Netbook sales aren't as brisk as they used to be, and some are blaming the iPad. Well, Morgan Stanley's released an enlightening chart that pegs the victims of the iPad as, well, just about everything. It just makes people anxious. More »
After jailbreaking your iPad, you can install SNES4iPhone, which will not only play SNES romz—it will open the Bluetooth stack, allowing you to play Mario with a Wiimote. Nintendotacular! [Instructions via SwagLikeMe via notcot] More »
John Hawks has a very long post up. This part caught my attention:
We don’t really know the answers, but now we have a chance to test hypotheses about ancient population size and expansion in Neandertals. My point at the moment is only this: If today Neandertal genes make up only one percent of the gene pool of the 5 billion people outside Africa, that’s the genetic equivalent of 50 million Neandertals.
As Hawks notes later, this paper comes pretty close to resolving whether Neandertals were of the same species as we moderns, at least using the biological species concept. There were fertile hybrids. That should not be too surprising, a few years ago when the Neandertal introgression story was big I looked into mammalian embryology, and our lineage had to be very special as mammals went for their to be inter-population sterility.
This is not just a science story. Dave Chamberlain observes:
Anyone else notice that the artists depictions of neanderthals have slowly changed from stupid brute monkey men to ruggedly handsome moderns with a protruding brow? Hmmm, I bet they get even more good looking now. Hawks promises all neanderthals all the time, I for one can’t get enough of it.
I think that this will change our perceptions, and “artists’ renderings” quite a bit. A few years ago when it seemed that Neandertals may have been highly depigmented I observed that it was a bit strange that in most depictions they tended to be rather dark and swarthy as Europeans go (most famously in Jean Auel’s work the H. sapiens sapiens were Aryan Übermensch while the Neandertals were small and dark). I think some of the same subconscious dynamic was at play as when Tom Coburn was outraged at the TV nudity of Schindler’s List. Coloured people naked on a National Geographic special is one thing, but white people should be decent! (and please, don’t accuse me of seeing racism where it isn’t. If you know me you know that I’m not super-obsessed with that sort of thing, but I think it’s pretty obvious that there’s a lot of implicit assumptions which go into being a white European, and how one views someone and how they should behave)
From detnews.com - Autos Insider:
Detroit's Big Three automakers and Toyota Motor Corp. will endorse mandatory event data recorders and brake override systems on all new vehicles. Dave McCurdy, president and CEO of the Alliance of Automobile Manufacturers, the trade group repres
Bacon is divine. (Although far from my favorite pork.) But can we all agree that bacon-as-a-flavor has run its course? If you're pouring bacon syrup into coffee you're just stunt casting. Bacon is the racist Robert DeNiro of flavorings. [Torani] More »
The leaking oil pipeline in the Gulf of Mexico is gearing up to be the worst environmental disaster in American history. It’s still second to the Exxon Valdez incident, but at this rate it will pass the Alaska spill soon. Reading about this is breaking my heart, and angering me a lot. It’s difficult to express in words how truly awful this is… so maybe a picture will help.
This image, taken by NASA’s Aqua satellite, shows the slick as it was on May 4 — well over 50 km (30 miles) long and growing. An earlier image shows the slick when it was half that size, just three days earlier. "Alarming" is a terribly understated word to say the least. Against the natural browns and greens of the land, and the steely blue of the Gulf waters, the gray of the oil is threatening, menacing, sick. It reminds me of The Black Thing from A Wrinkle In Time.
Efforts are underway to mitigate the leak — more on that in a later post — but I want to point out that these satellite images are useful to those on the ground, so to speak, to track the growth and spread of the oil. The efficacy of space exploration may not spring to mind when contemplating environmental disasters, but it’s there nonetheless.
I have one more thing to add, which is somewhat contrary to my point above. There is an irony here: Some images of the leak from space almost make this disaster look less impacting. Here is a shot taken by astronaut Soichi Noguchi, as the space station flew past the Gulf on May 5:
This picture is actually lovely, which is such a disturbing dichotomy from reality! It’s difficult to see how truly apocalyptic 200,000 gallons a day of crude oil gushing up from the sea floor is when looking at this — and it may get far worse.
