Archive for the 'General Science' Category

Mar 10 2020

Day Was Shorter 70 Million Years Ago

What does an extinct mollusk have to do with the Moon? This is one of those amazing science stories that ties together multiple disciplines and lines of evidence into one elegant narrative. In this case a detailed analysis of a 70 million year old mollusk shell has given scientists a critical piece of information that will help them model the Earth-Moon system.

Let’s start with the Moon – astronomers know that the Moon is moving farther away from the Earth at a constant rate, 3.82 centimeters per year. We can precisely measure this because the Apollo missions left corner reflectors on the surface of the Moon, and we can shoot lasers off those reflectors and measure the round-trip travel time. Because scientists have also precisely measured the speed of light, we can use this round-trip time to calculate the exact distance between the laser on Earth and the reflector on the Moon.

Why is the Moon moving away from the Earth? In a word – tides. Tidal forces from nearby large objects causes a bulge to form. We are most familiar with this phenomenon because of the bulge in the ocean caused mostly by the Moon (and to a lesser degree the Sun) which we experience locally as a rising and falling of the sea. The tidal bulge on the Earth is slightly ahead of the Moon in its orbit, because the Earth is spinning faster than the Moon. This leading bulge tugs slightly on the Moon, accelerating it into a higher orbit farther from the Earth. This represents a transfer of momentum from the Earth to the Moon via gravity, which not only moves the Moon farther away, but slows down the rotation of the Earth (and the conservation of angular momentum is obeyed).

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Mar 02 2020

A Claim for Dinosaur Proteins and DNA

Another paper has been published in the simmering controversy over whether or not proteins, and even DNA, can survive millions of years in well-preserved dinosaur (non-avian dinosaurs, that is) fossils. The paper looks at cartilage from a duck-billed dinosaur, a young Hypacrosaurus stebingeri. The authors claim:

“…microstructures morphologically consistent with nuclei and chromosomes in cells within calcified cartilage. We hypothesized that this exceptional cellular preservation extended to the molecular level and had molecular features in common with extant avian cartilage. Histochemical and immunological evidence supports in situ preservation of extracellular matrix components found in extant cartilage, including glycosaminoglycans and collagen type II. Furthermore, isolated Hypacrosaurus chondrocytes react positively with two DNA intercalating stains.”

Let me say right away that these claims are controversial, but what would they mean if true? If we could examine the structure of proteins and DNA from >65 million years ago, in well-preserved dinosaur fossils, then the world of molecular biology would extend back to that era. Molecular examination has had a significant impact on paleontology – but it has limits. So far the oldest DNA sequenced from a fossil is from a 700,000 year old horse frozen in ice. The oldest protein so far confirmed is from a rhino 1.7 million years old. This means that if the current claims are true, DNA can survive in fossils 100 times longer than the current record would indicate.

This is also not the only source of information from which to estimate the lifespan of DNA. Researchers have examined DNA from Moa specimens in New Zealand, over a span of about 8,000 years. This allowed them to estimate the half-life of DNA, the time over which about half the bonds would be broken. Their estimate – 521 years. This means that all the chemical bonds in a DNA molecule would be gone after 6.8 million years, but having any fragments along enough to sequence would be gone after about one million years. This aligns nicely with the evidence from actual fossils. So claiming DNA from >65 million years would be extraordinary, to say the least. This is why most scientists remain skeptical of these claims.

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Jan 23 2020

Asteroid Not Volcanism Killed the Dinosaurs

Published by under General Science

The popular belief is that an asteroid impact caused the mass extinction at the K-Pg (formerly K-T) boundary 66 million years ago. This is the mass extinction that killed off the non-avian dinosaurs along with 75% of species on Earth. However, in reality there is a raging scientific debate about the exact causes of the extinction event. The two contenders are the asteroid impact, which we know happened right at that time, and extreme volcanism at the Deccan traps in what is now India.

