NEGATION OF THE NEGATION

Alan Turing and the Power of Negative Thinking

Mathematical proofs based on a technique called diagonalization can be relentlessly contrarian, but they help reveal the limits of algorithms.


ILLUSTRATION: KRISTINA ARMITAGE/QUANTA MAGAZINE
THE ORIGINAL VERSION of this story appeared in Quanta Magazine.

Algorithms have become ubiquitous. They optimize our commutes, process payments, and coordinate the flow of internet traffic. It seems that for every problem that can be articulated in precise mathematical terms, there’s an algorithm that can solve it, at least in principle.

But that’s not the case—some seemingly simple problems can never be solved algorithmically. The pioneering computer scientist Alan Turing proved the existence of such “uncomputable” problems nearly a century ago, in the same paper where he formulated the mathematical model of computation that launched modern computer science.

Turing proved this groundbreaking result using a counterintuitive strategy: He defined a problem that simply rejects every attempt to solve it.

“I ask you what you’re doing, and then I say, ‘No, I’m going to do something different,’” said Rahul Ilango, a graduate student at the Massachusetts Institute of Technology studying theoretical computer science.

Turing’s strategy was based on a mathematical technique called diagonalization that has a distinguished history. Here’s a simplified account of the logic behind his proof.
String Theory

Diagonalization stems from a clever trick for solving a mundane problem that involves strings of bits, each of which can be either 0 or 1. Given a list of such strings, all equally long, can you generate a new string that isn’t on the list?

The most straightforward strategy is to consider each possible string in turn. Suppose you have five strings, each five bits long. Start by scanning the list for 00000. If it’s not there, you can stop; if it is, you move on to 00001 and repeat the process. This is simple enough, but it’s slow for long lists of long strings.

Diagonalization is an alternate approach that builds up a missing string bit by bit. Start with the first bit of the first string on the list and invert it—that’ll be the first bit of your new string. Then invert the second bit of the second string and use that as the second bit of the new string, and repeat until you get to the end of the list. The bits you flip ensure that the new string differs from every string on the original list in at least one place. (They also form a diagonal line through the list of strings, giving the technique its name.)


ILLUSTRATION: MERRILL SHERMAN/QUANTA MAGAZINE

Diagonalization only needs to examine one bit from each string on the list, so it’s often much faster than other methods. But its true power lies in how well it plays with infinity.

“The strings can now be infinite; the list can be infinite—it still works,” said Ryan Williams, a theoretical computer scientist at MIT.

The first person to harness this power was Georg Cantor, the founder of the mathematical subfield of set theory. In 1873, Cantor used diagonalization to prove that some infinities are larger than others. Six decades later, Turing adapted Cantor’s version of diagonalization to the theory of computation, giving it a distinctly contrarian flavor.
The Limitation Game

Turing wanted to prove the existence of mathematical problems that no algorithm can solve—that is, problems with well-defined inputs and outputs but no foolproof procedure for getting from input to output. He made this vague task more manageable by focusing exclusively on decision problems, where the input can be any string of 0s and 1s and the output is either 0 or 1.

Determining whether a number is prime (divisible only by 1 and itself) is one example of a decision problem—given an input string representing a number, the correct output is 1 if the number is prime and 0 if it isn’t. Another example is checking computer programs for syntax errors (the equivalent of grammatical mistakes). There, input strings represent code for different programs—all programs can be represented this way, since that’s how they’re stored and executed on computers—and the goal is to output 1 if the code contains a syntax error and 0 if it doesn’t.

An algorithm solves a problem only if it produces the correct output for every possible input—if it fails even once, it’s not a general-purpose algorithm for that problem. Ordinarily, you’d first specify the problem you want to solve and then try to find an algorithm that solves it. Turing, in search of unsolvable problems, turned this logic on its head—he imagined an infinite list of all possible algorithms and used diagonalization to construct an obstinate problem that would thwart every algorithm on the list.

Imagine a rigged game of 20 questions, where rather than starting with a particular object in mind, the answerer invents an excuse to say no to each question. By the end of the game, they’ve described an object defined entirely by the qualities it lacks.

Turing’s diagonalization proof is a version of this game where the questions run through the infinite list of possible algorithms, repeatedly asking, “Can this algorithm solve the problem we’d like to prove uncomputable?”

“It’s sort of ‘infinity questions,’” Williams said.

To win the game, Turing needed to craft a problem where the answer is no for every algorithm. That meant identifying a particular input that makes the first algorithm output the wrong answer, another input that makes the second one fail, and so on. He found those special inputs using a trick similar to one Kurt Gödel had recently used to prove that self-referential assertions like “this statement is unprovable” spelled trouble for the foundations of mathematics.

The key insight was that every algorithm (or program) can be represented as a string of 0s and 1s. That means, as in the example of the error-checking program, that an algorithm can take the code of another algorithm as an input. In principle, an algorithm can even take its own code as an input.

With this insight, we can define an uncomputable problem like the one in Turing’s proof: “Given an input string representing the code of an algorithm, output 1 if that algorithm outputs 0 when its own code is the input; otherwise, output 0.” Every algorithm that tries to solve this problem will produce the wrong output on at least one input—namely, the input corresponding to its own code. That means this perverse problem can’t be solved by any algorithm whatsoever.
What Negation Can’t Do

Computer scientists weren’t yet through with diagonalization. In 1965, Juris Hartmanis and Richard Stearns adapted Turing’s argument to prove that not all computable problems are created equal—some are intrinsically harder than others. That result launched the field of computational complexity theory, which studies the difficulty of computational problems.

But complexity theory also revealed the limits of Turing’s contrary method. In 1975, Theodore Baker, John Gill, and Robert Solovay proved that many open questions in complexity theory can never be resolved by diagonalization alone. Chief among these is the famous P versus NP problem, which asks whether all problems with easily checkable solutions are also easy to solve with the right ingenious algorithm.

Diagonalization’s blind spots are a direct consequence of the high level of abstraction that makes it so powerful. Turing’s proof didn’t involve any uncomputable problem that might arise in practice—instead, it concocted such a problem on the fly. Other diagonalization proofs are similarly aloof from the real world, so they can’t resolve questions where real-world details matter.

“They handle computation at a distance,” Williams said. “I imagine a guy who is dealing with viruses and accesses them through some glove box.”

The failure of diagonalization was an early indication that solving the P versus NP problem would be a long journey. But despite its limitations, diagonalization remains one of the key tools in complexity theorists’ arsenal. In 2011, Williams used it together with a raft of other techniques to prove that a certain restricted model of computation couldn’t solve some extraordinarily hard problems—a result that had eluded researchers for 25 years. It was a far cry from resolving P versus NP, but it still represented major progress.

If you want to prove that something’s not possible, don’t underestimate the power of just saying no.

Original story reprinted with permission from Quanta Magazine, an editorially independent publication of the Simons Foundation whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and life sciences.

