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July 3, 2012

Evolution, not ecology

Filed under: Ecology,Environment,Environmentalism — Razib Khan @ 9:59 pm

One of my major gripes with my friends in ecology is that there is a tendency to look at every problem through the lens of ecological models. Garrett Hardin, who popularized the term “tragedy of the commons” is an exemplar of this. People in ecology often get irritated by the public confusion between it, a positive scientific discipline, and environmentalism, a normative set of beliefs (it doesn’t help when some environmentalist groups have names like “ecology movement”). But the fact is there are deep commonalities in terms of prior assumptions by both ecologists and environmentalists. Despite evolutionary ecology, the reality is that ecologists seem to be characterized by a mindset which posits limits to growth and a finite set of responses to the challenges of scarce resources. That is, the Malthusian paradigm.

I bring this up because despite the similarities between ecology and economics it strikes me that ecologists often have a difficult time admitting that the parameters of the model which they think they have a good grasp of may not always be fixed. Incentives and innovation can shift the dynamics radically. Consider George Monbiot’s about ...

February 20, 2012

Money vs. Science

Filed under: Environment,Science and Politics,Top Posts — Sean Carroll @ 4:35 pm

Everyone who has been paying attention knows that there is a strong anti-science movement in this country — driven partly by populist anti-intellectualism, but increasingly by corporate interests that just don’t like what science has to say. It’s an old problem — tobacco companies succeeded for years in sowing doubt about the health effects of smoking — but it’s become significantly worse in recent years.

Nina Fedoroff is the president of the American Association for the Advancement of Science (AAAS), which is holding its annual meeting right now. She is not holding back about the problem, but tackling it directly. From a weekend article in the Guardian (h/t Dan Gillmor):

“We are sliding back into a dark era,” she said. “And there seems little we can do about it. I am profoundly depressed at just how difficult it has become merely to get a realistic conversation started on issues such as climate change or genetically modified organisms.”

Tim F. at Balloon Juice points to this flowchart at Climate Progress that illustrates how the money and message gets sent around to sow doubt about scientific findings. (Okay, it’s not really a flow chart, but you get the point.) I was also struck by a link to an older article by Ian Sample, which put the problem in its starkest terms: the American Enterprise Institute was offering $10,000 to scientists and economists who were willing to write op-eds or essays critiquing the IPCC climate report — before it was published. Money goes a long way.

Relatedly, here’s Ruth Bader Ginsburg trying to push the Supreme Court away from its ruling in Citizens United, the notorious case that led to the creation of SuperPACs by deciding that corporations were persons, and not letting them advertise anonymously would be a grievous violation of their free-speech rights. We’ll see how well she does. Scientists, meanwhile, need to keep speaking out about the integrity of our field. When researchers are attacked and their jobs threatened by politicians who disagree with their results, it’s time to stand up for what science really means.


January 14, 2012

The old Amazon

Filed under: Agriculture,Amazon,Anthroplogy,Charles C. Mann,Environment — Razib Khan @ 2:49 pm

Once Hidden by Forest, Carvings in Land Attest to Amazon’s Lost World:

For some scholars of human history in Amazonia, the geoglyphs in the Brazilian state of Acre and other archaeological sites suggest that the forests of the western Amazon, previously considered uninhabitable for sophisticated societies partly because of the quality of their soils, may not have been as “Edenic” as some environmentalists contend.

Instead of being pristine forests, barely inhabited by people, parts of the Amazon may have been home for centuries to large populations numbering well into the thousands and living in dozens of towns connected by road networks, explains the American writer Charles C. Mann. In fact, according to Mr. Mann, the British explorer Percy Fawcett vanished on his 1925 quest to find the lost “City of Z” in the Xingu, one area with such urban settlements.

In addition to parts of the Amazon being “much more thickly populated than previously thought,” Mr. Mann, the author of “1491,” a groundbreaking book about the Americas before the arrival of Columbus, said, “these people purposefully modified their environment in long-lasting ways.”

If one wants to recreate pre-Columbian Amazonia, most of the forest needs to be removed, with many people and a managed, highly productive landscape replacing it,” said William Woods, a geographer at the University of Kansas who is part of a team studying the Acre geoglyphs.

“I know that this will not sit well with ardent environmentalists,” Mr. Woods said, “but what else can one say?”