Scientists fall along a spectrum in this debate. At one end there are those who believe the asteroid was the main event, and the volcanic eruptions played little to no role. At the other end are those who believe that climate change caused by the volcanoes, with both global warming from the CO2 and acidification of the oceans, was the main driver of extinction. The asteroid impact, at most, was the coup de grace. In between are those who feel that both events were important to extinction to varying degrees, and we’re just trying to sort out their relative contributions.

The evidence has gone back and forth on this debate, although I think it has been strongly favoring the asteroid impact as the dominant factor. A new study contributes to this debate, and heavily favors the asteroid impact. In fact, the authors argue that their evidence suggests the volcanism at the Deccan traps played no role at all in the extinction. The modeled the outgassing from the Deccan traps and compared the models with the evidence to see which one fit the best. This is what they found:

We found support for major outgassing beginning and ending distinctly before the impact, with only the impact coinciding with mass extinction and biologically amplified carbon cycle change. Our models show that these extinction-related carbon cycle changes would have allowed the ocean to absorb massive amounts of carbon dioxide, thus limiting the global warming otherwise expected from postextinction volcanism.

Essentially the outgassing from the Deccan traps started, according to their model that best fits the evidence, 350,000-200,000 years prior to the impact and extinction. This caused a global warming event of about 2 C, which further lead to a migration of many species toward the poles. However, the outgassing and warming stopped prior to the extinction, the Earth cooled back to its prior baseline, and the various species returned to their previous locations. So the ecosystem has returned to its prior baseline, without any mass extinction, and then the asteroid hit and caused the mass extinction all by itself.

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Jan 14 2020

Communicating The Consensus

Published by under General Science

Science communication is an evolving art, backed by some interesting research. However, my overall take on the state of the research is that it is mostly telling us the various ways in which we fail, rather than how to succeed. The latest target if scicomm handwringing is “consensus messaging.” How do we, and should we, communicate the scientific consensus to the public?

This issue is probably most salient to communication about global warming. Those who deny the scientific consensus on AGW frequently deny that there is a consensus and/or deny that a scientific consensus is even meaningful. How should we address this situation. In 2018 Russil argued that consensus messaging is generally ineffective. Instead we should focus on the victims of climate change:

“If we recognize that climate change danger will be mediated by questions of migration, dislocation and refuge, and if climate change communication abandons the legacy of consensus messaging to involve those affected by danger, how might our work unfold differently?”

It’s fine to try new approaches, but my problem with this argument is that essentially nothing works when it comes to changing minds on AGW, and so the fact that any one strategy does not work doesn’t really tell us anything about that strategy, or favor any other.

The concept of consensus does, in fact, exist in science. I wrote about it previously here and here. If the vast majority of scientists agree on some scientific conclusion, that is a consensus. That much is historically undeniable, so the strategy is often to switch to the position that a consensus is meaningless. That’s not how science works. To bolster this position often an example of when a scientific consensus was wrong is brought up. These examples, however, never work to establish the anti-consensus position.

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Dec 30 2019

A Climate Change Lost Decade

Published by under General Science

It’s fun and interesting to look back over the last decade and think about what has happened and how far we have come. Round years are arbitrary, but it’s a sufficient trigger to take stock and hopefully gain some perspective on the medium course of history. There is a lot to say about the 2010s, and I may take the opportunity to say more, but I want to discuss in this essay what is perhaps our greatest challenge and disappointment over the last decade. In many ways this has been a lost decade for climate change mitigation.

Over the last decade the scientific evidence (and resulting consensus) that the planet is warming, that humans are the primary driver of this trend, and that the consequences are not likely to be good, has only become greater. The last five years have been the hottest five years on record, and this has been the case for most of the last decade. The year 2016 was the hottest, because it was an El Niño year (short term fluctuations will still be overlaid on top of the longer term trend) but the trend is unmistakable. The story of the world’s ice is more complex, with greater regional and year-to-year variations, but total global ice has been decreasing, and if anything accelerated over the last decade. The Greenland ice sheet in particular experienced accelerated melting. As a result there is a real and growing scientific consensus, north of 97% among relevant scientists, that anthropogenic climate change is happening.

We are also experiencing more extreme weather events. We are seeing more droughts, fires, heat waves, and more powerful storms. In the last decade it become clear that, while the worst consequences of climate change are decades and even centuries in the future, we are starting to see real consequences now.