Understanding the Concept of the “Negation of the Negation”

By Steve McIntosh
April 15, 2022

In exploring Hegel’s concept of the “negation of the negation,” we came across this fascinating interpretation of his model in an out-of-print Marxist encyclopedia, which if nothing else, gets Hegel right. Its description of the dialectical process of development, and particularly how this process is best represented visually by a spiral, should be very familiar to us as Developmentalists:

One of the basic laws of the dialectic, which characterizes the direction of development, the unity of progress and continuity in development, the emergence of the new, and the relative recurrence of some elements of the old.

The law of the negation of the negation was first formulated by G. Hegel, but particular features of it had previously been established in philosophy (the dialectical character of negation, the role of continuity in development, and the nonlinear character of the direction of development). In Hegel’s dialectical system, development is the emergence of a logical contradiction and its subsequent sublation. In this sense, development is the birth of the internal negation of the previous stage, followed by the negation of this negation. To the extent that the negation of the previous negation proceeds by sublation, it is always, in a certain sense, the restoration of that which was negated, a return to a past stage of development. However, this is not a simple return to the starting point, but “a new concept, a higher, richer concept than the previous one, for it has been enriched by its negation or opposite; it contains in itself the old concept, but it contains more than this concept alone, and it is the unity of this and its opposite”. Thus, the law of the negation of the negation is the universal form of the splitting of a single whole and the transition of opposites into each other— that is, the universal manifestation of the law of the unity and struggle of opposites. Hegel exaggerated the significance of the triad as the operative form of the law of the negation of the negation and attempted to “subsume” under it all processes of change and development.

In materialist dialectics, the law of the negation of the negation is considered a law of the development of nature, society, and thought. If the law of the unity and struggle of opposites discloses the source of development, and the law of the transition of quantitative changes into qualitative changes reveals the mechanism of development, the law of the negation of the negation expresses the direction, form, and result of development. The effect of the law of the negation of the negation is fully revealed only in an integral, relatively complete process of development through a chain of interconnected transitions when it is possible to specify a more or less finished result of the process (from the point of view of the direction of development). At each particular stage, the law of the negation of the negation is usually revealed only as a tendency.

The concept of dialectical negation plays a primary role in disclosing the content of the law of the negation of the negation. If the old is not negated, the birth and maturation of the new and, consequently, the process of development, are impossible. According to the law of the negation of the negation, development takes place in cycles, each of which consists of three stages: the original state of the object, its transformation into its opposite (that is, its negation), and the transformation of the opposite into its own opposite.

Philosophers who think in metaphysical terms view negation as a discarding, as an absolute annihilation of the old. Development takes place when the new does not simply cut off the existence of the old but takes from it all that is positive and viable. This is “continuity in the discontinuous,” or successiveness within development. In the law of the negation of the negation, this is stated as the “repetition at a higher stage of certain features … of the lower stage and … the apparent return of the old”, but is actually the repetition of some of the essential elements of the old on a different, considerably more developed foundation. It also meant the transition to a new cycle with essentially different internal contradictions and laws of motion.

The succession of cycles that makes up the chain of development can be represented as a spiral. “A development that repeats, as it were, stages that have already been passed, but repeats them in a different way, on a higher basis (‘the negation of the negation’), a development, so to speak, that proceeds in a spiral, not in a straight line”. In such a representation, each cycle is one turn, one twist, in the spiral of development, and the spiral itself is a chain of cycles. Although the spiral is only an image representing the connection between two or more points in the process of development, it captures the general direction of development that takes place in accordance with the law of the negation of the negation. A return to that which has already been gone through is not a complete return: development does not repeat the paths already taken but seeks out new ones that conform to changed external and internal conditions. The more complex the process of development, the more relative is the repetition of certain features or properties encountered in previous stages.

The spiral characterizes not only the form but also the tempo of development. With each new turn, or twist, of the spiral, an even more significant path is left behind. Thus, it is possible to say that the process of development is linked with an acceleration of tempo and with continuous change in the internal time scale of a developing system. This regularity is found in the development of scientific knowledge, as well as in the development of society and of nature.

Space rocks and asteroid dust are pricey, but these aren’t the most expensive materials used in science

By Chris Impey
THE CONVERSATION

I use Moon and Mars rocks in my teaching and have a modest collection of meteorites. I marvel at the fact that I can hold in my hand something that is billions of years old from billions of miles away.

Meteorites can get pricey, but they’re not the most expensive material.

(Image credit: Photo/Thibault Camus)

After a journey of seven years and nearly 4 billion miles, NASA’s OSIRIS-REx spacecraft landed gently in the Utah desert on the morning of Sept. 24, 2023, with a precious payload. The spacecraft brought back a sample from the asteroid Bennu.


Roughly half a pound of material collected from the 85 million-ton asteroid (77.6 billion kg) will help scientists learn about the formation of the solar system, including whether asteroids like Bennu include the chemical ingredients for life.

NASA’s mission was budgeted at US$800 million and will end up costing around $1.16 billion for just under 9 ounces of sample (255 g). But is this the most expensive material known? Not even close.

I’m a professor of astronomy. I use Moon and Mars rocks in my teaching and have
a modest collection of meteorites. I marvel at the fact that I can hold in my hand something that is billions of years old from billions of miles away.

The cost of sample return

A handful of asteroid works out to $132 million per ounce, or $4.7 million per gram. That’s about 70,000 times the price of gold, which has been in the range of $1,800 to $2,000 per ounce ($60 to $70 per gram) for the past few years.

The first extraterrestrial material returned to Earth came from the Apollo program. Between 1969 and 1972, six Apollo missions brought back 842 pounds (382 kg) of lunar samples.

The total price tag for the Apollo program, adjusted for inflation, was $257 billion. These Moon rocks were a relative bargain at $19 million per ounce ($674 thousand per gram), and of course Apollo had additional value in demonstrating technologies for human spaceflight.

NASA is planning to bring samples back from Mars in the early 2030s to see if any contain traces of ancient life. The Mars Sample Return mission aims to return 30 sample tubes with a total weight of a pound (450 g). The Perseverance rover has already cached 10 of these samples.

However, costs have grown because the mission is complex, involving multiple robots and spacecraft. Bringing back the samples could run $11 billion, putting their cost at $690 million per ounce ($24 million per gram), five times the unit cost of the Bennu samples.

Some space rocks are free

Some space rocks cost nothing. Almost 50 tons of free samples from the solar system rain down on the Earth every day. Most burn up in the atmosphere, but if they reach the ground they’re called meteorites, and most of those come from asteroids.

Meteorites can get costly because it can be difficult to recognize and retrieve them. Rocks all look similar unless you’re a geology expert.

Most meteorites are stony, called chondrites, and they can be bought online for as little as $15 per ounce (50 cents per gram). Chondrites differ from normal rocks in containing round grains called chondrules that formed as molten droplets in space at the birth of the solar system 4.5 billion years ago.