There are two descriptive models which have to be interpreted in different normative frames. First, there is the model whereby before the arrival of the Europeans the New World was lightly populated by indigenous groups which had a minimal impact upon the environment. This is the description. Before the 1960s this was viewed by the mainstream culture as a rationale for the justified conquest of the New World by Europeans, who put the land to productive economic usage, whereas before it had been fallow and under-untilized. After the 1960s many, especially in the environmental movement, inverted the moral valence of the description. Instead of being primitive savages, the native peoples were at balance with the environment. Rather than an outmoded way of life to be superseded, they were a potential model for the future.

The second descriptive model is the one that Charles C. Mann outlines in 1491: New Revelations of the Americas Before Columbus. It posits that in fact the New World was much more heavily populated and its environment more impacted by humanity than we had thought previously. Rather, it suggests that the introduction of Old World diseases resulted in massive population crashes, subsequent to which there was a “re-wilding” of much of the Americas. Mann focuses more on the period before the arrival of Europeans, but if you read the scholarship on the arrival of Paleo-Indians there is a fair amount of evidence that even their appearance resulted in a massive change in the suite of fauna which characterized the New World (e.g., the gray wolf and American bison are also Holocene newcomers, just like man).

Some have argued tat Mann has taken a maximalist position (in fact, some readers have lied and stated that Mann argued that the Amazon was as populated as Bangladesh!). But even granting that Mann may be sampling from the more revisionist tail of the scholarship, I think it is creditable that we need to move away from the extreme position of the first descriptive model. There is a fair amount of circumstantial evidence that New World civilizations had not attained the same level of sophistication and complexity as Old World civilizations (see Guns, Germs, and Steel for some of the reasons why). But it is also likely that the Aztecs and Incas were not sui generis aberrations, but rather one point along the spectrum of social complexity which characterized the New World.

This is a subtle point though, because the new model also has normative ramifications. I state above that New World civilizations were not as complex or developed as Old World ones, and that is not a position that many are comfortable with. Rather, they may want to assert that the New World societies were just as complex and sophisticated as the Old World civilizations, that fundamentally all civilizations have equal value and similar character. Therefore, these partisans are particularly enthusiastic about the model which Charles C. Mann popularizes in 1491, as it reverses the narrative of noble simple savages, projecting the indigenous as highly cultured, and only brought down by the biological weapons which Europeans brought.

Where does that put those who wish to construct a plausible model of reality, rather than a mythic history for purposes of ideology? It is lazy to simply pick the position in the middle, but in this case that’s probably the most prudent unless you want to dive into the primary literature yourself. I don’t accept the old model anymore for a variety of reasons, not just having to do with the natural history of the New World. But, I can’t personally assess in detail the magnitude of the numbers that some of the scholars Mann relies upon to revise upward population estimates. So I take the revision with a grain of salt and some caution.

I would conclude that there is one reason I can think of why the Amazon basin might have been more suitable for human habitation that some other wet tropical zones in the Old World: the relative lack of disease. Many wet lowland zones which would otherwise be suitable farmland are lightly populated due to malaria, but this was not an issue in the New World before 1492.

January 10, 2012

Noisy Systems and Wandering Canines

Filed under: Environment,Science and Society — Sean Carroll @ 4:03 pm

There are three types of scientific explanations: those involving cats, those involving dogs, and those that aren’t very interesting. Via Andrew Revkin, here’s a well-done animation that uses a dog to explain the difference between a long-term trend and a short-term variation.

Show this to your local climate denialist when they get confused about the distinction between “climate” and “weather.” Not that it will change their minds, but the dog is cute.


July 30, 2011

A world full of children

Filed under: Agriculture,Culture,Environment,Neolithic,Neolithic Revolution — Razib Khan @ 11:07 pm

The figure to the left is from a new paper in Science, When the World’s Population Took Off: The Springboard of the Neolithic Demographic Transition. It reports the findings from 133 cemeteries in the northern hemisphere in regards to the proportion of 5-19 year old individuals. When calibrated to period when agriculture was introduced into a specific region there seems to be a clear alignment in terms of a demographic transition toward a “youth bulge.” Why? A standard model of land surplus explains part of it surely. When farmers settle “virgin land” there is often a rapid “catch up” phase toward the Malthusian limit, the carrying capacity. Another possibility though is that sedentary populations did not need to space their offspring nearly as much as mobile hunter-gatherers. Whatever the details, the facts remain that the data do point to a shift in the age pyramid during this period. The author wonders as to the possible cultural implications of this. There is an a priori assumption that a young vs. old age profile in a society constrains its choices and channels its energies (e.g., think the “baby boom” generation in ...

