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Earth’s first lifeforms breathed arsenic, not oxygen
The microbes that eventually produced the planet's oxygen had to breathe something, after all.
- We owe the Earth's oxygen to ancient microbes that photosynthesized and released it into the world's oceans.
- A long-standing question has been: Before oxygen, what did they breathe?
- The discovery of microbes living in a hostile early-Earth-like environment may provide the answer.
One of the most interesting natural organizations studied by scientists are microbial mats, communities of cyanobacteria (AKA, "blue-green algae"). These fascinating self-contained ecosystems are visible to the naked eye and can be found all over the place: in lakes and streams, in soil, and even in man-made environs such as gutters and drinking fountains. Given enough time — say two to three thousand years — microbial mats fossilize layer-by-layer into carbonized stromatolites, our oldest fossils. They've been doing this for about 3.7 billion years.
Scientists believe these ancient microbial photosynthesizers are responsible for the oxygen we breathe. Prior to their arrival, the planet's atmosphere was only about 1 percent oxygen. What could they have been breathing for the first 1.5 billion years, and how did they execute photosynthesis without oxygen?
In a new study published in Communications Earth & Environment, researchers led by Pieter T. Visscher from the University of Connecticut present a convincing answer to the puzzle: The Earth's early oxygen-producing microbes were breathers and photosynthesizers of arsenic, however poisonous to us that may be now.
Unassuming but remarkable microbial mats
Photosynthesis chiefly requires sunlight, water, and CO2. The CO2 gets broken down into carbon and oxygen — the plant uses some of this oxygen and releases the rest. Without oxygen molecules, though, how did this work?
There are known microbial mats today that live in oxygen-free environments, but they're not thought to be sufficiently like their ancestors to explain ancient photosynthesis in an oxygen-free environment.
There have been a few oxygen stand-ins proposed. Photosynthesis can work with iron molecules, but fossil-record evidence doesn't support that idea. Hydrogen and sulphur have also been proposed, though evidence for them is also lacking.
The spotlight began to shift to arsenic in the first decade of the millennium when arsenic-breathing microbial mats were discovered in two hypersaline California lakes, Searles Lake and Mono Lake. In 2014, Visscher and colleagues unearthed indications of arsenic-based photosynthesis, or "arsenotrophic," microbial mats deep in the fossil record of the Tumbiana Formation of Western Australia.
Still, given the ever-shifting geology of the planets, the fractured ancient fossil record makes definitive study of ancient arsenotrophic photosynthesis difficult. The fossil record can't identify the role of the arsenic it reveals: was it involved in photosynthesis or just a toxic chemical that happened to be there?
Then, last year, arsenic-breathing microorganisms were discovered in the Pacific Ocean. A sulphur bacterium, Ectothiorhodospira sp. was also recently found to be metabolizing arsenic into arsenite in Big Soda Lake in Nevada.
An ancient Earth environment, today
a Map of Northern Chile; b Detail of frame showing Laguna La Brava in the southern Atacama; c The channel showing the mats in purple; d Hand sample, cross-section; e Microscopic image of bacteria.
Credit: Visscher, et al./Communications Earth & Environment
The study reports on Visscher's discovery of a living microbial mat thriving in an arsenic environment in Laguna La Brava in the Atacama Desert in Chile. "We started working in Chile," Visscher tells UConn Today, "where I found a blood-red river. The red sediments are made up by anoxogenic photosynthetic bacteria. The water is very high in arsenic as well. The water that flows over the mats contains hydrogen sulfide that is volcanic in origin and it flows very rapidly over these mats. There is absolutely no oxygen."
The mats had not previously been studied, and the conditions in which they live are tantalizingly similar to those of early Earth. It's a high-altitude, permanently oxygen-free state with extreme temperature swings and lots of UV exposure.
The mats that somewhat resemble Nevada's purple Ectothiorhodospira sp. are going about their business of making carbonate deposits, forming new stromatolites. Most excitingly, those deposits contain evidence that the mats are metabolizing arsenic. The rushing waters surrounding the mats are also rich in hydrogen sulphide and arsenic.