A chondrite from the Viñales meteorite, which originated from the asteroid belt between Mars and Jupiter. (Image credit: Ser Amantio di Nicolao/Wikimedia Commons, CC BY-SA)

Iron meteorites are distinguished by a dark crust, caused by melting of the surface as they come through the atmosphere, and an internal pattern of long metallic crystals. They cost $50 per ounce ($1.77 per gram) or even higher. Pallasites are stony-iron meteorites laced with the mineral olivine. When cut and polished, they have a translucent yellow-green color and can cost over $1,000 per ounce ($35 per gram).

More than a few meteorites have reached us from the Moon and Mars. Close to 600 have been recognized as coming from the Moon, and the largest, weighing 4 pounds (1.8 kg), sold for a price that works out to be about $4,700 per ounce ($166 per gram).


An iron meteorite. (Image credit: Llez/Wikimedia Commons, CC BY-SA)

About 175 meteorites are identified as having come from Mars. Buying one would cost about $11,000 per ounce ($388 per gram).

Researchers can figure out where meteorites come from by using their landing trajectories to project their paths back to the asteroid belt or comparing their composition with different classes of asteroids. Experts can tell where Moon and Mars rocks come from by their geology and mineralogy.

The limitation of these “free” samples is that there is no way to know where on the Moon or Mars they came from, which limits their scientific usefulness. Also, they start to get contaminated as soon as they land on Earth, so it’s hard to tell if any microbes within them are extraterrestrial.

Expensive elements and minerals

Some elements and minerals are expensive because they’re scarce. Simple elements in the periodic table have low prices. Per ounce, carbon costs one-third of a cent, iron costs 1 cent, aluminum costs 56 cents, and even mercury is less than a dollar (per 100 grams, carbon costs $2.40, iron costs less than a cent and alumnium costs 19 cents). Silver is $14 per ounce (50 cents per gram), and gold, $1,900 per ounce ($67 per gram).

Seven radioactive elements are extremely rare in nature and so difficult to create in the lab that they eclipse the price of NASA’s Mars Sample Return. Polonium-209, the most expensive of these, costs $1.4 trillion per ounce ($49 billion per gram).

Gemstones can be expensive, too. High-quality emeralds are 10 times the price of gold, and white diamonds are 100 times the price of gold.


High-quality white diamonds can cost millions of dollars.

(Image credit: AP Photo/Mary Altaffer)

Some diamonds have a boron impurity that gives them a vivid blue hue. They’re found in only a handful of mines worldwide, and at $550 million per ounce ($19 million per gram) they rival the cost of the upcoming Mars samples – an ounce is 142 carats, but very few gems are that large.

The most expensive synthetic material is a tiny spherical “cage” of carbon with a nitrogen atom trapped inside. The atom inside the cage is extremely stable, so can be used for timekeeping. Endohedral fullerenes are made of carbon material that may be used to create extremely accurate atomic clocks. They can cost $4 billion per ounce ($141 million per gram).

Most expensive of all

Antimatter occurs in nature, but it’s exceptionally rare because any time an antiparticle is created it quickly annihilates with a particle and produces radiation.



The particle accelerator at CERN can produces 10 million antiprotons per minute. That sounds like a lot, but at that rate it would take billions of years and cost a billion billion (1018) dollars to generate an ounce (3.5 x 1016 dollars per gram).

Warp drives as envisaged by “Star Trek,” which are powered by matter-antimatter annihilation, will have to wait.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The views expressed are those of the author and do not necessarily reflect the views of the publisher.

GERMANY
Climate scientist and sustainable builder win top eco prize

Stuart Braun
DW

Climatologist Friederike Otto and low-carbon construction innovator Dagmar Fritz-Kramer have jointly won the German Environmental Award and its €500,000 prize for their efforts to limit global heating.

Extreme flooding in Germany in 2021 was made more likely by climate change: The German Environmental Award has been awarded to women looking for solutionsI

mage: Sebastien Bozon/Getty Images/AFP

Understanding how global heating, caused in large part by burning carbon-intensive fossil fuels, is worsening extreme weather such as floods, storms and droughts, and finding ways to create a carbon-neutral world define the work of this year's German Environmental Award winners.

Friederike Otto, climatologist at Imperial College London and co-founder of World Weather Attribution, which draws a connection between climate change and extreme weather events, and Dagmar Fritz-Kramer, the managing director of Baufritz, a climate-neutral building company utilizing low-carbon timber, shared the award presented on October 29.

"With the outstanding energy they have shown in their respective fields, both award winners have demonstrated that we cannot afford to lose any more time in the fight against the climate crisis," said Alexander Bonde, the secretary general of the German Federal Environmental Foundation (DBU – Deutsche Bundesstiftung Umwelt) behind the award.

"They are a true inspiration and motivation for us to learn from the impacts of global warming, which are already evident today, and to continue implementing more and more environmental and resource protection measures so that our planet remains a habitable place."

Recent review shows Germany unlikely to reach climate goals 01:37

Connecting climate change and extreme weather

When Friederike Otto was working on climate models as a postdoctoral student in Oxford in the early 2010s, she noticed that many in the scientific community were wary of attributing single extreme weather events to climate change.

There was a belief that it was too difficult to say whether global heating made a single storm or heat wave more likely, or more severe, she told DW.

"It was almost a dangerous thing for the scientific community not to say anything," she said of a failure to attribute the increasing frequency and impacts of extreme heat, flooding or storms to the changing climate.

But based on her own climate models — and her motivation to compare historical weather data when there was less warming compared to today — Otto "felt that we can do this." She then founded WWA with her colleague Geert Jan van Oldenborgh in 2015.

"I still think that in order for us to do something really about climate change, we need to connect our experiences with the theory," she said. "And that's what we do at World Weather Attribution, only that we do it quickly. When extreme events are happening, that's when people care about it, that's when people have questions."

Friederike Otto wanted to use her climate modeling experience to understand how rising temperatures make extreme weather more likely

TT/imago images

World Weather Attribution has since developed into a global network of experts that provide rapid analysis of the influence of human-caused climate change on world weather events: from the wildfires consuming southern Europe this summer to the extreme German floods of 2021, and to unprecedented heat waves in North America.

In recognition of the importance of this work, in 2021 both Otto and Oldenborgh were included in Time magazine's list of the top 100 most influential people.

"The reason why we are so successful is because there is a big demand in understanding the role of climate change in everyday experiences. We are more or less the only group doing this," she said.

Using scientific evidence to explain the link between worsening storms and heat waves and greenhouse gas emissions is also helping to hold those who create these emissions — including fossil fuel companies — accountable in the courts, Otto explained.

6 young people sue 32 nations over climate inaction  01:48

Beyond attribution analysis that is turned around quickly to accompany reporting of weather disasters, the climate scientist is embarking on deeper research to support claims for so-called loss and damage, or compensation, from climate vulnerable communities.

Otto told DW that despite the ever-increasing body of evidence linking extreme weather to global heating, she's also concerned about the increasing demonization of climate protesters and activists like Last Generation.