June 8, 2011

Through the lens of a glass house

Filed under: Environment,Invasive Species — Razib Khan @ 12:15 pm

Nature has a very interesting piece up right now, Don’t judge species on their origins, which addresses the periodic bouts of hysteria which are triggered by ‘invasive species.’ I’ve addressed before the issue of biological terminology of convenience being transformed into fundamental and principled Truths. The separation between ‘artificial’ and ‘natural’ selection, or more archaically the division between ‘humankind’ and the ‘natural world.’ There are important reasons why these terms emerged the way they did, but we shouldn’t confuse the terminology for the truth. This seems definitely a problem when we humans talk about ‘invasive’ and ‘non-native’ species, as well as whether population X is worth being protected because it is a ‘species’ according to a genetic definition, or whether it is too ‘genetically polluted.’ We are after all an invasive species ourself!

Since the piece is behind a paywall I’ll extract the most relevant paragraphs:

Today’s management approaches must recognize that the natural systems of the past are changing forever thanks to drivers such as climate change, nitrogen eutrophication, increased urbanization and other land-use changes. It is time for scientists, land managers and policy-makers to ditch this preoccupation with the native–alien dichotomy and embrace more dynamic and pragmatic approaches ...

May 5, 2011

Why the Amazon Rainforest is species rich

Filed under: Amazon Rainforest,Amazonia,Diversity,Ecology,Environment,Speciation — Razib Khan @ 3:08 pm


A monkey frog

The Pith: The Amazon Rainforest has a lot of species because it’s been around for a very long time.

I really don’t know much about ecology, alas. So my understanding of evolution framed in its proper ecological context is a touch on the coarse side. When I say I don’t know much about ecology, I mean that I lack a thick network of descriptive detail. So that means that I have some rather simple models in my head, which upon closer inspection turn out to be false in many specific instances. That’s what you get for relying on theory. Today I ran into a paper which presented me with some mildly surprising results.

The question: why is the Amazon Rainforest characterized by such a diversity of species? If you’d asked me that question 1 hour ago I would have said that it was a matter of physics. That is, the physical parameters of a high but consistent rainfall and temperature regime. This means the basic energetic inputs into the biome is high, and its consistency allows the organisms to plan their life schedule efficiently, maximizing the inputs. All ...

March 24, 2011

Nuclear power as the “shark attacks” of energy

Filed under: Energy,Environment,Environmentalism,Futurism,Nuclear Power — Razib Khan @ 10:03 am



Image Credit: Stefan Kuhn

I was at a coffee shop recently and a SWPL couple (woman had dreads to boot!) a number of tables away were reading a newspaper, and the husband expressed worry about the Fukushima disaster. The wife responded that “now other people will understand how dangerous nuclear power is,” with a sage nod. They then launched into twenty minutes of loud righteous gibberish about chemicals (I had a hard time making sense of it, despite the fact that I learned a lot about chemicals in the past due to my biochemistry background). Because they’d irritated me I was curious and I tailed them as they left. Naturally they had driven to get coffee in a S.U.V. of some sort (albeit, a modestly sized one which looked like it was more outfitted for the outdoors’ activities common in the Pacific Northwest; they’d probably done their cost vs. benefit about those chemicals!).

In terms of radiation fears, I suspect that if more people just automatically knew the inverse-square law in relation to the drop off of its effects we’d be in a whole lot less ...

