Biology – Page 7

AI used to design a multi-step enzyme that can digest some plastics

AI, biochemistry, Biology, catalysts, chemistry, Computer science, enzymes, Science / Mike M. / February 16, 2025

And it worked. Repeating the same process with an added PLACER screening step boosted the number of enzymes with catalytic activity by over three-fold.

Unfortunately, all of these enzymes stalled after a single reaction. It turns out they were much better at cleaving the ester, but they left one part of it chemically bonded to the enzyme. In other words, the enzymes acted like part of the reaction, not a catalyst. So the researchers started using PLACER to screen for structures that could adopt a key intermediate state of the reaction. This produced a much higher rate of reactive enzymes (18 percent of them cleaved the ester bond), and two—named “super” and “win”—could actually cycle through multiple rounds of reactions. The team had finally made an enzyme.

By adding additional rounds alternating between structure suggestions using RFDiffusion and screening using PLACER, the team saw the frequency of functional enzymes increase and eventually designed one that had an activity similar to some produced by actual living things. They also showed they could use the same process to design an esterase capable of digesting the bonds in PET, a common plastic.

If that sounds like a lot of work, it clearly was—designing enzymes, especially ones where we know of similar enzymes in living things, will remain a serious challenge. But at least much of it can be done on computers rather than requiring someone to order up the DNA that encodes the enzyme, getting bacteria to make it, and screening for activity. And despite the process involving references to known enzymes, the designed ones didn’t share a lot of sequences in common with them. That suggests there should be added flexibility if we want to design one that will react with esters that living things have never come across.

I’m curious about what might happen if we design an enzyme that is essential for survival, put it in bacteria, and then allow it to evolve for a while. I suspect life could find ways of improving on even our best designs.

Science, 2024. DOI: 10.1126/science.adu2454 (About DOIs).

AI used to design a multi-step enzyme that can digest some plastics Read More »

Parrots struggle when told to do something other than mimic their peers

animal behavior, Behavioral science, Biology, parrots, Science / Beth Washington / February 7, 2025

There have been many studies on the capability of non-human animals to mimic transitive actions—actions that have a purpose. Hardly any studies have shown that animals are also capable of intransitive actions. Even though intransitive actions have no particular purpose, imitating these non-conscious movements is still thought to help with socialization and strengthen bonds for both animals and humans.

Zoologist Esha Haldar and colleagues from the Comparative Cognition Research group worked with blue-throated macaws, which are critically endangered, at the Loro Parque Fundación in Tenerife. They trained the macaws to perform two intransitive actions, then set up a conflict: Two neighboring macaws were asked to do different actions.

What Haldar and her team found was that individual birds were more likely to perform the same intransitive action as a bird next to them, no matter what they’d been asked to do. This could mean that macaws possess mirror neurons, the same neurons that, in humans, fire when we are watching intransitive movements and cause us to imitate them (at least if these neurons function the way some think they do).

But it wasn’t on purpose

Parrots are already known for their mimicry of transitive actions, such as grabbing an object. Because they are highly social creatures with brains that are large relative to the size of their bodies, they made excellent subjects for a study that gauged how susceptible they were to copying intransitive actions.

Mirroring of intransitive actions, also called automatic imitation, can be measured with what’s called a stimulus-response-compatibility (SRC) test. These tests measure the response time between seeing an intransitive movement (the visual stimulus) and mimicking it (the action). A faster response time indicates a stronger reaction to the stimulus. They also measure the accuracy with which they reproduce the stimulus.

Until now, there have only been three studies that showed non-human animals are capable of copying intransitive actions, but the intransitive actions in these studies were all by-products of transitive actions. Only one of these focused on a parrot species. Haldar and her team would be the first to test directly for animal mimicry of intransitive actions.

Parrots struggle when told to do something other than mimic their peers Read More »

Bonobos recognize when humans are ignorant, try to help

Behavioral science, Biology, cooperation, Neuroscience, Science, theory of mind / Beth Washington / February 4, 2025

A lot of human society requires what’s called a “theory of mind”—the ability to infer the mental state of another person and adjust our actions based on what we expect they know and are thinking. We don’t always get this right—it’s easy to get confused about what someone else might be thinking—but we still rely on it to navigate through everything from complicated social situations to avoid bumping into people on the street.