Economists have started to weigh in as well. Numerous studies were published over the last decade, concluding that – climate change will cost the world many billions of dollars and will reduce economic growth, costing even more. Further, the option of allowing climate change to happen and adapting to the results will likely be the costliest option. In addition to the monetary cost, there is a quality of life cost. Extreme weather causes displacement, psychological trauma, and social upheaval. If you think we are having a refugee crisis now, just wait as flooding increasing and more locations become essentially uninhabitable.

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Dec 19 2019

Sequestered Life

Published by under General Science

Researchers may (and I emphasize “may”) have found life in isolated underground pockets of water in South African mines.  What makes this potential find interesting is that this water has been isolated for about 2 billion years. Scanning electron microscopes have found what researchers believe may be a dividing bacterium. If this is confirmed it will be an exciting discovery for a few reasons.

But first – what do we know now? The water was collected from isolated pockets underground. The water is about 7 times as salty as sea water and can get up to about 54 degrees C. This is right at the limit for known extremophiles, but it is possible for bacteria or archaea to exist in these conditions. The evidence for possible life comes mainly from the microscopic images, which are suggestive but not definitive. One of the researchers, Devan Nisson, a graduate student, noted that “It’s possible the shapes were minerals.”

This would not be the first time that geological structures were confused for life. In 1996 researchers famously announced possible signs of life in a meteorite from Mars. Over 20 years later that claim is still not generally accepted. While there remains some controversy, the consensus is that the tiny structures are minerals, not microbes.

Making the claims for life in the South African mines at least plausible is the fact that there are nitrates and sulfates in the water, which could potentially be used by microbes as an energy source. There are abundant small organic acids, which could serve as building blocks and nutrients. So while extreme, it is possible that this water could support life.

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Oct 28 2019

The Golden Rice Saga

Published by under General Science

Science Writer Ed Regis has recently published a book, Golden Rice: The Imperiled Birth of a GMO Superfood, in which he tells the tragic story of golden rice. In his telling he does not come off as an ideologue, or someone who kept with an initial dramatic narrative regardless of the facts. Rather, he wished to find the truth, which is often messy and nuanced.

Golden rice is a genetically modified form of rice that is enriched with beta carotene, the precursor to vitamin A. It was developed by a non-profit humanitarian collaborative, is free of patents, and was produced with the intention of making it freely available to farmers in developing worlds. The first version of golden rice was produced in 2002, but this version had very low beta carotene levels. The latest versions, however, have sufficient levels that if current diets containing rice as the staple source of calories were switched to golden rice, it would be enough to avoid vitamin A deficiency.

Vitamin A deficiency is a global pandemic. According to the WHO:

An estimated 250 000 to 500 000 vitamin A-deficient children become blind every year, half of them dying within 12 months of losing their sight.

Golden rice has the potential to significantly reduce this disease burden by fortifying a daily staple with beta carotene. This sounds like a solid win for science, so what turns this into a tragic tale? Of course you know the answer, irrational resistance based on misplaced fears.

Greenpeace has lead the charge against the development and adoption of golden rice, mainly out of their generic resistance to all things GMO. Regis writes:

Over the years since the prototype version was announced, Greenpeace had issued a practically endless stream of press releases, position papers, and miscellaneous other statements about Golden Rice that were filled with factual inaccuracies, distortions, and wild exaggerations of the truth.

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Oct 24 2019

Another Damning Organic Study

Published by under General Science

A recent study looks at the carbon emission impact if England and Wales switched entirely over to organic farming. They found:

We predict major shortfalls in production of most agricultural products against a conventional baseline. Direct GHG emissions are reduced with organic farming, but when increased overseas land use to compensate for shortfalls in domestic supply are factored in, net emissions are greater. Enhanced soil carbon sequestration could offset only a small part of the higher overseas emissions.