October 11, 2010

Natural selection in our time

Filed under: Adaptation,Biology,Environment,Evolution,Genetics,Selection — Razib Khan @ 12:35 am

Last month in Nature Reviews Genetics there was a paper, Measuring selection in contemporary human populations, which reviewed data from various surveys in an attempt to adduce the current trajectory of human evolution. The review didn’t find anything revolutionary, but it was interesting to see where we’re at. If you read this weblog you probably accept a priori that it’s highly unlikely that evolution “has stopped” because infant mortality has declined sharply across developed, and developing, nations. Evolution understood as change in gene frequencies will continue because there will be sample variance in the proportions of given alleles from generation to generation. But more interestingly adaptive evolution driven by change in mean values of heritable phenotypes through natural selection will also continue, assuming:

1) There is variance in reproductive fitness

2) That that variance is correlated with a phenotype

3) That those phenotypes are at all heritable. In other words, phenotypic variation tracks genotypic variation

Obviously there is variance in reproductive fitness. Additionally, most people have the intuition that particular traits are correlated with fecundity, whether it be social-cultural identities, or personality characteristics. The main issue is probably #3. It is a robust finding for example that in developed societies the religious tend to have more children than the irreligious. If there is an innate predisposition to religiosity, and there is some research which suggests modest heritability, then all things being equal the population would presumably be shifting toward greater innate predisposition toward religion as time passes. I do believe religiosity is heritable to some extent. More precisely I think there are particular psychological traits which make supernatural claims more plausible for some than others, and, those traits themselves are partially determined by biology. But obviously even if we think that religious inclination is partially heritable in a biological sense, it is also heritable in the familial sense of values passed from one generation to the next, and in a broader cultural context of norms imposed from on high. In other words, when it comes to these sorts of phenotypic analyses we shouldn’t get too carried away with clean genetic logics. In Shall the Religious Inherit the Earth? Eric Kaufmann notes that it is in the most secular nations that the fertility gap between the religious and irreligious is greatest, and therefore selection for religiosity would be strongest in nations such as Sweden, not Saudi Arabia. But as a practical matter biologically driven shifts in trait value in this case pales in comparison to the effect of strong cultural norms for religiosity.

Below are two of the topline tables which show the traits which are currently subject to natural selection. A + sign indicates that there is natural selection for higher values of the trait, and a – sign the inverse.  An s indicates stabilizing selection, which tells you that median values have higher fitnesses than the extremes. The number of stars is proportional to statistical significance.


future1

future2

Some of this is not surprising. The age of the onset of menarche has been dropping in much of the world. I suspect this is mostly due to better nutrition, but a consequence of this shift is earlier fertility for some females. The authors are nervous about the robust correlation of higher fertility with lower intelligence, but notice that the pattern for wealth and income is different and more complicated. The key is to look at education.  Whether you believe intelligence exists or not in any substantive concrete sense, those who are more intelligent are more likely to have had more education, and there’s a rather common sense reason why investing in more schooling would reduce your fertility: you simply forgo some of your peak reproductive years, especially if you’re female. The higher you go up the educational ladder the stronger the anti-natalist cultural and practical pressures become (the latter is a heavier burden for females because of their biological centrality in child-bearing, but both males and females are subject to the former). As with religion even if the differences have no biological implication because you believe the correlations are spurious or reject the existence of the trait one presumes that parents and subcultures pass on values to offspring. If higher education has anti-natalist correlations we shouldn’t be surprised if subsequent generations turn away from higher education. Their parents were the ones who were more likely to avoid it.

We live in interesting times.

August 24, 2010

Decline in forest cover

Filed under: Environment,Forests — Razib Khan @ 11:29 am

I’ve spent most of my life in relatively forested areas, and took forestry courses in secondary school (which is why I can still distinguish doug fir from spruce by looking at the needles). In my youth I even had friends who were loggers during the summer. But I haven’t taken a deep scientific interest in forests for a long time. So I decided to look at the Google public data set to get a sense of long term trends.

As you can see, there hasn’t been much of an aggregate decline in forests. How about the nations with a lot of forest cover?


I was surprised that the slopes didn’t have a stronger negative value. What about you? If this is your area of expertise, what’s going on? Are we trading climax ecosystems for second growth and lumber plantations? I was surprised that the USA had nearly as much forest cover as Canada, but I guess a lot of the Great White North is tundra.

Also, removing Russia to make the scale easier, and adding China and India, you can see the impact of the recent Chinese reforestation drive pretty clearly:

June 21, 2010

Animal Apartheid

Filed under: Environment,Environmentalism,Ethics,Nature — Razib Khan @ 6:46 am

Here’s an article from Canada on the debate about whether hybridization should be discouraged. I understand the impulse toward preserving nature as it is, but the drive for presumed purity seems almost fetishistic. Consider this sentence: ” Or could hybrids actually weaken genetically pure populations of disappearing wildlife?” What does “genetically pure” mean in a deep sense here? We know what it means instrumentally for the purposes of conservation genetics, but the way people talk about pristine lineages makes it seem an almost ethical concern.