"The way they are talked about by politicians is really disconcerting," she said, adding that activist demands for rapid emission cuts are simply what "countries have signed up to anyway in the Paris agreement."

Climate activists protest by any means  01:33

Pioneering carbon-neutral housing in Germany

German Environmental Award co-winner Dagmar Fritz-Kramer is continuing a four-generation tradition of Baufritz builders using local timber from the Allgäu region of southern Germany and applying this heritage to constructing carbon-neutral housing.

Certified timber grown in sustainably managed European forests accounts for around 85% of the material used in a Baufritz house. The wood captures, on average, 50 metric tons of CO2 from the atmosphere per house after deducting the environmental impact from construction and transport. This saving is equivalent to the carbon emissions of an average mid-range car over 20 years.

"There was way too much resource consumption in the past," Fritz-Kramer told DW of a construction industry which, she said, produces 50% of all waste in Germany. Much of these materials are high-carbon concrete and steel, explaining why around 40% of Germany's annual planet-heating greenhouse gases are emitted by the sector.

Dagmar Fritz-Kramer has helped Baufritz to build homes mostly with low-carbon timber

Image: Jongebloed/DBU

This is why Fritz-Kramer is pushing for a "construction transition" in Germany, she said.

This will demand that new buildings are comprised largely of "renewable raw materials," but also that "we increasingly work with recycled building materials," she said, explaining other means to limit resource use. Renovation and upgrading of existing buildings to make them more sustainable, including by retrofitting renewable energy like solar, is also key, she said.

With around 65% of the 21 million buildings in Germany still heated with climate-wrecking oil and gas, according to Fritz-Kramer, she is determined to help make all buildings climate-neutral by 2045 to fulfill Germany's net-zero targets.

"She and her company are a true driving force of industry and the changes shaping the construction sector," said DBU's Bonde of Baufritz's efforts to make sustainable construction mainstream.

Switzerland: Building a cement-free future  03:24

Award winners collaborate on climate mitigation

Dagmar Fritz-Kramer and Friederike Otto are, in fact, working together to generate climate finance for sustainable, low-carbon buildings.

Working with some of Otto's students at Imperial College London, Fritz-Kramer said the project aims to show how responding to the climate crisis with carbon-neutral construction can also become an opportunity to grow the economy.

Arctic shifts are driving dramatic population swings among gray whales, study explains

A gray whale breaching. 

(Credit: NOAA Fisheries (Photo taken under permit))

OCTOBER 29, 2023

by StudyFinds

CORVALLIS, Ore. — Gray whales undergo substantial “boom-and-bust” population cycles in response to shifting Arctic conditions, new research reveals. Since the 1980s, scientists have observed three significant die-offs in the eastern North Pacific gray whale population. Each die-off, including an ongoing one that started in 2019, has led to a reduction in the gray whale population by as much as 25 percent within just a few years.

“These are extreme population swings that we did not expect to see in a large, long-lived species like gray whales. When the availability of their prey in the Arctic is low, and the whales cannot reach their feeding areas because of sea ice, the gray whale population experiences rapid and major shocks,” says the study’s lead author Dr. Joshua Stewart, assistant professor with Oregon State University’s Marine Mammal Institute, in a media release. “Even highly mobile, long-lived species such as gray whales are sensitive to climate change impacts.”

The researchers note that the eastern North Pacific gray whales, having rebounded from the effects of commercial whaling, are likely nearing the carrying capacity of their Arctic feeding areas, making them more vulnerable to environmental changes due to resource competition.

Gray whales migrating south between their summer feeding grounds in the Arctic and wintering lagoons in Mexico. Permit number 14097. 

(Credit: NOAA Fisheries/SWFSC/MMTD)

Interestingly, the harsh Arctic conditions causing two of the die-offs in the 1980s and 1990s weren’t permanent. The whale population swiftly bounced back when conditions became favorable.

“It turns out we didn’t really know what a healthy baleen whale population looks like when it isn’t heavily depleted by human impacts. Our assumption has generally been that these recovering populations would hit their environmental carrying capacities and remain more or less steady there,” says Dr. Stewart. “But what we’re seeing is much more of a bumpy ride in response to highly variable and rapidly changing ocean conditions.”

Currently, about 14,500 eastern North Pacific gray whales make an impressive 12,000-mile annual migration along the Pacific Coast, transitioning from the warm waters off Baja California, Mexico, during winter to the chilly, nutrient-rich waters of the Arctic for summer feeding. For decades, the National Oceanic and Atmospheric Administration Southwest Fisheries Science Center in California has monitored this species, making the eastern North Pacific gray whales among the most extensively researched large whale populations globally.

“When we began collecting data on gray whales in 1967, little did we realize the important role they would play in understanding the effects of climate change on an iconic sentinel species in the Pacific. This research would not have been possible without our reliable long-term record,” says Dr. Dave Weller from the Southwest Fisheries Science Center.

A Southwest Fisheries Science Center researcher scans for gray whales during a survey as part of the long-term population monitoring research.

 (Credit: NOAA Fisheries)

The research team’s analysis, which linked long-term data on gray whales with Arctic environmental information, found connections between the “Unusual Mortality Events” in 1999 and 2019 and factors like sea ice levels and the crustacean food source for the whales. They also identified a similar event in the 1980s that wasn’t associated with a surge in strandings, likely due to less efficient reporting before the 1990s.

Though shorter ice-covered periods in the Arctic initially seem beneficial for the whales, this trend, accelerated by climate change, may not be sustainable. The whales’ primary food source, benthic amphipods, relies on the sea ice. Algae growing beneath the ice nourish the amphipods, but less ice means less sustenance for them. As a result, smaller crustaceans thrive in warmer waters, and faster currents diminish habitats for the preferred whale prey.

“With less ice, you get less algae, which is worse for the gray whale prey. All of these factors are converging to reduce the quality and availability of the food they rely on,” Dr. Stewart emphasizes.

The current die-off event, according to Dr. Stewart, is lingering much longer than its predecessors. He postulates that the sustained impact might be due to the long-term shift in prey quality induced by climate change.

“An Arctic Ocean that has warmed significantly may not be able to support 25,000 gray whales like it has in the recent past,” Dr. Stewart cautions.

However, given the gray whale’s ability to adapt over hundreds of thousands of years, the team remains optimistic about the animal’s long-term survival.

The study is published in the journal Science.

South West News Service writer Stephen Beech contributed to this report.

Tracking down environmental toxins

Detection of per- and polyfluoroalkyl substances (PFAS) by interrupted energy transfer

Date:October 27, 2023

Source:Wiley

PFAS, a family of highly fluorinated substances, represent a danger for humans and the environment. Particularly problematic members of this family, such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) appear to cause organ damage and cancer, as well as disrupting the endocrine system. In the journal Angewandte Chemie, researchers have now introduced a new method for an economical, easy-to-use fluorescence sensor for sensitive on-site testing for PFAS in water samples.