Says Visscher, "I have been working with microbial mats for about 35 years or so. This is the only system on Earth where I could find a microbial mat that worked absolutely in the absence of oxygen."
Not that Earth is the only place where this could happen. Visscher notes that the equipment they used for studying the Laguna La Brava mats is not unlike the system aboard the Mars Perseverance Rover. "In looking for evidence of life on Mars, they will be looking at iron, and probably they should be looking at arsenic also."
How would the ability to genetically customize children change society? Sci-fi author Eugene Clark explores the future on our horizon in Volume I of the "Genetic Pressure" series.
- A new sci-fi book series called "Genetic Pressure" explores the scientific and moral implications of a world with a burgeoning designer baby industry.
- It's currently illegal to implant genetically edited human embryos in most nations, but designer babies may someday become widespread.
- While gene-editing technology could help humans eliminate genetic diseases, some in the scientific community fear it may also usher in a new era of eugenics.
Tribalism and discrimination<p>One question the "Genetic Pressure" series explores: What would tribalism and discrimination look like in a world with designer babies? As designer babies grow up, they could be noticeably different from other people, potentially being smarter, more attractive and healthier. This could breed resentment between the groups—as it does in the series.</p><p>"[Designer babies] slowly find that 'everyone else,' and even their own parents, becomes less and less tolerable," author Eugene Clark told Big Think. "Meanwhile, everyone else slowly feels threatened by the designer babies."</p><p>For example, one character in the series who was born a designer baby faces discrimination and harassment from "normal people"—they call her "soulless" and say she was "made in a factory," a "consumer product." </p><p>Would such divisions emerge in the real world? The answer may depend on who's able to afford designer baby services. If it's only the ultra-wealthy, then it's easy to imagine how being a designer baby could be seen by society as a kind of hyper-privilege, which designer babies would have to reckon with. </p><p>Even if people from all socioeconomic backgrounds can someday afford designer babies, people born designer babies may struggle with tough existential questions: Can they ever take full credit for things they achieve, or were they born with an unfair advantage? To what extent should they spend their lives helping the less fortunate? </p>
Sexuality dilemmas<p>Sexuality presents another set of thorny questions. If a designer baby industry someday allows people to optimize humans for attractiveness, designer babies could grow up to find themselves surrounded by ultra-attractive people. That may not sound like a big problem.</p><p>But consider that, if designer babies someday become the standard way to have children, there'd necessarily be a years-long gap in which only some people are having designer babies. Meanwhile, the rest of society would be having children the old-fashioned way. So, in terms of attractiveness, society could see increasingly apparent disparities in physical appearances between the two groups. "Normal people" could begin to seem increasingly ugly.</p><p>But ultra-attractive people who were born designer babies could face problems, too. One could be the loss of body image. </p><p>When designer babies grow up in the "Genetic Pressure" series, men look like all the other men, and women look like all the other women. This homogeneity of physical appearance occurs because parents of designer babies start following trends, all choosing similar traits for their children: tall, athletic build, olive skin, etc. </p><p>Sure, facial traits remain relatively unique, but everyone's more or less equally attractive. And this causes strange changes to sexual preferences.</p><p>"In a society of sexual equals, they start looking for other differentiators," he said, noting that violet-colored eyes become a rare trait that genetically engineered humans find especially attractive in the series.</p><p>But what about sexual relationships between genetically engineered humans and "normal" people? In the "Genetic Pressure" series, many "normal" people want to have kids with (or at least have sex with) genetically engineered humans. But a minority of engineered humans oppose breeding with "normal" people, and this leads to an ideology that considers engineered humans to be racially supreme. </p>
