The No-Resolution Resolution: How to Really Be Happy in 2012
GOOD | DECEMBER 30, 2011
http://pulse.me/s/4uFo8
In mid-December, I celebrated my 30th birthday at a little Scandanavian restaurant in a quickly-changing part of DC. I was ... Read more
Codecademy Builds ‘Labs,’ A Web-Based Code Editor
TECHCRUNCH | DECEMBER 22, 2011
http://pulse.me/s/4fFpH
Smoking hot startup Codecademy, a service which teaches you how to program online has launched its Labs feature today, as a ... Read more
This New App Turns Your iPad Into Your Classroom
GOOD | DECEMBER 22, 2011
http://pulse.me/s/4f3On
Thanks to the popularity of the Khan Academy's simple video lessons, millions of people around the globe have learned ... Read more
(Sent from Flipboard)
Study: More Than 15% of Workers Get Hired Through Social Networks
READWRITEWEB | NOVEMBER 16, 2011
http://pulse.me/s/3dKQd
In a survey released today, recruiting software platform Jobvite noted that more than 22 million Americans used social networks ... Read more
Photographer Annie Leibovitz recommends iPhone as a camera
TUAW - THE UNOFFICIAL APPLE WEBLOG | NOVEMBER 16, 2011
http://pulse.me/s/3dANa
In the world of photography, there's one person who stands out for her classic portraits of such ... Read more
Like many other sites across the web, we’ve benefited from CC-licensed photos at Wired.com for years — thank you, sharers! It seems only fitting, and long overdue, to start sharing ourselves.
But the thinking here has to extend beyond the present and your own self. It reminds me a bit of the people who used to say that they needed a physical keyboard on their phone. And that Apple would eventually have to add one to the iPhone. It was a certainty.
(Sent from Flipboard)
Much of the power comes from IBM's carefully curated collection of data. Jennifer Chu-Carroll, one of the scientists who has worked on the project since it began over four years ago, says that Watson excels, predictably enough, when the answer is a detail stored in its database.
Lest we get too enamored with our technological prowess, however, the authors make some comparisons with biology. “To put our findings in perspective, the 6.4*1018 instructions per second that human kind can carry out on its general-purpose computers in 2007 are in the same ballpark area as the maximum number of nerve impulses executed by one human brain per second.”
http://www.wired.com/wiredscience/2011/02/world-computer-data/
Are you a tetrachromat? Probably not, but it is possible that the rare person is, with the super mutant power of enhanced color vision. OK – I would rather have Wolverine’s regeneration, but enhanced color vision would be cool.
Color vision in vertebrates is a result of the cones in the retina. Vertebrate retinas have two types of light-sensing neurons: rods see in black and white but have good light sensitivity, and so are specialized for low-light (night) vision. Cones are less sensitive than rods, but they respond to a specific range of wavelengths of light – i.e. color. By combining the color information from different cones with different wavelength sensitivities the brain is able to perceive a wide range of colors.
Different groups of vertebrates have different numbers of cones, and therefore a different range and ability to discriminate colors. Birds, for example, are tetrachromats – they have four different cones and can see farther into the ultraviolet than humans. In fact the common ancestor of tetrapod vertebrates was likely a tetrachromat. Most mammals are dichromats with only two cones. It is thought this reduction occurred during the early years of mammal evolution when our mammal ancestors were nocturnal and burrowing animals, and so needed night vision more than color vision.
Many primates, however, (including humans and our close relatives) are trichromats with three cones, and therefore have rich color vision, but not as good as birds. In fact our understanding of the genetics of cones and color vision provided yet another compelling line of evidence for evolution. Trichromatic primates do not have the same cones as their vertebrate ancestors. They did not regain one of the two cones that were previously lost. Mammals have two cones – an autosomal S-cone (a short wavelength sensitive cone), and an X-linked L/M cone (sensitive to median and long wavelength visible light and located on the X-chromosome).
Sometime after the divergence of new-world and old-world monkey, an old-world monkey ancestor underwent gene duplication of the X-linked cone gene. At first these genes would have been identical, but over time they diverged to become distinct cones with separated wavelength sensitivity. In humans these cone genes are 98% identical. The cones added sensitivity to red wavelengths and resulted in trichromacy.
The research into the evolution of color vision has also led to some interested findings about human color vision specifically. It seems that humans have a significant degree of variability in the sensitivity of the cones. You have probably heard that some people are partially color blind, because it is standard (at least in the US) to test all school children for color blindness. But you may not have known that there is variability in the other direction as well, and that there are cases of tetrachromacy in humans.
One possible mechanism for this is that women may inherit two different versions of an X-linked gene for color vision. Women have two X-chromosomes, and in each cell one X-chromosome is inactivated essentially at random. So the retina would have a mixture (a mosaic) of cones from the two versions on the two different X-chromosomes, functionally producing four different cones in the retina.
In one study they found that most women with this condition did not demonstrate tetrachromacy on color vision tests – they still functionally were trichromats. This is likely due to the fact that the cones were not different enough. Although some hypothesize that the optic nerve or perhaps the brain combines the information from these distinct cones and treats them as one stream of color information. However, going against this hypothesis is the fact that 1 in 24 such women (according to one study) demonstrated four-dimensional (or tetrachromatic) color vision. This means that the optic nerve is capable of carrying tetrachromatic vision and the brain is capable of interpreting it.
There may be other mechanisms as well that could result in true tetrachromatic vision in humans. These cases demonstrate the plasticity of biology and the brain in particular. It also demonstrates that spontaneous mutations can result in the addition of function – in this case expanded color vision. Not only has this almost certainly happened in our evolutionary past, but it is happening today in living humans. This is not likely to result in the evolution of tetrachromacy in humans in general for two reasons. The first is that, in our modern society, there likely isn’t any selective advantage to tetrachromacy. Our primate ancestors probably benefited from trichromacy – the speculation being that it enabled them to forage for fruit and vegetables better. But unless we lived in a world dominated by fashion designers and painters, it’s hard to see how tetrachomacy would provide a significant survival advantaged.
Second, humans are a large out-bred population. This does not mean that we are not evolving, but it makes it very unlikely that such a mutation will significantly spread throughout the population. It could by chance become prominent in an isolated population – the so-called founder effect. This has been demonstrated for inherited diseases, but can also occur with favorable mutations like tetrachromacy.
For now tetrachromacy remains in isolated individuals who are lucky enough to have their own mutant power.
--Brad
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