I am not implying any deeper meanings to this second image, though you may feel free to take away whatever metaphor you wish. But pictures themselves are only telling us a story. It’s up to us to interpret them, and to extract what useful information we can.
In all the debate over who has the best plan for NASA, I think something important has been lost. Right now, I think destinations and architectures aren’t as important as articulating a coherent vision for a space program relevant to America’s needs and values.
Given the shock that has accompanied the pending Shuttle retirement, the continuation of a Space Station that I doubt most Americans know exists, and the proposed cancellation of the Constellation Program (that I think even fewer Americans really knew about), I think it’s clear that we haven’t done that. Instead, we have people arguing back and forth over what largely amount to platitudes. I hear friends and colleagues, who are understandably disenchanted with the political process, wishing aloud that the government would just give us the money to go do what we want and leave us alone.
That’s never going to happen, of course. Whether civil servant or contractor, all of us involved in NASA’s human space flight endeavors are stewards of the taxpayers’ money. Members of Congress and the President are the duly elected representatives of those same taxpayers. Between the Executive and Legislative branches of our political triad, policy is crafted, funded, and executed. Human space flight is inherently tied to the political process and we fail to bridge the technical and policy worlds at our own peril.
There have been many strategies put forth to try to help NASA better navigate the winds of political change. Most that I’ve seen propose some mechanism to make it more difficult for politicians to change course mid-stream. The politicians control the purse strings, so that’s never going to happen, either.
I think the most effective strategy for NASA exists at a much more basic level. It’s something I always kinda knew in the back of my head, but I didn’t really learn how to start explaining it better until I had the opportunity to serve on the Barrier Analysis Team for JSC’s Inclusion and Innovation Council. Mark Craig, a NASA veteran and senior executive at SAIC, was one of the mentors for our team and I think I learned more from him than anyone else over that period.
If you keep up with OpenNASA, you’ll know that this isn’t the first time I’ve broached the subject. I think NASA’s best defense is to design and pursue programs and strategies that are relevant because they contribute to solving America’s strategic problems.
On May 5th, I had the opportunity to listen to Mark discuss this topic in more detail. He was gracious enough to let me share here on OpenNASA what I took away from his talk.
Since it was presented under the auspices of the JSC Storytelling program, Mark opened up by defining what a “story” is, according to his friend and colleague, Bob Rogers. A story is ” a deeper level of truth by which we explain the world and our place in it to ourselves.” (Note: Ask yourself how you explain, honestly, the world and your place in it. How do you relate that story to other people? We’ll come back to that.)
Mark also explained that he sees relevance as having two parts. There is the “why” and the “value.” “Why Relevance” explains our reason for being. It tells us where we go and what we do. Mark offered the statements of the Augustine Committee and John Marburger, OSTP Director under President Bush, as examples. The Augustine Committee said we go into space to expand the human presence in the Solar System, while Marburger stated that our goal was “to advance U.S. scientific, security, and economic interests through a robust space exploration program.”
These statements aren’t necessarily contradictory, but they illustrate different perspectives on the “why” that must be taken into account.
“Value relevance” is defined by Mark as a “critical mass” of benefit delivered to a “critical mass” of stakeholders. This recognizes that you probably can’t please everyone, but you can and should satisfy enough of your stakeholders to press on. This form of relevance must actually be experienced by the stakeholders, though. We can’t just go do something that we think is great and, then, try to sell it to everyone else. Value relevance is fostered through a continual process of research (identify what is important to your stakeholders), creation (make something that meets their needs), delivery (make sure they get it), and self-improvement (evaluate how well you did the last iteration).
This is not just a communications problem. We’ve labored under the assumption for far too long that we don’t do a good enough job “selling” the space program to the public. Mark rightly points out that this process of creating value relevance must be built into architectures and designs early on. The research part is key because we have to meet other people where they are to effectively engage them, both on a technical and emotional level. One commenter in the audience noted that, in the business world she came from, you have to know your audience or you will fail.