Regulating designer babies<p>On a policy level, there are many open questions about how governments might legislate a world with designer babies. But it's not totally new territory, considering the West's dark history of eugenics experiments.</p><p>In the 20th century, the U.S. conducted multiple eugenics programs, including immigration restrictions based on genetic inferiority and forced sterilizations. In 1927, for example, the Supreme Court ruled that forcibly sterilizing the mentally handicapped didn't violate the Constitution. Supreme Court Justice Oliver Wendall Holmes wrote, "… three generations of imbeciles are enough." </p><p>After the Holocaust, eugenics programs became increasingly taboo and regulated in the U.S. (though some states continued forced sterilizations <a href="https://www.uvm.edu/~lkaelber/eugenics/" target="_blank">into the 1970s</a>). In recent years, some policymakers and scientists have expressed concerns about how gene-editing technologies could reanimate the eugenics nightmares of the 20th century. </p><p>Currently, the U.S. doesn't explicitly ban human germline genetic editing on the federal level, but a combination of laws effectively render it <a href="https://academic.oup.com/jlb/advance-article/doi/10.1093/jlb/lsaa006/5841599#204481018" target="_blank" rel="noopener noreferrer">illegal to implant a genetically modified embryo</a>. Part of the reason is that scientists still aren't sure of the unintended consequences of new gene-editing technologies. </p><p>But there are also concerns that these technologies could usher in a new era of eugenics. After all, the function of a designer baby industry, like the one in the "Genetic Pressure" series, wouldn't necessarily be limited to eliminating genetic diseases; it could also work to increase the occurrence of "desirable" traits. </p><p>If the industry did that, it'd effectively signal that the <em>opposites of those traits are undesirable. </em>As the International Bioethics Committee <a href="https://academic.oup.com/jlb/advance-article/doi/10.1093/jlb/lsaa006/5841599#204481018" target="_blank" rel="noopener noreferrer">wrote</a>, this would "jeopardize the inherent and therefore equal dignity of all human beings and renew eugenics, disguised as the fulfillment of the wish for a better, improved life."</p><p><em>"Genetic Pressure Volume I: Baby Steps"</em><em> by Eugene Clark is <a href="http://bigth.ink/38VhJn3" target="_blank">available now.</a></em></p>
The father of all giant sea bugs was recently discovered off the coast of Java.
- A new species of isopod with a resemblance to a certain Sith lord was just discovered.
- It is the first known giant isopod from the Indian Ocean.
- The finding extends the list of giant isopods even further.
The ocean depths are home to many creatures that some consider to be unnatural.<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzU2NzY4My9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYxNTUwMzg0NX0.BTK3zVeXxoduyvXfsvp4QH40_9POsrgca_W5CQpjVtw/img.png?width=980" id="b6fb0" class="rm-shortcode" data-rm-shortcode-id="2739ec50d9f9a3bd0058f937b6d447ac" data-rm-shortcode-name="rebelmouse-image" data-width="1512" data-height="2224" />
What benefit does this find have for science? And is it as evil as it looks?<div class="rm-shortcode" data-media_id="7XqcvwWp" data-player_id="FvQKszTI" data-rm-shortcode-id="8506fcd195866131efb93525ae42dec4"> <div id="botr_7XqcvwWp_FvQKszTI_div" class="jwplayer-media" data-jwplayer-video-src="https://content.jwplatform.com/players/7XqcvwWp-FvQKszTI.js"> <img src="https://cdn.jwplayer.com/thumbs/7XqcvwWp-1920.jpg" class="jwplayer-media-preview" /> </div> <script src="https://content.jwplatform.com/players/7XqcvwWp-FvQKszTI.js"></script> </div> <p>The discovery of a new species is always a cause for celebration in zoology. That this is the discovery of an animal that inhabits the deeps of the sea, one of the least explored areas humans can get to, is the icing on the cake.</p><p>Helen Wong of the National University of Singapore, who co-authored the species' description, explained the importance of the discovery:</p><p>"The identification of this new species is an indication of just how little we know about the oceans. There is certainly more for us to explore in terms of biodiversity in the deep sea of our region." </p><p>The animal's visual similarity to Darth Vader is a result of its compound eyes and the curious shape of its <a href="https://lkcnhm.nus.edu.sg/research/sjades2018/" target="_blank" rel="noopener noreferrer dofollow" style="">head</a>. However, given the location of its discovery, the bottom of the remote seas, it may be associated with all manner of horrifically evil Elder Things and <a href="https://en.wikipedia.org/wiki/Cthulhu" target="_blank" rel="dofollow">Great Old Ones</a>. <em></em></p>
We look back at a year ravaged by a global pandemic, economic downturn, political turmoil and the ever-worsening climate crisis.