The term per- and polyfluoroalkyl substances (PFAS) refers to a group of organic compounds in which most or all the hydrogen atoms bound to the carbon atoms have been replaced with fluorine atoms. They are used to provide water-, oil-, and dirt-resistance to a variety of products, such as nonstick pans, outdoor clothing, and packaging. They may also be found in fire-suppressing foam, paint, and car polish. These compounds are highly useful -- and highly dangerous when they find their way into the environment: they do not break down and thus become concentrated in plants, animals, and people.

Limits of 100 ng/l for individual specific PFAS substances and 500 ng/l for the total of all PFAS were set for drinking water in the EU. In Germany, water providers must begin testing drinking water for PFAS in 2026. The US Environmental Protection Agency has set stricter limits: for the most widespread PFAS (PFOS and PFOA), the upper limit is set at 4nm/l for each substance.

The usual method used to detect such trace amounts involves chromatography and mass spectrometry, is time-consuming and expensive, and requires complex equipment and experienced personnel. Timothy M. Swager and Alberto Concellón at the Massachusetts Institute of Technology (MIT) in Cambridge, USA, have now introduced a technique for making a portable, inexpensive test that uses fluorescence measurements to easily and selectively detect PFAS in water samples.

The test is based on a polymer -- in the form of a thin film or nanoparticles -- with fluorinated sidechains that have fluorinated dye molecules (squaraine derivatives) embedded in them. The special polymer backbone (poly-phenylene ethynylene) absorbs violet light and transfers the light energy to the dye by an electron exchange (Dexter mechanism). The dye then fluoresces red. If PFAS are present in the sample, they enter the polymer and displace the dye molecules by a fraction of a nanometer. This is enough to stop the electron exchange and thus the energy transfer. The dye's red fluorescence is "switched off," while the blue fluorescence of the polymer is "switched on." The degree of fluorescence change is proportional to the concentration of PFAS.

This new technique, which has a detection limit in the µg/l range for PFOA and PFOS is suitable for on-site detection in highly contaminated regions. Detection of trace amounts of these contaminants in drinking water can be achieved with sufficient precision after pre-concentration of the samples by solid-phase extraction.

Journal Reference:

Alberto Concellón, Timothy M. Swager. Detection of Per‐ and Polyfluoroalkyl Substances (PFAS) by Interrupted Energy Transfer. Angewandte Chemie International Edition, 2023; DOI: 10.1002/anie.202309928

SCI-FI-TEK

ABB and Imperial agree second decade of carbon capture collaboration

29 Oct 2023

Technology giant ABB and Imperial College London have renewed their longstanding carbon capture joint venture for a second 10 year period.

To date, since 2012, the site has trained an estimated 4,500 students in the use of ABB’s state-of-the-art technology solutions. The plant, said to be the only one of its kind in the world, employs more than 250 instrument and sensors feeding data and measurements to a distributed control system intended to replicate actual working conditions. 

Senior Teaching Fellow at Imperial Dr Colin Hale, explained that the original purpose of the venture had been to tackle the shortage of recruits for chemical engineering.

“One of the ways to do this was to set up this carbon capture plant so we could enthuse students to follow through on the environmental topics they have learnt previously. ABB shares this collective vision,” said Hale.

Head of Energy Industries, ABB UK & Ireland Simon Wynne added that extending the partnership with Imperial provided students with necessary practical training to prepare for a career in industry. He pointed out a recent EngineeringUK report had assessed that more scientists were needed with sufficient skills to ensure the UK met emissions targets by 2050.

Interest in the potential demand for carbon capture and storage (CCS) appears to be borne out by the Global CCS Institute which, says ABB, cited that in 2022 there was a 44 percent increase in the number of CCS facilities around the world compared with the previous year.

With this in mind, ABB is investing heavily in technology solutions to lower the capital and operational investment cost,  enable integration of carbon capture technology into existing and new operations and ensure the scale-up of commercial CCS.

In March 2023 ABB signed an agreement with London-based Pace CCS to improve access to the capture, transportation and storage of industrial carbon dioxide emissions more accessible, employing digital twin technology to to provide proof of concept. Again this year, the Government’s Powering Up Britain policy for net-zero this year pledged £20 billion to encourage private investment and jobs in CCS.

Bacteriophages Enhance Cellular Growth and Survival for Mammalian Cells

October 29, 2023

Bacteriophage particle interacting with mammalian cells.[T2Q and Barr Lab

 (CC-BY 4.0, https://creativecommons.org/licenses/by/4.0/)]

Phage interactions with bacteria are well known, and interactions between bacteria and their mammalian host can lead to a range of symbioses. However, the impact of bacteriophages on mammalian cellular and immunological processes is not well understood. Now, a new study by researchers at Monash University suggests that mammalian cells internalize phages as a resource to promote cellular growth and survival.

The findings are published in PLOS Biology in an article titled, “Mammalian cells internalize bacteriophages and use them as a resource to enhance cellular growth and survival.”

“There is a growing appreciation that the direct interaction between bacteriophages and the mammalian host can facilitate diverse and unexplored symbioses,” wrote the researchers. “Yet the impact these bacteriophages may have on mammalian cellular and immunological processes is poorly understood. Here, we applied highly purified phage T4, free from bacterial byproducts and endotoxins to mammalian cells and analyzed the cellular responses using luciferase reporter and antibody microarray assays.”

In order to investigate how mammalian cells’ immune responses interact with and are modulated by interactions with phages, researchers led by Jeremy J. Barr, PhD, associate professor at Monash University, applied phage T4 to mammalian cells in vitro and analyzed the cellular responses using luciferase reporter and antibody microarray assays.

The researchers found that T4 phages did not activate DNA-mediated inflammatory pathways, but triggered a sequence of signaling pathway events that promote cellular growth and survival.

“Highly purified T4 phages were rapidly internalized by mammalian cells and accumulated within macropinosomes but did not activate the inflammatory DNA response TLR9 or cGAS-STING pathways,” noted the researchers. “Following 8 hours of incubation with T4 phage, whole cell lysates were analyzed via antibody microarray that detected expression and phosphorylation levels of human signaling proteins. T4 phage application led to the activation of AKT-dependent pathways, resulting in an increase in cell metabolism, survival, and actin reorganization, the last being critical for macropinocytosis and potentially regulating a positive feedback loop to drive further phage internalization.”

Future studies are needed to determine why cells use phage particles as resources, and whether they have specifically evolved via adaptation to benefit from this internalization.

According to the authors, “This preliminary study provides novel insights into the impact phages have on mammalian systems, with broader potential implications across the fields of immunology, phage therapy, microbiome, and human health.”

Barr added, “This work provides new insights into the additional benefits that bacteriophages may have on their mammalian hosts. This is of particular importance given the increased use of phage therapy to treat antibiotic-resistant infections.”