Mark also had a few recommendations and “Red Flags” for us to consider. First, he advocates the creation of an external guidance and accountability function, similar to the Decadal Survey process, for human space flight. Having an external group of “thought leaders” in science, industry, art, and culture would provide the outside perspective that we in the human space flight community lack. This would help keep us from drinking our own bathwater.
NASA would also need its own value management system to engage external marketing experts, employ industry best practices in value management, and document the structure in NASA processes. This gets back to the point about needing to build value relevance into our system early on.
From his experience as a NASA veteran and consultant to museums, Mark also suggested some areas where we could make a real impact. For example, the movie Apollo 13 was compelling because it showed, in detail, what the people went through. NASA TV’s view of Mission Control, by comparison, looks like a security camera. We have experiences and emotions to share with the public. Why don’t we?
Mark also believes that we could be doing more in the area of medical research for the benefit of people here on Earth. My personal opinion is that we have a similar opportunity in the area of energy. American-owned and operated powersats and miniaturized, passively-safe nuclear power could revolutionize both industry and space exploration while giving us avenues to reduce our dependence on fossil fuels.
Changing our approach to how we build and conduct the space program doesn’t just involve top-down management, though. Mark also identified what he called “red flags” for us to push back against when we see them.
I agree with Mark’s argument that we can build human space flight into the fabric of society, if we can build relevance and accountability into the human space flight program. We just have to remember that this is relevance that is researched, understood, and delivered; not just assumed.
So, with that in mind, I ask you to consider the following questions.
What is the compelling story for the human space program?
How can we make it relevant to America’s needs and values?
How you can be a part of changing the narrative?
I’m still digesting the papers on the Neandertals which just came out. You can find them here. If you have questions, please read the papers first. They’re open access, so free to all. There’s a lot to mull over, and I don’t know what I can add right now, but I will note:
1) There’s a lot of stuff that doesn’t have to do with admixture, but focuses on genes where Neandertals and modern humans differ. There is for example an enrichment of differences in genes which relate to skin morphology. But my friends who think that modern human uniqueness can’t be pinned down to changes in SNPs will probably feel even more validated by this paper.
2) The fact that non-Africans as a whole, including Papuans, have Neandertal admixture, presumably from interactions in the Middle East, seem close to falsifying the “two-wave” model of expansion “Out of Africa” which came to prominence in the early aughts. That is, one group of Africans went north through the Middle East, and another swept along the Indian ocean fringe and onto southeast Asia. If there were two waves then they interacted a lot because they both received the same proportion of Neandertal alleles, which makes the idea of two genetically distinct waves a bit useless.
Mobile Spy's iPad Spy is a new app for jailbroken iPads that will let you keep track of what the iPad is being used for with the user being none the wiser. Creepy! More »
I need to create an interference fit between a Ø.7500-7505 shaft consisting of alum 6061 t-6511 and a Ø.7495-.7500 journel consisting of 17-4 stainless. In freezing the 6061 t-6511 how much shrinkage will occur and will it be enough to where i wont have to heat the 17-4 journal?
From Popular Science - New Technology, Science News, The Future Now:
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Russian regional president Kirsan Ilyumzhinov claims he was abducted by aliens. Now, a Russian MP has asked President Dmitry Medvedev to investigate his claims to make sure he didn't give any state secrets to the space visitors. More »
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For lovers of stellar beauty, the Herschel space telescope may have already earned its keep. Just one year after its launch, researchers from the European Space Agency have released this stunning image of a massive star being born in a vast bubble of cold dust.
Herschel’s far-infrared detectors are finely attuned to stellar nurseries. When a star begins to form, the dust and gas surrounding it heats up to a few tens of degrees above absolute zero, and it begins to emit far-infrared wavelengths. In the galactic bubble shown, known as RCW 120, the newborn star is the white blob at the bottom of the bubble.
The “baby” star is perhaps a few tens of thousands of years old. It is some eight to 10 times the mass of our Sun but is surrounded by about 200 times as much material. If more of that gas and dust continues to fall in on the star, the object has the potential to become one of the Milky Way Galaxy’s true giants [BBC].