Billions are at risk of missing out on the digital leap forward, as growing disparities challenge the social fabric.
Image: Global Risks Report 2021<h3>Widespread effects</h3><p>"The immediate human and economic costs of COVID-19 are severe," the report says. "They threaten to scale back years of progress on reducing global poverty and inequality and further damage social cohesion and global cooperation."</p><p>For those reasons, the pandemic demonstrates why infectious diseases hits the top of the impact list. Not only has COVID-19 led to widespread loss of life, it is holding back economic development in some of the poorest parts of the world, while amplifying wealth inequalities across the globe.</p><p>At the same time, there are concerns the fight against the pandemic is taking resources away from other critical health challenges - including a <a href="https://www.weforum.org/agenda/2020/09/charts-covid19-malnutrition-educaion-mental-health-children-world/" target="_blank" rel="noopener noreferrer">disruption to measles vaccination programmes</a>.</p>
A new study explains how a chaotic region just outside a black hole's event horizon might provide a virtually endless supply of energy.
- In 1969, the physicist Roger Penrose first proposed a way in which it might be possible to extract energy from a black hole.
- A new study builds upon similar ideas to describe how chaotic magnetic activity in the ergosphere of a black hole may produce vast amounts of energy, which could potentially be harvested.
- The findings suggest that, in the very distant future, it may be possible for a civilization to survive by harnessing the energy of a black hole rather than a star.
The ergosphere<p>The ergosphere is a region just outside a black hole's event horizon, the boundary of a black hole beyond which nothing, not even light, can escape. But light and matter just outside the event horizon, in the ergosphere, would also be affected by the immense gravity of the black hole. Objects in this zone would spin in the same direction as the black hole at incredibly fast speeds, similar to objects floating around the center of a whirlpool.</p><p>The Penrose process states, in simple terms, that an object could enter the ergosphere and break into two pieces. One piece would head toward the event horizon, swallowed by the black hole. But if the other piece managed to escape the ergosphere, it could emerge with more energy than it entered with.</p><p>The movie "Interstellar" provides an example of the Penrose process. Facing a fuel shortage on a deep-space mission, the crew makes a last-ditch effort to return home by entering the ergosphere of a blackhole, ditching part of their spacecraft, and "slingshotting" away from the black hole with vast amounts of energy.</p><p>In a recent study published in the American Physical Society's <a href="https://journals.aps.org/prd/abstract/10.1103/PhysRevD.103.023014" target="_blank" style="">Physical Review D</a><em>, </em>physicists Luca Comisso and Felipe A. Asenjo used similar ideas to describe another way energy could be extracted from a black hole. The idea centers on the magnetic fields of black holes.</p><p style="margin-left: 20px;">"Black holes are commonly surrounded by a hot 'soup' of plasma particles that carry a magnetic field," Comisso, a research scientist at Columbia University and lead study author, told <a href="https://news.columbia.edu/energy-particles-magnetic-fields-black-holes" target="_blank" rel="noopener noreferrer">Columbia News</a>.</p>
Event Horizon Telescope Collaboration<p>While there might not be immediate applications for the theory, it could help scientists better understand and observe black holes. On an abstract level, the findings may expand the limits of what scientists imagine is possible in deep space.</p><p style="margin-left: 20px;">"Thousands or millions of years from now, humanity might be able to survive around a black hole without harnessing energy from stars," Comisso said. "It is essentially a technological problem. If we look at the physics, there is nothing that prevents it."</p>
A popular and longstanding wave of thought in psychology and psychotherapy is that diagnosis is not relevant for practitioners in those fields.