In their model organic farming did not use fossil-fuel based fertilizer. The nitrogen comes from natural sources, like manure, and also rotation crops that fix nitrogen, such as legumes. This does result in a direct reduction in green-house gas (GHG) emissions, but also results in about a 40% decrease in crop production. That shortfall would have to be made up with increased imports, mostly from Europe. So then we have to calculate what it would take to replace the shortfall in production. This is where there is some variability in the model, because it depends exactly what land is converted to crop production. In the most likely scenarios there would be a net increase in GHG emissions of about 20%.

This is a great example of the law of unintended consequences. When dealing with any complex network, like agriculture, you have to consider the effects of any one change on the overall system. This is not the first study to show that organic farming is a net negative for the environment, and so it is in line with previous research. Further, the disadvantages of organic farming get worse as you try to scale it up.

For example, consider the nitrogen cycle – agriculture is largely a system of recycling nitrogen into food. So for any system you have to consider where all the nitrogen is coming from. Organic farming uses manure, but when the world’s agriculture was limited to manure as a source of nitrogen, that severely limited food production. The green revolution was largely created by the ability to make artificial fertilizer and therefore a non-manure based source of nitrogen. Bottom line – we cannot support the world’s population on manure.

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Oct 15 2019

Impossible Bug Burger

Published by under General Science

The market is innovating some burger alternatives in order to reduce demand for beef.  There are potentially three reasons to reduce beef consumption – health, environmental, and ethical. How successful are these replacements?

First let me quickly review the reasons for reducing beef. The health effects of eating red and processed meat are, at present, controversial. I reviewed this question recently at SBM. There is evidence for increased cancer and heart disease from eating large amounts of red and especially processed meat, but the absolute risk is low and the quality of the evidence is low. You can make of this what you will, and that’s the controversy. My take is that if you keep your total calories where they should be for weight maintenance, and eat plenty of fruits and vegetables, the rest takes care of itself.

The ethical concerns are complex and reflect personal values. Again, personally, I don’t have a problem with eating animals after they are dead, as long as they were treated humanely while they were alive and they were slaughtered in a humane way. However, I understand the points on the other side and respect the views of those who wish to avoid meat for ethical reasons. I currently file that away as a personal choice. I don’t think there is ethical justification for outlawing meat, however.

The environmental concerns are also complex, but it is clear that producing a lot of meat is very inefficient. Potatoes, for example, produce 17 times the amount of calories per acre than beef. But some land is better suited for grazing than farming. Cows also produce a lot of methane. Water usage from animals is also high. This does not mean the best thing to do is eliminate meat completely. Rather, as one study indicates, we should use land optimally. Some land is best for growing a certain kind of crop, while another might be best for grazing, while still other land is best left untouched for natural ecosystems.

Whether or not you think we should reduce meat consumption to zero or not, the evidence does suggest that industrialized nations are eating too much meat. So it is reasonable to moderate our meat consumption at the very least.

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Oct 10 2019

Ancient Food Storage

Published by under General Science

There are many things we take for granted in modern life, skills that humanity developed over literally hundreds of thousands of years, but also many modern conveniences that are fairly recent. One is food storage – saving food for later consumption.

We began as hunter-gatherers, a lifestyle that involves mostly consuming food right as it is acquired. This creates times of feast and famine, but little consistency or predictability. Without refrigeration and other techniques of food preservation, most foods would not last long. Cooked meat, gathered fruits might last a few days, while nuts and roots might last a bit longer. But that was about it.

Agriculture led to a significant increase in our control over our food supply. We could now store food as dried grains for months. As we cultivated crops, some were selected for storing well. Some hard-skinned squash, for example, can keep for several months. Cheese was a huge discovery, preserving milk calories also for months. Domesticated animals could be “preserved” indefinitely, and then slaughtered when needed. Salting, pickling, smoking, and curing were discovered over time as methods of preserving various foods. Industrialization eventually allowed for things like canning and, of course, refrigeration.

But what was the oldest and first example of humans preserving food for later consumption? Archaeologists think they have discovered it – researchers from Tel Aviv report the finding from Qesem Cave, a paleolithic human settlement from 400,000 years ago. They found evidence that the people living there would preserve deer and other bones for potentially up to 9 weeks, and then break them open to eat the marrow.

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