Giant stars pose a particular challenge to our understanding of star formation, researchers say. Present theories suggest that stars that are larger than about 10 solar masses shouldn’t exist, because their fierce radiation should blast away the clouds that feed them materials to grow on. Yet astronomers have spotted stars that have 120 times the mass of our Sun.
Click through the gallery for a couple more amazing shots from Herschel.
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dear problem solvers.
please explain for 10 ton outdoor air cooled 400 volts package unit is it necessary that the suction and return ducts must be connected with Flexible joints to the package unit suction and return openings.if answer is yes than what is the reason for this.Thanks
From Discover Magazine | rsslist:
The Japanese mission Hayabusa ("Falcon") has been nothing if not ambitious. Launched in 2004, it reached the bizarre asteroid Itokawa a little over a year later. It took phenomenal images and other measurements, and even landed on the asteroid its
Read Carl Zimmer’s post, Skull Caps and Genomes. The papers aren’t on the Science website yet. And of course, Google News. I think I’m just going to wait on the papers before I say much more….
Good time to be alive, no?
Update: John Hawks.
Update II: Science got the page up.
NASA Presentations on New Space Plans for FY2011, Planetary Defense
"Lori Garver, Ed Weiler, Bobby Braun, and Laurie Leshin (all from NASA) presented at a meeting in Washington, D.C. on 05 May 2010 aspects of the new NASA plan, specifically those elements involved with the new NASA budget. I have posted these docs to the Google Docs library (General) for this site."
The skull cap is thick and flat. It looks distinctively human, and yet its massive brow ridge, hanging over the eyes like a boney pair of goggles, is impossible to ignore. In 1857, an anatomist named Hermann Schaafhausen stared at the skull cap in his laboratory at the University of Bonn and tried to make sense of it. Quarry workers had found it the year before in a cave in a valley called Neander. A schoolteacher had saved the skull cap, along with a few other bones, from destruction and brought it to Schaafhausen to examine. And now Schaafhausen had to make the call. Was it human? Or was it some human-like ape?
Schaafhausen did not have much help to fall back on. At the time, archaeologists had only found faint hints that humans had coexisted with fossil animals, such as spears buried in caves near the bones of hyenas. Charles Darwin was still two years away from publishing the Origin of Species and providing a theory to make sense of human evolution. Naturalists tended to look at humanity as a collection of races arranged in a rank from savagery to civilization. The most savage races barely ranked above apes, while the naturalists themselves, of course, belonged to the race at the top of the ladder. When anatomists looked at human bodies, they found what they thought was a validation of this hierarchy: differences in the size of skulls, the slopes of brows, the width of noses. Yet all their attempts to neatly sort humanity were bedeviled by the tremendous variation in our species. Within a single so-called race, people varied in color, height, facial features–even in their brow ridges. Schaafhausen knew, for example, about a skull dug up from an ancient grave in Germany that “resembled that of a Negro,” as he later wrote.
To make sense of the “Neanderthal cranium,” as he called it, Schaafhausen tried to fit it into this confusing landscape of human variation. As peculiar as the bone was, he decided it must belong to a human. It was very much unlike the cranium of living Europeans, but Schaafhausen speculated that it belonged to an ancient forerunner. Yet for naturalists of Schaafhausen’s age, such a heavy brow ridge implied not the advanced refinement of European civilization, but wild savagery.
Well, Schaafhausen thought, Europeans were pretty savage back in the day. “Even of the Germans,” Schaafhausen wrote in his report on the Neanderthal cranium, “Caesar remarks that the Roman soldiers were unable to withstand their aspect and the flashing of their eyes, and that a sudden panic seized his army.” Schaafhausen found many other passages in classical history that suggested to him a pracitically monstrous past for Europe. “The Irish were voracious cannibals, and considered it praiseworthy to eat the bodies of their parents,” he wrote. Even in the 1200s, ancient tribes in Scandinavia still lived in the mountains and forests, wearing animal skins, “uttering sounds more like the cries of wild beasts than human speech.”
