment required intense thought. The path was more accurate with two players because if one had a brief lapse in concentration the other would compensate.

Combining signals also helped to reduce the random “noise” that hinders EEG signals, such as heartbeat, swallowing and muscle activity. “When you average signals from two people’s brains, the noise cancels out a bit,” says Poli.

The Essex team believes BCI research could also help, for example, a committee to make a decision based on the real majority view, rather than following the most outspoken – or bullying – individuals.

spintronic' chip©Lindenartwork

The 'spintronic' chip takes data storage into a new dimension

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The chips are down, up, left and right

Scientists at the University of Cambridge have made the world’s first microchip that allows information to travel in three dimensions, using “spintronics” (or spin electronics), writes Ling Ge. The spintronic chip exploits the electron’s tiny magnetic moment or “spin”, unlike traditional chips that use its electric charge. Conventional microchips can only pass digital information across a single plane – left to right and front to back. However, the Cambridge researchers have succeeded in moving data up and down as well.

“Today’s chips are like bungalows – everything happens on the same floor. We’ve created the stairways, allowing information to pass between floors,” says Reinoud Lavrijsen, an author of the study, which appears in the journal Nature.

The research could be excellent news for the electronics industry, making it possible to store more data on chips by allowing information to be spread across several layers, rather than compacted into one.

Bright spark

Comet

Comet Ison could be the “comet of the century” – as bright as a full moon – when it nears the sun next winter. Or, because comets are notoriously unpredictable, it could break up or fizzle out first.

Using current chip architecture, Moore’s Law – the 1965 prediction by Intel co-founder Gordon Moore that the electronics industry could double the number of transistors on a chip every two years – will eventually reach the limit of miniaturisation at atomic levels.

Spintronics could extend the life of Moore’s law. Spintronic chips are increasingly being used in computers, and they will become the standard memory chip and the basis for super-high density hard drives within the next few years, according to the researchers.

To fabricate the microchip, the team uses an experimental technique called sputtering, a process in which atoms are ejected from a solid target by bombarding it with energetic particles. This produces a sandwich of cobalt, platinum and ruthenium atoms on a silicon chip. The cobalt and platinum atoms store digital information in a similar way to a hard drive. The ruthenium atoms act as messengers, communicating the information between neighbouring layers of cobalt and platinum.

“Each step on our spintronic staircase is only a few atoms high. I find it amazing that by using nanotechnology not only can we build structures with such precision in the lab, but also, using advanced laser instruments, we can actually see the data climbing this nano-staircase step by step,” says Russell Cowburn, who led the project.

“This is a great example of the power of advanced materials science … This is the 21st-century way of building things – harnessing the basic power of elements and materials to give built-in functionality.”

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