SEE

https://plawiuk.blogspot.com/search?q=PHAGES

 https://plawiuk.blogspot.com/search?q=BIOPHAGES

 https://plawiuk.blogspot.com/search?q=PHAGE

 https://plawiuk.blogspot.com/search?q=BACTERIOPHAGE

Robots at your doorstep: acceptance of near-future technologies for automated parcel delivery

Maher Said,
Spencer Aeschliman &
Amanda Stathopoulos

Scientific Reports volume 13, Article number: 18556 (2023) Cite this article

Article
Open access
Published: 29 October 2023
details


Abstract

The logistics and delivery industry is undergoing a technology-driven transformation, with robotics, drones, and autonomous vehicles expected to play a key role in meeting the growing challenges of last-mile delivery. To understand the public acceptability of automated parcel delivery options, this U.S. study explores customer preferences for four innovations: autonomous vehicles, aerial drones, sidewalk robots, and bipedal robots. We use an Integrated Nested Choice and Correlated Latent Variable (INCLV) model to reveal substitution effects among automated delivery modes in a sample of U.S. respondents. The study finds that acceptance of automated delivery modes is strongly tied to shipment price and time, underscoring the importance of careful planning and incentives to maximize the trialability of innovative logistics options. Older individuals and those with concerns about package handling exhibit a lower preference for automated modes, while individuals with higher education and technology affinity exhibit greater acceptance. These findings provide valuable insights for logistics companies and retailers looking to introduce automation technologies in their last-mile delivery operations, emphasizing the need to tailor marketing and communication strategies to meet customer preferences. Additionally, providing information about appropriate package handling by automated technologies may alleviate concerns and increase the acceptance of these modes among all customer groups.

Introduction

The last-mile logistics of freight distribution is a critical and challenging aspect of the supply chain. It is often the least efficient and most expensive stage1,2,3, accounting for up to 28% of delivery transportation costs, and is a considerable source of congestion and other externalities, such as pollution and noise2,3,4,5. These inefficiencies and negative impacts on citizen well-being make improving last-mile logistics a priority for businesses and policymakers alike2. Last-mile delivery challenges are likely to become more pressing due to factors such as increased e-commerce, rising consumer expectations, and the growth of ride-hailing competing for scarce curbspace6. Increased e-commerce and expectations for speed by consumers have been tied to the growing volume of parcels, smaller shipment sizes, and higher frequency of delivery trips7. Additionally, the rapid proliferation of ridehailing services presents a series of novel challenges to the effective management of curbside operations, including reduced available space for loading and parking for conventional urban delivery vehicles8,9,10. The global COVID-19 pandemic, the transformation of work, and a corresponding surge in e-commerce and delivery demands11,12 have also brought to light critical vulnerabilities in the supply chain, particularly related to cascading disruptions, lasting reliance on residential home-deliveries, and labor shortages13,14.

To address these challenges, firms such as Amazon, Walmart, Einride, Eliport, and UPS are exploring the deployment of autonomous freight delivery options15,16. The market size for automated delivery technologies, including autonomous vehicles (AVs), drones, and robots, is projected to reach $665 billion (about $2,000 per person in the US) by 2030, representing up to 20% of the package delivery industry17. These technologies offer numerous benefits, including greater efficiency, safety, and sustainability, and can help reduce human error. Smaller-scale automation technologies, such as drones and delivery robots, can offer more efficient, safer, cheaper, and sustainable solutions than traditional truck deliveries by, for example, bypassing congested streets and curbsides15,16. Yet, the shift towards automation can be fraught with negative effects on employment, safety, and security, and open questions about shipping performance, operational needs, and regulatory support18. However, by combining various automated delivery technologies, such as launching drones from autonomous vehicles, it is possible to mitigate these drawbacks and enhance efficiency compared to single technology operations15,16. Combined systems can address obstacles for ground delivery in urban environments and expand service in suburban and rural areas, where higher delivery costs are a significant challenge19,20,21. Thus, the (combined) deployment of robots, autonomous vehicles, and drones holds promise for addressing reliance on human drivers, managing curbside challenges, meeting growing demand and customer expectations, and preparing for future disruptions22,23,24.

The materialization of these benefits, however, is dependent on the adoption and public acceptability of these technologies25. While most acceptability research to date has focused on self-driving vehicle use among passengers19,20,21,26,27, limited insight exists on customer attitudes toward near-future automated delivery modes25,28,29,30,31,32,33. Both delivery performance attributes and attitudes toward automated services will play a role in their acceptance. Existing studies find that acceptance is linked to the perceived usefulness, convenience, and flexibility of automated parcel delivery28,31,32,33,34,35,36, all constructs related to cost and delivery speed. Studies also identify several adoption barriers, namely concerns over package handling, security, and privacy, as well as a lack of trust and familiarity25,28,29,30,31,32,33. The role of environmental concerns is not yet clear. Research is still needed to determine the impact of automation on supply chain sustainability. For example, recent simulation work suggests that while drones offer some energy efficiency improvements over traditional delivery, their per-day energy consumption would be comparable to battery electric vehicles on normal days and as high as diesel trucks on windy days37. Other work suggests that drone delivery leads to lowered CO2 emissions for logistics38. Additionally, the link between customers' perceptions of the environmental impact of delivery automation and their acceptance of these technologies remains ambiguous39. A general takeaway is that the acceptability of automated delivery options depends on a complex set of attitudinal, demographic, and market-based factors. A current challenge is that studies generally focus on a single technology (e.g. Figliozzi and Jennings40 and Hwang et al.41), while in reality customers will likely be faced with a portfolio of innovative options, and make trade-offs between several delivery attributes at once. A notable exception is Polydoropoulou et al.42, who study a multi-option decision context in a choice experiment in Greece, finding that respondents were generally unwilling to opt for innovative delivery modes over traditional ones due to cost, lack of familiarity, and infrastructure barriers. More research is needed to understand the relative importance of these different factors and how they interact, especially in light of multiple competing or complementary automation technologies, and different urban delivery contexts.

This paper aims to understand the potential acceptability of near-future automated delivery technologies among U.S. customers. The paper makes three main contributions to the literature. First, we study the adoption likelihood of a portfolio of multiple innovative delivery automation technologies in tandem. We design a Bayesian efficient choice experiment including traditional delivery along with four automated delivery innovations: (a) autonomous vehicles, (b) drones, (c) sidewalk robots, and (d) bipedal robots. This multi-technology setting enables us to examine patterns in customer acceptability and relationships among similar technologies. Second, we examine the role of shipping attributes, shipped item type, and socio-demographic and behavioral variables, thereby revealing the role of personal and shipping characteristics on the preference over future technologies. Third, we explore the impact of attitudes on delivery mode preferences. Specifically, we study the role of packaging preferences, environmental awareness, and affinity towards technology on the acceptability of automated delivery technologies.

Using an Integrated Nested Choice and Correlated Latent Variable (INCLV) model, we account simultaneously for dependence across alternative technologies and for correlated attitudinal latent variables, uncovering critical factors that influence customer acceptance of automated parcel delivery innovation. The model reveals the importance of attributes like shipment price, time performance, customer-specific attributes like age and education, and attitudes such as concerns about package handling and affinity towards technology. Scenario simulation is applied to examine business strategies and contextual events on the preference for automation. Our findings provide valuable insight and recommendations for analysts, policymakers, and practitioners, including retailers and couriers, seeking to successfully introduce these technologies to the market while mitigating their negative impacts on customers, society, and the environment.