Surely this heavy-browed Neanderthal would have fit right in.
Some 150 years later, pieces of that original Neanderthal cranium now sit in another laboratory in Leipzig, just 230 miles away from Schaafhausen’s lab. Instead of calipers, it is filled with a different set of measuring tools: ones that can read out sequences of DNA that have been hiding in Neanderthal fossils for 50,000 years or more. And today a team of scientists based at the Max Planck Institute of Evolutionary Anthropology published a rough draft of the entire Neanderthal genome.
It is an historic day, but it reminds us, once again, that the publication of a genome does not automatically answer all the questions scientists have about the organism to whom the genome belongs. In fact, a careful look at the new report is a humbling experience. We gaze at the Neanderthal genome today as Schaafhausen gazed at the Neanderthal skull cap that first introduced us to these ambiguous humans.
Since Schaafhausen’s day, paleoanthropologists have discovered Neanderthals across a huge range stretching from Spain to Israel to Siberia. Their fossils range from about 400,000 years ago to about 28,000 years ago. Instead of a lone skull cap, scientists now have just about every bone from its skeleton. Neanderthals were stocky and strong, with a brain about the size of our own. The isotopes in their bones suggest a diet rich in meat, and their fractured bones suggest a rough time getting that food. There’s no evidence that Neanderthals could paint spectacular images of rhinos and deer on cave walls like humans did. But they still left behind many traces of very sophisticated behavior, from intricate tools to painted jewelry.
Ideas about our own kinship to Neanderthals have swung dramatically over the years. For many decades after their initial discovery, paleoanthropologists only found Neanderthal bones in Europe. Many researchers decided, like Schaafhausen, that Neanderthals were the ancestors of living Europeans. But they were also part of a much larger lineage of humans that spanned the Old World. Their peculiar features, like the heavy brow, were just a local variation. Over the past million years, the linked populations of humans in Africa, Europe, and Asia all evolved together into modern humans.
In the 1980s, a different view emerged. All living humans could trace their ancestry to a small population in Africa perhaps 150,000 years ago. They spread out across all of Africa, and then moved into Europe and Asia about 50,000 years ago. If they encountered other hominins in their way, such as the Neanderthals, they did not interbreed. Eventually, only our own species, the African-originating Homo sapiens, was left.
The evidence scientists marshalled for this “Out of Africa” view of human evolution took the form of both fossils and genes. The stocky, heavy browed Neanderthals did not evolve smoothly into slender, flat-faced Europeans, scientists argued. Instead, modern-looking Europeans just popped up about 40,000 years ago. What’s more, they argued, those modern-looking Europeans resembled older humans from Africa.
At the time, geneticists were learning how to sequence genes and compare different versions of the same genes among individuals. Some of the first genes that scientists sequenced were in the mitochondria, little blobs in our cells that generate energy. Mitochondria also carry DNA, and they have the added attraction of being passed down only from mothers to their children. The mitochondrial DNA of Europeans was much closer to that of Asians than either was to Africans. What’s more, the diversity of mitochondrial DNA among Africans was huge compared to the rest of the world. These sorts of results suggested that living humans shared a common ancestor in Africa. And the amount of mutations in each branch of the human tree suggested that that common ancestor lived about 150,000 years ago, not a million years ago.
Over the past 30 years, scientists have battled over which of these views–multi-regionalism versus Out of Africa–is right. And along the way, they’ve also developed more complex variations that fall in between the two extremes. Some have suggested, for example, that modern humans emerged out of Africa in a series of waves. Some have suggested that modern humans and other hominins interbred, leaving us with a mix of genetic material.
Reconstructing this history is important for many reasons, not the least of which is that scientists can use it to plot out the rise of the human mind. If Neanderthals could make their own jewelry 50,000 years ago, for example, they might well have had brains capable of recognizing themselves as both individuals and as members of a group. Humans are the only living animals with that package of cognitive skills. Perhaps that package had already evolved in the common ancestor of humans and Neanderthals. Or perhaps it evolved independently in both lineages.