There’s some mixed evidence that other animals have a limited theory of mind, but there are alternate interpretations for most of it. So two researchers at Johns Hopkins, Luke Townrow and Christopher Krupenye, came up with a way of testing whether some of our closest living relatives, the bonobos, could infer the state of mind of a human they were cooperating with. The work clearly showed that the bonobos could tell when their human partner was ignorant.

Now you see it…

The experimental approach is quite simple, and involves a setup familiar to street hustlers: a set of three cups, with a treat placed under one of them. Except in this case, there’s no sleight-of-hand in that the chimp can watch as one experimenter places the treat under a cup, and all of the cups remain stationary throughout the experiment.

To get the treat, however, requires the cooperation of a second human experimenter. That person has to identify the right cup, then give the treat under it to the bonobo. In some experiments, this human can watch the treat being hidden through a transparent partition, and so knows exactly where it is. In others, however, the partition is solid, leaving the human with no idea of which cup might be hiding the food.

This setup means that the bonobo will always know where the food is and will also know whether the human could potentially have the same knowledge.

The bonobos were first familiarized with the setup and got to experience their human partner taking the treat out from under the cup and giving it to them. Once they were familiar with the process, they watched the food being hidden without any partner present, which demonstrated they rarely took any food-directed actions without a good reason to do so. In contrast, when their human partner was present, they were about eight times more likely to point to the cup with the food under it.

Bonobos recognize when humans are ignorant, try to help Read More »

Let us spray: River dolphins launch pee streams into air

animal behavior, animal communication, animals, Biology, dolphins, Science / Mike M. / February 4, 2025

According to Amazonian folklore, the area’s male river dolphins are shapeshifters (encantade), transforming at night into handsome young men who seduce and impregnate human women. The legend’s origins may lie in the fact that dolphins have rather human-like genitalia. A group of Canadian biologists didn’t spot any suspicious shapeshifting behavior over the four years they spent monitoring a dolphin population in central Brazil, but they did document 36 cases of another human-like behavior: what appears to be some sort of cetacean pissing contest.

Specifically, the male dolphins rolled over onto their backs, displayed their male members, and launched a stream of urine as high as 3 feet into the air. This usually occurred when other males were around, who seemed fascinated in turn by the arching streams of pee, even chasing after them with their snouts. It’s possibly a form of chemical sensory communication and not merely a need to relieve themselves, according to the biologists, who described their findings in a paper published in the journal Behavioral Processes. As co-author Claryana Araújo-Wang of CetAsia Research Group in Ontario, Canada, told New Scientist, “We were really shocked, as it was something we had never seen before.”

Spraying urine is a common behavior in many animal species, used to mark territory, defend against predators, communicate with other members of one’s species, or as a means of mate selection since it has been suggested that the chemicals in the urine carry useful information about physical health or social dominance.

Let us spray: River dolphins launch pee streams into air Read More »

Stem cells used to partially repair damaged hearts

Biology, heart disease, heart musle, medicine, Science, stem cells / Shannon Garcia / January 29, 2025

When we developed the ability to convert various cells into a stem cell, it held the promise of an entirely new type of therapy. Rather than getting the body to try to fix itself with its cells or deal with the complications of organ transplants, we could convert a few adult cells to stem cells and induce them to form any tissue in the body. We could potentially repair or replace tissues with an effectively infinite supply of a patient’s own cells.

However, the Nobel Prize for induced stem cells was handed out over a decade ago, and the therapies have been slow to follow. But a group of German researchers is now describing tests in primates of a method of repairing the heart using new muscle generated from stem cells. The results are promising, if not yet providing everything that we might hope for. But they’ve been enough to start clinical trials, and similar results are being seen in humans.