Survey shows 60% of Japanese wrongly believe antibiotics can treat a cold

COLDS ARE BACTERIA NOT VIRUSES

In an online survey, nearly 67% of parents with preschool children said they believe antibiotics can fight viruses, while roughly 56% said they can cure a cold. |

 BLOOMBERG

KYODO

Oct 29, 2023

Nearly 60% of people erroneously believe that antibiotics are effective in treating a cold, according to a recent survey in Japan, with medical experts warning their misuse and overuse can increase antimicrobial resistance.

Both the common cold and influenza are viral infections, meaning antibiotics are ineffective treatments. The same is true of a sore throat or a runny nose, according to the Center Hospital of the National Center for Global Health and Medicine in Tokyo.

In an online survey of 500 people, nearly 67% of parents with preschool children said they believe antibiotics can fight viruses, while roughly 56% said they can cure a cold.

In a separate survey, about 63% of people aged 15 and older said that they believe the drugs can cure viral infections.

Influenza, colds and COVID-19 are the top three viruses many respondents thought antibiotics can treat, the hospital said.

Misuse and overuse of antimicrobials are the main factors in the development of drug-resistant pathogens, making infections harder or impossible to combat, according to the World Health Organization.

The Japanese government has said it is concerned about antimicrobial resistance, which is widely considered a "silent pandemic" among medical professionals.

The government has drawn up a five-year action plan in a bid to get a handle on the problem, setting itself the target of reducing daily use of antibiotics per 1,000 people by 15% by the final year from 2020 levels.

BIOLOGY 10

Where the heck did all those structures inside complex cells come from?

There are competing theories about the origin of the nucleus and endoplasmic reticulum.

VIVIANE CALLIER, KNOWABLE MAGAZINE - 10/29/2023

Enlarge / Computer illustration of mitochondria, membrane-enclosed cellular organelles that produce energy.

KATERYNA KON/SCIENCE PHOTO LIBRARY/GETTY15WITH

More than 1.5 billion years ago, a momentous thing happened: Two small, primitive cells became one. Perhaps more than any event—barring the origin of life itself—this merger radically changed the course of evolution on our planet.

One cell ended up inside the other and evolved into a structure that schoolkids learn to refer to as the “powerhouse of the cell”: the mitochondrion. This new structure provided a tremendous energetic advantage to its host—a precondition for the later evolution of complex, multicellular life.

But that’s only part of the story. The mitochondrion is not the only important structure within complex, eukaryotic cells. There’s the membrane-bound nucleus, safekeeper of the genome. There’s a whole system of internal membranes: the endoplasmic reticulum, the Golgi apparatus, lysosomes, peroxisomes and vacuoles—essential for making, transporting, and recycling proteins and other cargo in and around the cell.

Where did all these structures come from? With events lost in the deep past and few traces to serve as evolutionary clues, it’s a very tough question to tackle. Researchers have proposed various hypotheses, but it is only recently, with some new tools and techniques, that cell biologists have been able to investigate the beginnings of this intricate architecture and shed some light on its possible origins.

A microbial merger

The idea that eukaryotes originated from two cells merging dates back more than 100 years but did not become accepted or well-known until the 1960s, when the late evolutionary biologist Lynn Margulis articulated her theory of endosymbiosis. The mitochondrion, Margulis said, likely originated from a class of microbes known as alphaproteobacteria, a diverse group that today includes the bacterium responsible for typhus and another one important for the genetic engineering of plants, among many others.

Nothing was known about the nature of the original host cell. Scientists proposed that it already was fairly complicated, with a variety of membrane structures inside it. Such a cell would have been capable of engulfing and ingesting things—a complicated and energetically expensive eukaryotic feature called phagocytosis. That might be how the mitochondrion first got into the host.

But this idea, called the “mitochondria late” hypothesis, doesn’t explain how or why the host cell had become complex to begin with.

In 2016, evolutionary biologist Bill Martin, cell biologist Sven Gould and bioinformatician Sriram Garg, at the University of Dusseldorf in Germany, proposed a very different model known as the “mitochondria early” hypothesis. They argued that since no primitive cells today have any internal membrane structures, it seems very unlikely that a cell would have had these over 1.5 billion years ago.

Instead, the scientists reasoned, the endomembrane system—the whole hodgepodge of parts found inside complex cells today — could have evolved soon after the alphaproteobacterium took up residence inside a relatively simple host cell, of a kind from a class called archaea. The membrane structures would have arisen from bubbles, or vesicles, released by the mitochondrial ancestor.

Free-living bacteria shed vesicles all the time, for all sorts of reasons, Gould, Garg, and Martin note, so it seems reasonable to think they’d continue to do that when enclosed inside a host.

Eventually, these vesicles would have become specialized for the functions that membrane structures perform today inside eukaryotic cells. They would even fuse with the host cell’s membrane, helping to explain why the eukaryote plasma membrane contains lipids with bacterial features

Vesicles could have served an important initial function, says biochemist Dave Speijer of the University of Amsterdam. The new endosymbiont would have generated plenty of poisonous chemicals called reactive oxygen species, by oxidizing fatty acids and burning them for energy. “These destroy everything, they are toxic, especially on the inside of a cell,” Speijer says. Sequestering them inside vesicles would have helped keep the cell safe from harm, he says.

Another problem created by the new guest could also have been helped by making membrane barriers, Gould, Garg, and Martin add. After the alphaproteobacterium arrived, bits of its DNA would have mixed with the genome of the archaeal host, interrupting important genes. Fixing this would mean evolving machinery to splice out these foreign pieces—today they’re known as introns—from the messenger RNA copies of genes, so those protein-making instructions wouldn’t be garbled.

But that created yet another problem. The protein-making machinery—the ribosome—works extremely fast, joining several amino acids together per second. In contrast, the intron-removing system of the cell is slow, snipping out about one intron per minute. So unless the cell could keep the mRNA away from ribosomes until the mRNA was properly processed, the cell would produce many nonsensical, useless proteins.

The membrane surrounding the nucleus provided an answer. Serving as a spatial barrier, it allows mRNA splicing to finish up in the nucleus before the intron-free mRNA is translated in the cell’s internal fluid, the cytosol. “This is the selective pressure behind the origin of the nucleus,” Martin says. To form it, vesicles secreted by the endosymbiont would have flattened and wrapped around the genome, creating a barrier to keep ribosomes out but still allowing small molecules to pass freely.

An inside-out explanation

In short, Gould, Garg, and Martin’s hypothesis explains why endomembrane compartments evolved: to solve problems created by the new guest. But it doesn’t fully explain how the alphaproteobacterium got inside the host to begin with, says cell biologist Gautam Dey at EMBL in Heidelberg, Germany; it assumes the endosymbiont is already inside. “This is a massive problem,” Dey says.