In the 1990s, the geneticist Svante Pääbo led a team of scientists in search of a new kind of evidence to test these ideas: ancient DNA. They were able to extract bits of DNA from bones that were found along with Schaafhausen’s skull cap in the Neander valley cave. Despite being 42,000 years old, the fossils still retained some genetic material. But reading that DNA proved to be a collossal challenge. Over thousands of years, DNA breaks into tiny pieces, and some of the individual “letters” (or nucleotides) in the Neanderthal genes become damaged, effectively turning parts of its genome into gibberish. It’s also hard to isolate Neanderthal DNA from the far more abundant DNA of microbes that live in the fossils today. And the scientists themselves can contaminate the samples with their own DNA as well.
Over the years,Pääbo and his colleagues have found ways to overcome a lot of these problems. They’ve also taken advantage of the awesome leaps that genome-sequencing technology has taken since they started the project. They have been able to reconstruct bigger and bigger stretches of DNA. They’ve been able to fish them out of a number of Neanderthal fossils from many parts of the Old World. And today they can offer us a rough picture of all the DNA it takes to be a Neanderthal.
To create a rough draft of the Neanderthal genome, the scientists gathered DNA from the fossils of individual Neanderthals that lived in Croatia about 40,000 years ago. The scientists sequenced fragments of DNA totalling more than 4 billion nucleotides. To figure out what spot on which chromosome each fragment belonged, they lined up the Neanderthal DNA against the genomes of humans and chimpanzees. They are far from having a precise read on all 3 billion nucleotides in the Neanderthal genome. But they were able to zero in on many regions of the rough draft and get a much finer picture of interesting genes.
One of the big questions the scientists wanted to tackle was how those interesting genes evolved over the past six million years, since our ancestors split off from the ancestors of chimpanzees. So they compared the Neanderthal genome to the genome of chimpanzees, as well as to humans from different regions of the world, including Africa, Europe, Asia, and New Guinea.
This comparison is tricky because human DNA, like human skulls, is loaded with variations. The DNA of any two people can differ at millions of spots. Those differences may consist of as little a single nucleotide, or a long stretch of duplicated DNA. Each of us picks up a few dozen new mutations when we’re born, but most of the variations in our genome have been circulating in our species for centuries, millennia, and, in some cases, hundreds of thousands of years. Over the course of history these variants have gotten mixed and matched in different human populations. Some of them vary from continent to continent. It’s possible to tell someone from Nigeria from someone from China based on just a couple hundred genetic markers. But a lot of the same variations that Chinese people have also exist in Nigeria. That’s because Chinese people and Nigerians descend from an ancestral population. The gene variants first arose in that ancestral variation and then were all passed down from generation to generation, even as humans migrated and diverged across the planet. And when Paabo and his colleagues looked at the Neanderthal genome, they discovered that Neanderthals carried some of the same variants in their genome too.
The scientists compared the variants in the Neanderthal genome to those in humans to figure out when the two kinds of humans diverged. They estimate that the two populations became distinct between 270,000 and 440,000 years ago. After the split, our own ancestors continued to evolve. It’s possible that genes that evolved after that split helped to make us uniquely human. To identify some of those genes,Pääbo and his colleagues looked for genes that were identical in Neaderthals and chimpanzees, but had undergone a significant change in humans.
They didn’t find many. In one search, they looked for protein-coding genes. Genes give cells instructions for how to assemble amino acids into proteins. Some mutations don’t change the final recipe for a protein, while some do. Pääbo and his colleagues found that just 78 human genes have evolved to make a new kind of protein, differing from the ancestral form by one or more amino acids. (We have, bear in mind, 20,000 protein-coding genes.) Only five genes have more than one altered amino acid.
The scientists also found some potentially important changes in stretched of human DNA that doesn’t encode genes. Some of these non-coding stretches act as switches for neighboring genes. Others encode tiny pieces of single-stranded versions of DNA, called microRNAs. MicroRNAs can act as volume knobs for other genes, boosting or squelching the proteins they make.