Heart problems

The heart contains a lot of specialized tissues, including those that form blood vessels or specialize in conducting electrical signals. But the key to the heart is a form of specialized muscle cell, called a cardiomyocyte. Once the heart matures, the cardiomyocytes stop dividing, meaning that you end up with a fixed population. Any damage to the heart due to injury or infection does not get repaired, meaning damage will be cumulative.

This is especially problematic in cases of blocked blood vessels, which can repeatedly starve large areas of the heart of oxygen and nutrients, killing the cardiomyocytes there. This leads to a reduction in cardiac function and can ultimately result in death.

It turns out, however, that it’s relatively easy to convert induced pluripotent stem cells (IPSC, with pluripotent meaning they can form any cell type). So researchers tried injecting these stem-cell-derived cardiomyocytes into damaged hearts in experimental animals, in the hope that they would be incorporated into the damaged tissue. But these experiments didn’t always provide clear benefits to the animals.

Stem cells used to partially repair damaged hearts Read More »

Sleeping pills stop the brain’s system for cleaning out waste

Biology, brain, Features, neurobiology, nREM sleep, Science, sleeping pills / Beth Washington / January 20, 2025

Cleanup on aisle cerebellum

A specialized system sends pulses of pressure through the fluids in our brain.

Our bodies rely on their lymphatic system to drain excessive fluids and remove waste from tissues, feeding those back into the blood stream. It’s a complex yet efficient cleaning mechanism that works in every organ except the brain. “When cells are active, they produce waste metabolites, and this also happens in the brain. Since there are no lymphatic vessels in the brain, the question was what was it that cleaned the brain,” Natalie Hauglund, a neuroscientist at Oxford University who led a recent study on the brain-clearing mechanism, told Ars.

Earlier studies done mostly on mice discovered that the brain had a system that flushed its tissues with cerebrospinal fluid, which carried away waste products in a process called glymphatic clearance. “Scientists noticed that this only happened during sleep, but it was unknown what it was about sleep that initiated this cleaning process,” Hauglund explains.

Her study found the glymphatic clearance was mediated by a hormone called norepinephrine and happened almost exclusively during the NREM sleep phase. But it only worked when sleep was natural. Anesthesia and sleeping pills shut this process down nearly completely.

Taking it slowly

The glymphatic system in the brain was discovered back in 2013 by Dr. Maiken Nedergaard, a Danish neuroscientist and a coauthor of Hauglund’s paper. Since then, there have been numerous studies aimed at figuring out how it worked, but most of them had one problem: they were done on anesthetized mice.

“What makes anesthesia useful is that you can have a very controlled setting,” Hauglund says.

Most brain imaging techniques require a subject, an animal or a human, to be still. In mouse experiments, that meant immobilizing their heads so the research team could get clear scans. “But anesthesia also shuts down some of the mechanisms in the brain,” Hauglund argues.

So, her team designed a study to see how the brain-clearing mechanism works in mice that could move freely in their cages and sleep naturally whenever they felt like it. “It turned out that with the glymphatic system, we didn’t really see the full picture when we used anesthesia,” Hauglund says.

Looking into the brain of a mouse that runs around and wiggles during sleep, though, wasn’t easy. The team pulled it off by using a technique called flow fiber photometry which works by imaging fluids tagged with fluorescent markers using a probe implanted in the brain. So, the mice got the optical fibers implanted in their brains. Once that was done, the team put fluorescent tags in the mice’s blood, cerebrospinal fluid, and on the norepinephrine hormone. “Fluorescent molecules in the cerebrospinal fluid had one wavelength, blood had another wavelength, and norepinephrine had yet another wavelength,” Hauglund says.

This way, her team could get a fairly precise idea about the brain fluid dynamics when mice were awake and asleep. And it turned out that the glymphatic system basically turned brain tissues into a slowly moving pump.

Pumping up

“Norepinephrine is released from a small area of the brain in the brain stem,” Hauglund says. “It is mainly known as a response to stressful situations. For example, in fight or flight scenarios, you see norepinephrine levels increasing.” Its main effect is causing blood vessels to contract. Still, in more recent research, people found out that during sleep, norepinephrine is released in slow waves that roll over the brain roughly once a minute. This oscillatory norepinephrine release proved crucial to the operation of the glymphatic system.