When it comes to conservation and environmental policy you’re at the intersection of science, norms, and the messy world of human possibility. Perspective matters a lot in how you value or weight the parameters within your value system. To me the preservation of putatively pure lineages immemorial smacks a bit of pre-Darwinian biology, with its focus on systematic analysis of fixed and eternal kinds as well as a descriptive analysis of anatomy and physiology. At the other end is evolutionary biology which is a process, a phenomenon, understood as a flux of gene frequencies and morphs over time. It is by definition a refutation of a static conception of nature. Of course it takes time…but but not that much time. And then there’s the tendency to see humans as apart and beyond nature, exogenous to the system, destabilizing an eternal equilibrium. This is also arguably a false ideal, humans have been part of the ecosystem of every continent excepting Antarctica for at least 10,000 years, Australia for 50,000 years, Eurasia for a million years, and Africa somewhat longer. Modern H. sapiens sapiens has likely reshaped whole ecosystems through predation and fire even before agriculture and dense societies.

Let’s have a more nuanced and subtle conversion here, and put the focus on what our ultimate values are, or at least the ultimate values of the majority. As it is too often it seems to me that we’re not that far from “king’s wood” whereby we view nature as something to be isolated from the common man, who by his presence sullies and contaminates its purity. And now the fixation on distinct kinds and lineages seems to veer in a similar direction, albeit focusing on the purity of species and sub-species rather than nature as a whole.

May 4, 2010

The dynamism of nature

Filed under: Biodiversity,Ecology,Environment — Razib Khan @ 12:06 am

On this week’s ResearchBlogCast we discussed Adaptation, Plasticity, and Extinction in a Changing Environment: Towards a Predictive Theory (see my post reviewing it). The basic idea was to discuss a simple mathematical model which treated biological populations as something more than simply static constants buffeted by changes in physical parameters. In particular there’s often an implicit model that species exist at a particular and precise equipoise with an environment, and that when those environmental parameters are shifted that the species is in jeopardy unless it can track its optimal environment through migration.

In some ways this would be mighty convenient for us if it were so. If species were static we wouldn’t have to worry about weeds becoming resistant to pesticide, or diseases wrecking havoc to our crops, and so forth. But biology is dynamic, both on the life history and evolutionary scale. I think it would benefit us to take this into account when we humans consider the value we place on conservation, and the decisions we make to maintain biodiversity. Kevin Zelnio pointed out that there have been worries about the disappearance of charismatic fauna for about a generation now, and though species such as the tiger and elephant are still endangered (and because of their relatively long generation times this is problematic), many species which we were told as children would become extinct by the time we were adults remain a presence today in the wild. Some of this is surely due to conservation after the awareness of the threats, but another issue may be that some of these species are more resilient than we think, or give them credit for. Dave Munger reminded us that in 2007 100,000 Lowland Gorillas “discovered”, tripling the numbers of the species immediately. One way of looking at it is that these gorillas were mighty lucky that they’d been unnoticed…but another issue may be that gorillas coevoled to some extent with hominids and may have some sense where to go to avoid human habitation.

This is not to recommend complacency. And I haven’t even broached the serious normative issues as to the value of biodiversity outside of its human utilitarian consequences. These are points over which reasonable people can discuss and differ. Rather, when we speak of the environmental and non-human life we often speak as if humanity and physical nature are the two active forces operative on a passive and static biological nature. This is obviously not true. Our species’ mastery of the physical sciences in the past 200 years has given us a sense of power over the biological world, but we shouldn’t get complacent, and we shouldn’t dismiss the resilience and cleverness of nature, though that resilience and cleverness does not always redound to our benefit.

