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Thursday, November 09, 2006

Neanderthals in Gene Pool, Study Suggests

Neanderthals in Gene Pool, Study Suggests

Published: November 9, 2006

Scientists have found new genetic evidence that they say may answer the longstanding question of whether modern humans and Neanderthals interbred when they co-existed thousands of years ago. The answer is: probably yes, though not often.

In research being published online this week by the Proceedings of the National Academy of Sciences, the scientists reported that matings between Neanderthals and modern humans presumably accounted for the presence of a variant of the gene that regulates brain size.

Bruce T. Lahn of the University of Chicago, the report’s senior author, said the findings demonstrated that such interbreeding with relative species, those on the brink of extinction, contributed to the evolutionary success of modern humans.

Other researchers in evolutionary biology said the new study offered strong support for the long-disputed idea that archaic species like Neanderthals contributed to the modern human gene pool.

Two other reports of DNA studies of possible mixing of human and related genes are expected to be published in the next few weeks.

Both genetic and fossil studies show that anatomically modern humans emerged 200,000 years ago in Africa and migrated into Europe 40,000 years ago. In about 10,000 years, Europe’s longtime inhabitants, Neanderthals, became extinct. The mainstream interpretation is that modern humans somehow replaced them without interbreeding.

In previous research, Dr. Lahn and associates discovered that a gene for brain size called microcephalin underwent a significant change 37,000 years ago. Its modified variant, or allele, appeared to confer a fitness advantage on those who possessed it. It is now present in about 70 percent of the world’s population.

The new research focused on the two classes of alleles of the brain gene. One appeared to have emerged 1.1 million years ago in an archaic Homo lineage that led to Neanderthals and was separate from the immediate predecessors of modern humans. The 37,000-year date for the other variant immediately suggested a connection with Neanderthals.

Dr. Lahn said it did not necessarily show that interbreeding was widespread. It could have been a rare, perhaps even single, event.

When I first saw the bust of Socrates in a museum in Athens, Greece, I said to myself, "Chi, this guy looks exactly like the reconstruction of a Neanderthal bust I've seen in various museums." Since then I've met many Neanderthal appearing people and they were usually very, very bright. It makes sense to me that there would have been some sexual interaction between the two groups. Human males will happily have sex with almost anything. Consider how syphilis spread to humans. Yup! Sheep.

Wednesday, November 08, 2006

Thinking Green

The article below is from New Scientist Magazine, Nov. 11, 2006. I have always thought this was the way to go since several millions of years of evolution have already done the research on the best way to trap sunlight for the production of energy. In fact, I don't see why we need to find synthetic mimics of the real thing. We should be able to use the actual product - deep sea algae for instance - grown in a medium such as agar agar. The trick would be in finding a way to convert the plant's energy into electricity or other forms of energy with producing greenhouse gases. We already use this green energy producer by way of burning wood or coal to produce heat which we then convert into electricity. Perhaps a simple combustion system which burns compacted algae so completely that very little particulate waste is produced and carbon dioxide could be reused to "fertilize" the algae would be possible.

Solar fuel cell
Solar fuel cell

IN JUST one hour enough solar energy reaches Earth's surface to meet all of our energy needs for an entire year. If we could come up with a way to harness this sunlight efficiently, it would solve all our energy problems at a stroke.

The trouble is: we are barely even beginning to exploit the full potential of solar energy. Solar cells only utilise a narrow range of frequencies, which means that even the most efficient and expensive cells typically convert only 17 per cent of the energy falling on them into electricity. Cheaper cells made of polymer coated with a thin film of titanium dioxide fare even worse, with an efficiency of just 10 per cent.

There is one notable exception to this inefficiency, however, a light-capturing technology that has the potential to revolutionise the rest of the field: plants. By developing synthetic versions of the pigment structures plants use to exploit even the faintest light levels, researchers believe they can make solar cells more efficient.

Some deep water algae, for example, have adapted to the tiny amount of sunlight they receive by growing rod-like structures called chlorosomes that contain thousands of light-harvesting pigment molecules. "They trap up to 97 per cent of the available photons," says Teodor Silviu Balaban of the Institute of Nanotechnology at the University of Karlsruhe in Germany.

In fact, all plants use similar "antennae" comprising stacks of pigment molecules, although most green leaves are more like 30 to 40 per cent efficient. Now Balaban and others are building artificial versions of these light-harvesting antennae. They plan to incorporate these into a new kind of solar cell, to develop photovoltaics that can absorb a greater amount of the available sunlight. Although they are unlikely to achieve the 97 per cent absorption rate of deep-water algae, the researchers hope to significantly improve on existing solar cells.

As a first step, a team led by Max Crossley at the University of Sydney in Australia has developed an antenna made up of synthetic porphyrins, a class of pigment molecules. The synthetic porphyrins absorb light across a broad range of frequencies, and more than 100 of the molecules can be assembled around a branching scaffold to mimic plant antennae, says Crossley. However, at the moment this process involves painstakingly constructing the antennae bond by bond, which is a slow process.