“When we used the flow fiber photometry method to look into the brains of mice, we saw these slow waves of norepinephrine, but we also saw how it works in synchrony with fluctuation in the blood volume,” Hauglund says.

Every time the norepinephrine level went up, it caused the contraction of the blood vessels in the brain, and the blood volume went down. At the same time, the contraction increased the volume of the perivascular spaces around the blood vessels, which were immediately filled with the cerebrospinal fluid.

When the norepinephrine level went down, the process worked in reverse: the blood vessels dilated, letting the blood in and pushing the cerebrospinal fluid out. “What we found was that norepinephrine worked a little bit like a conductor of an orchestra and makes the blood and cerebrospinal fluid move in synchrony in these slow waves,” Hauglund says.

And because the study was designed to monitor this process in freely moving, undisturbed mice, the team learned exactly when all this was going on. When mice were awake, the norepinephrine levels were much higher but relatively steady. The team observed the opposite during the REM sleep phase, where the norepinephrine levels were consistently low. The oscillatory behavior was present exclusively during the NREM sleep phase.

So, the team wanted to check how the glymphatic clearance would work when they gave the mice zolpidem, a sleeping drug that had been proven to increase NREM sleep time. In theory, zolpidem should have boosted brain-clearing. But it turned it off instead.

Non-sleeping pills

“When we looked at the mice after giving them zolpidem, we saw they all fell asleep very quickly. That was expected—we take zolpidem because it makes it easier for us to sleep,” Hauglund says. “But then we saw those slow fluctuations in norepinephrine, blood volume, and cerebrospinal fluid almost completely stopped.”

No fluctuations meant the glymphatic system didn’t remove any waste. This was a serious issue, because one of the cellular waste products it is supposed to remove is amyloid beta, found in the brains of patients suffering from Alzheimer’s disease.

Hauglund speculates it could be possible zolpidem induces a state very similar to sleep but at the same time it shuts down important processes that happen during sleep. While heavy zolpidem use has been associated with increased risk of the Alzheimer disease, it is not clear if this increased risk was there because the drug was inhibiting oscillatory norepinephrine release in the brain. To better understand this, Hauglund wants to get a closer look into how the glymphatic system works in humans.

“We know we have the same wave-like fluid dynamics in the brain, so this could also drive the brain clearance in humans,” Haugland told Ars. “Still, it’s very hard to look at norepinephrine in the human brain because we need an invasive technique to get to the tissue.”

But she said norepinephrine levels in people can be estimated based on indirect clues. One of them is pupil dilation and contraction, which work in in synchrony with the norepinephrine levels. Another other clue may lay in microarousals—very brief, imperceivable awakenings which, Hauglund thinks, can be correlated with the brain clearing mechanism. “I am currently interested in this phenomenon […]. Right now we have no idea why microarousals are there or what function they have” Hauglund says.

But the last step she has on her roadmap is making better sleeping pills. “We need sleeping drugs that don’t have this inhibitory effect on the norepinephrine waves. If we can have a sleeping pill that helps people sleep without disrupting their sleep at the same time it will be very important,” Hauglund concludes.

Cell, 2025. DOI: 10.1016/j.cell.2024.11.027

Jacek Krywko is a freelance science and technology writer who covers space exploration, artificial intelligence research, computer science, and all sorts of engineering wizardry.

Sleeping pills stop the brain’s system for cleaning out waste Read More »

Peeing is contagious among chimps

animal behavior, animals, Biology, chimpanzees, Science, zoology / DJ Henderson / January 20, 2025

Those results supported the initial hypothesis that chimps tended to urinate in sync rather than randomly. Further analysis showed that the closer a chimp was to another peeing chimp, the more likely the probability of that chimp peeing as well—evidence of social contagion. Finally, Onishi et al. wanted to explore whether social relationships (like socially close pairs, evidenced by mutual grooming and similar behaviors) influenced contagious urination. The only social factor that proved relevant was dominance, with less-dominant chimps being more prone to contagious urination.