March 29, 2010

Thomas Malthus was right. Mostly

pleistocene_brain_sizeJohn Hawks has an excellent post rebutting some misinformation and confusion on the part of Colin Blakemore, an Oxford neurobiologist. Blakemore asserts that:

* There was a sharp spike in cranial capacity ~200,000 years ago, on the order of 30%

* And, that the large brain was not deleterious despite its large caloric footprint (25% of our calories service the brain) because the “environment of early humans was so clement and rich in resources”

Hawks refutes the first by simply reposting the chart the above (x axis = years before present, y axis = cranial capacity). It’s rather straightforward, I don’t know the paleoanthropology with any great depth, but the gradual rise in hominin cranial capacity has always been a “mystery” waiting to be solved (see Grooming, Gossip, and the Evolution of Language and The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature). Blakemore may have new data, but as they say, “bring it.” Until then the consensus is what it is (the hominins with the greatest cranial capacities for what it’s worth were Neandertals, and even anatomically modern humans have tended toward smaller cranial capacities since the end of the last Ice Age along with a general trend toward smaller size).


But the second issue is particularly confusing, as Blakemore should have taken an ecology course at some point in his eduction if he’s a biologist (though perhaps not). One of the problems that I often have with biologists is that they are exceedingly Malthusian in their thinking, and so have a difficult time internalizing  the contemporary realities of post-Malthusian economics (see Knowledge and the Wealth of Nations: A Story of Economic Discovery).Innovation and economic growth combined with declining population growth have changed the game in fundamental ways. And yet still the biological predisposition to think in Malthusian terms is correct for our species for almost its whole history.*

A “tropical paradise” is only a tropical paradise if you have a modicum of affluence, leisure, and, modern medicine. Easter Island is to a great extent a reductio ad absurdum of pre-modern man and gifted with a clement regime. Easter Island’s weather is mild, the monthly low is 18/65 °C/°F and the monthly high is 28/82 °C/°F. The rainfall is 1,118/44 mm/in. But constrained on an island the original Polynesians famously transformed it into a Malthusian case-study. We literally breed up to the limits of growth, squeezing ourselves against the margins of subsistence.

I can think of only one way in which Blakemore’s thesis that the environment of early humans was rich in resources might hold, at least on a per capita basis: the anatomically modern humans of Africa exhibited bourgeois values and had low time preference. In other words, their population was always kept below ecological carrying capacity through forethought and social planning, since there is no evidence for much technological innovation which would have resulted in economic growth to generate surplus. My main qualm with this thesis is that it seems to put the cart before the horse, since one presupposes that a robust modern cognitive capacity is usually necessary for this sort of behavior.

* Malthus’ biggest mistake was probably that he did not anticipate the demographic transition, whereby gains in economic growth were not absorbed by gains in population.

February 24, 2010

Be safe and live long

Filed under: Environment — Gene Expression @ 10:57 pm

Arboreality has allowed for the evolution of increased longevity in mammals:

The evolutionary theory of aging predicts that species will experience delayed senescence and increased longevity when rates of extrinsic mortality are reduced. It has long been recognized that birds and bats are characterized by lower rates of extrinsic mortality and greater longevities than nonvolant endotherms, presumably because flight reduces exposure to terrestrial predators, disease, and environmental hazards. Like flight, arboreality may act to reduce extrinsic mortality, delay senescence, and increase longevity and has been suggested as an explanation for the long lifespans of primates. However, this hypothesis has yet to be tested in mammals in general. We analyze a large dataset of mammalian longevity records to test whether arboreal mammals are characterized by greater longevities than terrestrial mammals. Here, we show that arboreal mammals are longer lived than terrestrial mammals at common body sizes, independent of phylogeny. Subclade analyses demonstrate that this trend holds true in nearly every mammalian subgroup, with two notable exceptions--metatherians (marsupials) and euarchontans (primates and their close relatives). These subgroups are unique in that each has experienced a long and persistent arboreal evolutionary history, with subsequent transitions to terrestriality occurring multiple times within each group. In all other clades examined, terrestriality appears to be the primitive condition, and species that become arboreal tend to experience increased longevity, often independently in multiple lineages within each clade. Adoption of an arboreal lifestyle may have allowed for increased longevity in these lineages and in primates in general. Overall, these results confirm the fundamental predictions of the evolutionary theory of aging.

The same logic probably explains the long lifespans of tortises. Until humans showed up their shells were pretty good at insulating them from the risks of predation.

Citation: Milena R. Shattuck and Scott A. Williams, Arboreality has allowed for the evolution of increased longevity in mammals, doi:10.1073/pnas.0911439107

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