Another way to look for uniquely human DNA is to search for stretches of genetic material that still retain the fingerprint of natural selection. In the case of many genes, several variants of the same gene have coexisted for hundreds of thousands of years. Some variants found in living humans also turn up in the Neanderthal genome. But there are some cases in which natural selection has strongly favored humans with one variant of a gene over others. The selection has been so strong sometimes that all the other variants have vanished. Today, living humans all share one successful variant, while the Neanderthal genome contains one that no longer exists in our species. The scientists discovered 212 regions of the human genome that have experienced this so-called “selective sweep.”
You can see the full list of all these promising pieces of DNA in the paper Pääbo and his colleagues published today. If you’re looking for a revelation of what it means to be human, be prepared to be disappointed by a dreary catalog of sterile names like RPTN and GREB1 and OR1K1. You may find yourself with a case of Yet Another Genome Syndrome. In all fairness, the scientists do take a crack at finding meaning in their catalog. They note that a number of evolved genes are active in skin cells. But does that mean that we evolved a new kind of skin color? A new way of sweating? A better ability to heal wounds? At this point, nobody really knows.
If you believe the difference between humans and Neanderthals is primarily in the way we think, then you may be intrigued by the strongly selected genes that have been linked to the brain. These genes got their links to the brain thanks to the mental disorders that they can help produce when they mutate. For exampe, one gene, called AUTS2, gets its name from its link to autism. Another strongly-selected human gene, NRG3, has been linked to schizophrenia. Unfortunately, these disease associations just tell scientists what happens when these genes go awry, not what they do in normal brains.
The most satisfying hypothesis the scientists offer is also the one with the deepest historical resonance. It has to do with the brow ridge that so puzzled Schaafhausen back in 1857. One of the strongly selected genes in humans, known as RUNX2, has been linked to a condition known as cleiodocranial dysplasia. People who suffer from this condition have a bell-shaped rib cage, deformed shoulder bones, and a thick brow ridge. All three traits distinguish Neanderthals from humans.
Pääbo and his colleagues then turned to the debate over what happened when humans emerged from Africa. Scientists have debated for years what happened when our ancestors encountered Neanderthals and other extinct hominin populations. Some have argued that they kept their distance and never interbred. Others have scoffed that any human could show such self-restraint. After all, humans have been known to have sex with all sorts of mammals when given the opportunity, so why should they have been so scrupulous about a very human-like mammal?
The evidence that scientists have gathered up till now has been very confusing. If you just look at mitochondria, for example, all the Neanderthal form tiny twigs on a branch that’s distant from the human branch. If Neanderthals and humans had interbred often enough, then some people today might be carrying mitochondrial DNA that was more like that of Neanderthals than like other humans.
On the other hand, some scientists looking at other genes have found what they claim to be evidence of interbreeding. They would find gene variants in living humans that had evolved from an ancestral gene about a million years ago. One way to explain this pattern was to propose that modern humans interbred with Neanderthals or other hominins. Some of their DNA then entered our gene pool and has survived till today. In one case, a team of scientists proposed that a gene variant called Microcephalin D hopped into our species from Neanderthals and then spread very quickly, driven perhaps by natural selection. Making this hypothesis even more intriguing was the fact that the gene is involved in building the brain.
Pääbo and his colleagues looked for pieces of the Neanderthal genome scattered in the genomes of living humans. The scientists found that on average, the Neanderthal genome is a little more similar to the genomes of people in Europe, China, and New Guinea, than it is to the genomes of people from Africa. After carefully comparing the most similar segments of the genomes, the scientists propose that Neanderthals interbred with the first immigrants out of Africa–perhaps in the Middle East, where the bones of both early humans and Neanderthals have been found.
Today, the people of Europe and Asia have genomes that are 1 to 4 percent Neanderthal.That interbreeding doesn’t seem to have meant much to us, in any biological sense. None of the segments our species picked up from Neanderthals was favored by natural selection. (Microcephalin D turns out to have been nothing special.)