There may still be other factors influencing the behavior, and more experimental research is needed on potential sensory cues and social triggers in order to identify possible underlying mechanisms for the phenomenon. Furthermore, this study was conducted with a captive chimp population; to better understand potential evolutionary roots, there should be research on wild chimp populations, looking at possible links between contagious urination and factors like ranging patterns, territory use, and so forth.

“This was an unexpected and fascinating result, as it opens up multiple possibilities for interpretation,” said coauthor Shinya Yamamoto, also of Kyoto University. “For instance, it could reflect hidden leadership in synchronizing group activities, the reinforcement of social bonds, or attention bias among lower-ranking individuals. These findings raise intriguing questions about the social functions of this behavior.”

DOI: Current Biology, 2025. 10.1016/j.cub.2024.11.052 (About DOIs).

Peeing is contagious among chimps Read More »

Life is thriving in the subsurface depths of Earth

Biology, Ecology, life, Science / Shannon Garcia / January 20, 2025

Nitrospirota is an archaeal phylum that’s particularly common in the terrestrial subsurface. Some species of nitrospirota are capable of oxidizing ammonia, while others can reduce it to nitrite, which is used by phytoplankton and also defends against pathogens in the human stomach, mouth, and skin.

Proteobacteria is a bacterial phylum that’s especially abundant in the terrestrial and marine subsurface. Some proteobacteria live in deep ocean trenches, and oxidize carbon monoxide (which contributes to global warming and depletes ozone). Bacteria also common in the marine subsurface include Desulfobacteria and Methylomirabilota. Desulfobacteria reduce sulfates, and other sulfate-reducing bacterias have already shown they can be used to help clean up contaminated soil. Methylomirabilota help control methane levels in the atmosphere by oxidizing methane.

Something unexpected that caught Ruff’s attention was how total diversity went up with depth. This was surprising because less energy is available at deeper levels of the subsurface. For archaea, diversity went up with the increase in depth in terrestrial environments but not marine environments. The same happened with bacteria, except in marine instead of terrestrial environments.

Much of what lies far below our feet still eludes us. Ruff suggests that single-cell microbes in even deeper, yet unexplored levels of the subsurface may have adapted to the absence of energy by slowing down their metabolisms so drastically that it could take decades, even centuries, for them to divide just once.

If there really are microbes that manage to live longer than humans with this survival tactic, it is possible similar species might be hiding on planets such as Mars, where the surface has long been blasted by radiation.

“Understanding deep life on Earth could be a model for discovering if there was life on Mars, and if it has survived,” Ruff said in a press release.

Maybe future technology could retrieve samples several kilometers below the Martian surface. Until then, keep digging.

Science Advances, 2024. DOI: 10.1126/sciadv.adq0645

Life is thriving in the subsurface depths of Earth Read More »

US to start nationwide testing for H5N1 flu virus in milk supply

Biology, bird flu, Flu virus, H5N1, health, Infectious disease, medicine, Science / DJ Henderson / December 6, 2024

So, the ultimate goal of the USDA is to eliminate cattle as a reservoir. When the Agency announced it was planning for this program, it noted that there were two candidate vaccines in trials. Until those are validated, it plans to use the standard playbook for handling emerging infections: contact tracing and isolation. And it has the ability to compel cattle and their owners to be more cooperative than the human population turned out to be.

The five-step plan

The USDA refers to isolation and contact tracing as Stage 3 of a five-stage plan for controlling H5N1 in cattle, with the two earlier stages being the mandatory sampling and testing, meant to be handled on a state-by-state basis. Following the successful containment of the virus in a state, the USDA will move on to batch sampling to ensure each state remains virus-free. This is essential, given that we don’t have a clear picture of how many times the virus has jumped from its normal reservoir in birds into the cattle population.

That makes it possible that reaching Stage 5, which the USDA terms “Demonstrating Freedom from H5 in US Dairy Cattle,” will turn out to be impossible. Dairy cattle are likely to have daily contact with birds, and it may be that the virus will be regularly re-introduced into the population, leaving containment as the only option until the vaccines are ready.