An alternative idea, proposed in 2014 by cell biologist Buzz Baum of University College London (with whom Dey once worked) and his cousin, University of Wisconsin evolutionary biologist David Baum, is the “ inside-out” model. In this scenario, the alphaproteobacterium and the archaeal cell destined to be its eventual host would have lived side by side for millions of years in an intimate symbiosis, each depending on the other’s metabolic products.

The archaeal cell would have had long protrusions, as seen on some modern-day archaea that live in close association with other microbes. The alphaproteobacterium would have nestled up against these slender extensions.

Eventually, the protrusions would have wrapped around the alphaproteobacterium and enclosed it completely. But during the long stretch of time before that happened, the archaeal cell would have begun some spatial division of labor: It would keep information-processing jobs in its center, where the genome was, while functions like protein building would take place in the cytosol within the protrusions.

The power of the inside-out model, Buzz Baum says, is that it gives the cell eons of time, before the alphaproteobacterium becomes fully enclosed, to evolve ways to regulate the number and size of the mitochondrion and other membrane compartments that would eventually become fully internal. “Until you can regulate them, you’re dead,” Buzz Baum says.

The model also explains why the nucleus has the shape that it does; in particular, it provides an explanation for its unusually large pores. Viewed from inside the center of an archaeal cell, the long protrusions would be openings that could naturally become big pores like those, Baum says.

Most important, the inside-out model explains how the alphaproteobacterium would have gotten inside the archaeal host in the first place.

Still, the inside-out model has features it needs to explain. For example, the mitochondrion would end up in the wrong place—inside the endoplasmic reticulum, the network of tubes on which sit the cell’s protein-making ribosomes, as the archaeal protrusions wrapped around it. And so an additional step would be required to get the alphaproteobacterium into the cytoplasm.

But Martin’s main objection is that the inside-out model does not provide an evolutionary pressure that would have caused the nucleus or other membrane-bound compartments to arise in the first place. The inside-out model “is upside-down and backwards,” Martin says.

The nucleus: A riddle in the middle

Though the models agree that the mitochondrion evolved from an alphaproteobacterium, they have very different ideas about the origin of the nucleus and other organelles.

In the Gould, Garg, and Martin model, the source for all of the structures would have been vesicles released by the evolving mitochondrion. Vesicles to contain reactive chemicals or cellular cargo, and the ability to move this cargo around, would have evolved very early. The nucleus would have come later.

In the inside-out model, the nucleus was, essentially, the remains of the archaeal cell after it wrapped its membranes around the alphaproteobacterium. So it would have appeared immediately. The endoplasmic reticulum also would have formed early, created from those squished-together protrusions. Other organelles would have come later—arising, Buzz Baum says, from buds of archaeal membrane.

Thus the models also make different predictions about the chemical nature of the membranes of cell organelles—at least originally—and how today’s complex cells came to have membrane lipids that are all chemically like the ones in bacteria, not archaea.

In the Gould, Garg, and Martin model, in the beginning all the membranes except for the host cell’s outermost one would have been bacterial, like the membranes of the new resident. Then, as bacterial vesicles fused with this archaeal outer membrane, the bacterial lipids would slowly replace the archaeal ones.

In the inside-out model, the membranes of the nucleus and endoplasmic reticulum—and probably others—would have been archaeal, like the host, to start. Only later on, after genes from the bacterial genome moved over to the archaeal genome, would the lipids become bacterial in nature, Baum suggests.

How to test these ideas? Through experiments, cell biologists are starting to glimpse ways in which simple vesicles could have diversified into different organelles with distinct jobs—by taking on different shapes, like the layered membrane stacks of the modern endoplasmic reticulum or the Golgi body, or by ending up with different proteins inside them or on their membranes.

They are also highlighting the dynamism of the modern-day mitochondrion—and its potential to spawn new membrane structures.

Take, for example, the compartment that Speijer thinks evolved early in order to deal with reactive oxygen species: the peroxisome.

In 2017, cell biologist Heidi McBride of McGill University in Montreal reported that cells lacking peroxisomes could generate them from scratch. Working with mutant human fibroblast cells without peroxisomes, her team found that these cells put proteins that are essential for peroxisome function into mitochondria instead. Then the mitochondrial membrane released them as little bubbles, or vesicles.

These vesicles, or proto-peroxisomes, matured into true peroxisomes when they fused with another type of vesicle derived from endoplasmic reticulum, which carry a third necessary peroxisome protein. “It’s a hybrid organelle,” McBride says.

For McBride, this is an indication that peroxisomes—and probably other organelles—originally came from mitochondria (not exclusively from the endoplasmic reticulum, as previously believed). “The presence of mitochondria launched the biogenesis of new organelles,” she says. “In the case of peroxisomes, it’s quite direct.”

Other mitochondrion antics have also been noted.

First, a 2021 report from the lab of biochemist Adam Hughes at the University of Utah found that when yeast cells are fed toxic amounts of amino acids, their mitochondria will shed vesicles that are loaded with transporter molecules. The transporters move amino acids into the vesicles, where they won’t poison the mitochondria.

Hughes also discovered that the vesicles shed by the mitochondria can form long, tubule-like extensions with multiple layers, reminiscent of the layered stacks of the endoplasmic reticulum and the Golgi body. The structures persist in the cell for a long time. “They’re definitely their own unique structure,” Hughes says.

And in 2022, immunologist Lena Pernas, now at UCLA, showed that multilayered, mitochondria-derived structures can form in other contexts, too. When a cell is infected by the parasite Toxoplasma, her team found, the mitochondria surround the parasite and change shape. The parasite responds, and the upshot is that the mitochondrion ends up shedding large bits of outer membrane.

Pernas, who wrote about mitochondrial remodeling in the Annual Review of Physiology in 2016, recently discovered that these structures, which initially look like simple vesicles, also can grow and take on more complex shapes, such as stacks of sheet-like layers. What’s more, the stress of infection changes what sorts of proteins are placed on these shed bits of mitochondrial membrane. Such changes open the door for the stacked sheets to behave in different ways than they normally would, presenting the opportunity to take on new jobs, Pernas says.

The more Pernas and Hughes study these structures—found in quite different cells and conditions—the more similar they look. It’s tantalizing, says Hughes, to imagine how a structure like this, forming in the early days of eukaryote evolution, could have evolved over eons of natural selection into some of the endomembrane compartments existing in cells today.

It may never be possible to know for sure what happened such a very long time ago. But by exploring what can happen in today’s living bacterial, archaeal, and eukaryotic cells, scientists can get more clarity on what was possible—and even probable. A cell moves into another cell, bringing benefits but also problems, setting off a complex cascade. And then, McBride says, “all this stuff blooms and blossoms.”

Viviane Callier is a freelance science journalist in Rockville, Maryland. This article originally appeared in Knowable Magazine, an independent journalistic endeavor from Annual Reviews.