While working on this post, I contacted two experts who have been critical of some earlier studies on hominin interbreeding, Laurence Excoffier of the University of Bern and Nick Barton of the University of Edinburgh. Both scientist gave the Neanderthal genome paper high marks and agree in particular that the interbreeding hypothesis is a good one. But they do think some alternative hypotheses have to be tested. For example, interbreeding is not the only way that some living humans might have ended up with Neanderthal-like pieces of DNA. Cast your mind back 500,000 years, before the populations of humans and Neanderthals had diverged. Imagine that those ancestral Africans were not trading genes freely. Instead imagine that some kind of barrier emerged to keep some gene variants in one part of Africa and other variants in another part.
Now imagine that the ancestors of Neanderthals leave Africa, and then much later the ancestors of Europeans and Asians leave Africa. It’s possible that both sets of immigrants came from the same part of Africa. They might have both taken some gene variants with them did not exist in other parts of Africa. Today, some living Africans still lack those variants. This scenario could lead to Europeans and Asians with Neanderthal-like pieces of DNA without a single hybrid baby ever being born.
If humans and Neanderthals did indeed interbreed, Excoffier thinks there’s huge puzzle to be solved. The new paper suggests that genes flowed from Neanderthals to humans only at some point between 50,000 and 80,000 years ago–before Europeans and Asians diverged. Yet we know that humans and Neanderthals coexisted for another 20,000 years in Europe, and probably about as long in Asia. If humans and Neanderthals interbred during that later period, Excoffier argues, the evidence should be sitting in the genomes of Europeans or Asians. The fact that the evidence is not there means that somehow humans really did find the self-restraint not to mate with Neanderthals.
Because interbreeding involves sex, it dominates the headlines about Pääbo’s research. But I’m left wondering about the Neanderthals themselves. We now have a rough draft of the operating instructions for a kind of human that has been gone from the planet for 28,000 years, which had its own kind of culture, its own way of making its way through the world. Yet I found very little in the paper about what the Neanderthal genome tells us about their owners. It’s wonderful to use the Neanderthal genome as a tool for subtracting away our ancestral DNA and figure out what makes us uniquely human. But it would also be great to know what made Neanderthals uniquely Neanderthal.
[Image from Project Gutenberg]
We’re all a bit of a Neanderthal:
As a result, between 1pc [percent] and 4pc of the DNA of non-African people alive today is Neanderthal, according to the research. The discovery emerged from the first attempt to map the complete Neanderthal genetic code, or genome. It more or less settles a long-standing academic debate over interbreeding between separate branches of the human family tree. Evidence in the past has pointed both ways, for and against modern humans and Neanderthals mixing their genes.
…
Prof Svante Paabo, of the Institute for Evolutionary Anthropology in Leipzig, Germany, said: “Those of us who live outside Africa carry a little Neanderthal DNA in us.”
I will have a thorough write-up when I get a hold of the paper, which should be soon. As I said, this is a story of genomics, not just genetics. 1-4% is not trivial. The Daily Telegraph has more:
They were surprised to find that Neanderthals were more closely related to modern humans from outside Africa than to Africans.
Even more mysteriously, the relationship extended to people from eastern Asia and the western Pacific – even though no Neanderthal remains have been found outside Europe and western Asia.
The most likely explanation is that Neanderthals and Homo sapiens interbred before early modern humans struck out east, taking traces of Neanderthal with them in their genes.
Professor Svante Paabo, director of evolutionary genetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who led the international project, said: “Since we see this pattern in all people outside Africa, not just the region where Neanderthals existed, we speculate that this happened in some population of modern humans that then became the ancestors of all present-day non-Africans.
“The most plausible region is in the Middle East, where the first modern humans appeared before 100,000 years ago and where there were Neanderthals until at least 60,000 years ago.
“Modern humans that came out of Africa to colonise the rest of the world had to pass through that region.”
…
Several genes were discovered that differed between Neanderthals and Homo sapiens and may have played important roles in the evolution of modern humans.
They included genes involved in mental functions, metabolism, and development of the skull, collar bone and rib cage.
Image Credit: United Press International
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