Testing will initially focus primarily on states where cattle-to-human transmission is known to have occurred or the virus is known to be present: California, Colorado, Michigan, Mississippi, Oregon, and Pennsylvania. If you wish to track the progress of the USDA’s efforts, it will be posting weekly updates.

US to start nationwide testing for H5N1 flu virus in milk supply Read More »

Lizards and snakes are 35 million years older than we thought

Biology, fossils, lizards, paleontology, reptiles, Science / 9u50fv / December 6, 2024

Lizards are ancient creatures. They were around before the dinosaurs and persisted long after dinosaurs went extinct. We’ve now found they are 35 million years older than we thought they were.

Cryptovaranoides microlanius was a tiny lizard that skittered around what is now southern England during the late Triassic, around 205 million years ago. It likely snapped up insects in its razor teeth (its name means “hidden lizard, small butcher”). But it wasn’t always considered a lizard. Previously, a group of researchers who studied the first fossil of the creature, or holotype, concluded that it was an archosaur, part of a group that includes the extinct dinosaurs and pterosaurs along with extant crocodilians and birds.

Now, another research team from the University of Bristol has analyzed that fossil and determined that Cryptovaranoides is not an archosaur but a lepidosaur, part of a larger order of reptiles that includes squamates, the reptile group that encompasses modern snakes and lizards. It is now also the oldest known squamate.

The misunderstandings about this species all come down to features in its bones that are squamate apomorphies. These are traits unique to squamates that were not present in their ancestral form, but evolved later. Certain forelimb bones, skull bones, jawbones, and even teeth of Cryptovaranoides share characteristics with those from both modern and extinct lizards.

Wait, what is that thing?

So what does the new team argue that the previous team that studied Cryptovaranoides gets wrong? The new paper argues that the interpretation of a few bones in particular stand out, especially the humerus and radius.

In the humerus of this lizard, structures called the ectepicondylar and entepicondylar foramina, along with the radial condyle, were either not considered or may have been misinterpreted. The entepicondylar foramen is an opening in the far end of the humerus, which is an upper arm bone in humans and upper forelimb bone in lizards. The ectepicondylar foramen is a structure on the outer side of the humerus where the extensor muscles attach, helping a lizard bend and straighten its legs. Both features are “often regarded as key lepidosaur and squamate characteristics,” the Bristol research team said in a study recently published in Royal Society Open Science.

Lizards and snakes are 35 million years older than we thought Read More »

Researchers finally identify the ocean’s “mystery mollusk”

Biology, marine biology, phylogenetic, Science, Weird / Mike M. / December 2, 2024

Some of the most bizarre lifeforms on Earth lurk in the deeper realms of the ocean. There was so little known about one of these creatures that it took 20 years just to figure out what exactly it was. Things only got weirder from there.

The organism’s distinctive, glowing presence was observed by multiple deep-sea missions between 2000 to 2021 but was simply referred to as “mystery mollusk.” A team of Monterey Bay Aquarium Research Institute (MBARI) researchers has now reviewed extensive footage of past mystery mollusk sightings and used MBARI’s remotely operated vehicles (ROVs) to observe it and collect samples. They’ve given it a name and have finally confirmed that it is a nudibranch—the first and only nudibranch known to live at such depths.

Bathydevius caudactylus, as this nudibranch is now called, lives 1,000–4,000 meters (3,300–13,100 feet) deep in the ocean’s bathypelagic or midnight zone. It moves like a jellyfish, eats like a Venus flytrap, and is bioluminescent, and its genes are distinct enough for it to be classified as the first member of a new phylogenetic family.

“Anatomy, diet, behavior, bioluminescence, and habitat distinguish this surprising nudibranch from all previously described species, and genetic evidence supports its placement in a new family,” the MBARI research team said in a study recently published in Deep Sea Research.

Is that a…?