Much better, says Balaban, would be to find a way to make the antennae assemble themselves. One option for this is to use a technique called DNA origami to manipulate the molecules. This exploits the way that the complementary base pairs of DNA stick together, which is how the two sides of the double helix zip together. "It's been demonstrated that you can build 3D structures using DNA," says Rudy Diaz at the Arizona State University in Tempe, whose team has just received $1.1 million from the US National Science Foundation to develop the technique. By binding synthetic porphyrin molecules to unpaired DNA strands, and combining different strands, the team hopes to assemble 3D scaffolds containing large numbers of pigment molecules.

Balaban's group, in contrast, has gone a step further in mimicking plants, by uncovering the way antennae are constructed in nature. "I have copied nature's design for self-assembly," he says. The team studied natural plant antennae to identify how the pigment molecules bind together to create a stack. They were looking for the recognition groups - molecules that are attracted to porphyrins and so act like glue between the pigment molecules to bind them together. They identified a number of groups, including zinc, that form strong bonds with the pigment molecules, and are the key to antenna self-assembly. "They are like keys searching for their locks," says Balaban.

When the group began trying to construct artificial antennae by exposing the porphyrins to these molecules, they had no idea if the technique would work. "It was a gamble," he says. But it paid off: sure enough, the molecules bound together to form antennae. What's more, these antennae fluoresce when exposed to light, demonstrating that they are absorbing photons.

The cigar-shaped stacks can be tuned to harness specific frequency ranges of light by adjusting their size, says Balaban. To absorb light across the visible spectrum, the stacks typically need to be about 100 nanometres long, he says.

Balaban is now attempting to attach his antennae to a film of titanium dioxide, a vital step if the structures are to form the basis for low-cost thin-film solar cells. He also hopes to incorporate the light-harvesting structures in other existing types of solar cell, by coupling them to different semiconductor materials.

So how would the pigment molecules supply useful energy? In plants the light energy is transferred to a specialised chlorophyll molecule called P680, which releases a high-energy electron that can be used to reduce carbon dioxide to sugars. In a solar cell, the porphyrin molecules would transfer the photons to the semiconductor, where they would each knock loose an electron. Then, just as in a conventional photovoltaic device, these electrons would be corralled to generate a current.

However, improving the efficiency of solar cells by adding molecular antennae will not on its own turn solar power into a major energy source. What is also needed is a way to store solar energy so that it can be used at night or transported on demand, says Daniel Nocera at the Massachusetts Institute of Technology.

Nocera is working with Nathan Lewis at Stanford University in California to address this issue. They too are building photon-absorbing antennae, but rather than generating electricity, they plan to use them to produce hydrogen, which is more easily stored. In their version, the electrons liberated by the photons are used along with a catalyst to split water into hydrogen and oxygen (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0603395103). The hydrogen would then be stored for later use in fuel cells, says Nocera. The entire process would be closer to the way photosynthesis splits water into oxygen and hydrogen ions.

The idea of using renewable energy sources to produce hydrogen is not new, but by combining the two steps in a single device, the team believe they can not only increase the efficiency of the solar cells, but also eliminate the losses caused by transmitting the electricity to a separate device for splitting water. "This is integrating storage into photovoltaics," says Nocera.

Bringing the two steps together will take time, he admits, but if the team can marry plants' light-gathering ability with their talent for using this energy to produce chemical fuel, it will be worth the wait.

From issue 2577 of New Scientist magazine, 11 November 2006, page 30-31

Sunday, November 05, 2006


Everyone makes verbal gaffs in public speaking. It's only human. But the quantity and quality of the errors is something which tells us a lot about the speaker. This is so especially when the speaker doesn't seem to be aware at all - even after the fact - that he or she has made the error. When there are just too many stupid statements from one person, we must assume the person in question is intellectually challenged in some way. Right? So what are we to think of the following list?

"The vast majority of our imports come from outside the country. "
- George W. Bush

"If we don't succeed, we run the risk of failure."
- George W. Bush

"One word sums up probably the responsibility of any Governor, and that one word is 'to be prepared'. "
- George W. Bush

"I have made good judgments in the past. I have made good judgments in the future."
- George W. Bush

"The future will be better tomorrow. " George W. Bush

"We're going to have the best educated American people in the world. "
- George W. Bush

"I stand by all the misstatements that I've made."
- George W. Bush

" We have a firm commitment to NATO, we are a part of NATO. We have a firm commitment to Europe.
We are a part of Europe."
- George W. Bush

"Public speaking is very easy."
- George W. Bush

"A low voter turnout is an indication of fewer people going to the polls." - George W. Bush

"We are ready for any unforeseen event that may or may not occur. "
- George W. Bush

"For NASA, space is still a high priority."
- George W. Bush

" Quite frankly, teachers are the only profession that teach our children."
- George W. Bush

" It isn't pollution that's harming the environment. It's the impurities in our air and water that are doing it. "
- George W. Bush

"It's time for the human race to enter the solar system."
- George W. Bush

About Me

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I live on the Pacific slopes of the Talamanca mountain range in southern Costa Rica. My adult children live in the United States. I have a Masters Degree in Gerontology but have worked as a migrant laborer, chicken egg collector, radio broadcaster, secretary, social worker, research director, bureaucrat, writer, editor, political organizer, publicist, telephone operator, and more. My hobby of photography has garnered some awards.

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