Nudibranchs are gastropods, which literally translates to “stomach foot” since the “foot” they crawl around on when not swimming is right below their guts. They are part of a larger group that includes terrestrial and aquatic snails and slugs. B. caudactylus, however, seems to get around more like a jellyfish than a sea slug. It mostly swims using an oral hood that opens and closes to propel itself backward through the water in a manner similar to many jellyfish.

The hood of B. caudactylus can also act something like a Venus flytrap. While it is not a hinged structure like the leaves of the plant, it is used to trap prey. Typically small crustaceans, the prey are then pushed to the mouth at the back of the hood.

The mystery mollusk.

The nudibranch also seems to have a unique way of avoiding becoming food itself. Projections at the end of its tail, known as dactyls, can detach if needed, much like the tails of some lizard species. The MBARI team thinks that these dactyls are possibly a lure meant to trick predators while the nudibranch swims away. They later regenerate.

Researchers finally identify the ocean’s “mystery mollusk” Read More »

How should we treat beings that might be sentient?

Biology, consciousness, ethics, neurobiology, Science, sentience / Beth Washington / November 30, 2024

Being aware of the maybe self-aware

A book argues that we’ve not thought enough about things that might think.

What rights should a creature with ambiguous self-awareness, like an octopus, be granted. Credit: A. Martin UW Photography

If you aren’t yet worried about the multitude of ways you inadvertently inflict suffering onto other living creatures, you will be after reading The Edge of Sentience by Jonathan Birch. And for good reason. Birch, a Professor of Philosophy at the London College of Economics and Political Science, was one of a team of experts chosen by the UK government to establish the Animal Welfare Act (or Sentience Act) in 2022—a law that protects animals whose sentience status is unclear.

According to Birch, even insects may possess sentience, which he defines as the capacity to have valenced experiences, or experiences that feel good or bad. At the very least, Birch explains, insects (as well as all vertebrates and a selection of invertebrates) are sentience candidates: animals that may be conscious and, until proven otherwise, should be regarded as such.

Although it might be a stretch to wrap our mammalian minds around insect sentience, it is not difficult to imagine that fellow vertebrates have the capacity to experience life, nor does it come as a surprise that even some invertebrates, such as octopuses and other cephalopod mollusks (squid, cuttlefish, and nautilus) qualify for sentience candidature. In fact, one species of octopus, Octopus vulgaris, has been protected by the UK’s Animal Scientific Procedures Act (ASPA) since 1986, which illustrates how long we have been aware of the possibility that invertebrates might be capable of experiencing valenced states of awareness, such as contentment, fear, pleasure, and pain.

A framework for fence-sitters

Non-human animals, of course, are not the only beings with an ambiguous sentience stature that poses complicated questions. Birch discusses people with disorders of consciousness, embryos and fetuses, neural organoids (brain tissue grown in a dish), and even “AI technologies that reproduce brain functions and/or mimic human behavior,” all of which share the unenviable position of being perched on the edge of sentience—a place where it is excruciatingly unclear whether or not these individuals are capable of conscious experience.

What’s needed, Birch argues, when faced with such staggering uncertainty about the sentience stature of other beings, is a precautionary framework that outlines best practices for decision-making regarding their care. And in The Edge of Sentience, he provides exactly that, in meticulous, orderly detail.

Over more than 300 pages, he outlines three fundamental framework principles and 26 specific case proposals about how to handle complex situations related to the care and treatment of sentience-edgers. For example, Proposal 2 cautions that “a patient with a prolonged disorder of consciousness should not be assumed incapable of experience” and suggests that medical decisions made on their behalf cautiously presume they are capable of feeling pain. Proposal 16 warns about conflating brain size, intelligence, and sentience, and recommends decoupling the three so that we do not incorrectly assume that small-brained animals are incapable of conscious experience.

Surgeries and stem cells

Be forewarned, some topics in The Edge of Sentience are difficult. For example, Chapter 10 covers embryos and fetuses. In the 1980s, Birch shares, it was common practice to not use anesthesia on newborn babies or fetuses when performing surgery. Why? Because whether or not newborns and fetuses experience pain was up for debate. Rather than put newborns and fetuses through the risks associated with anesthesia, it was accepted practice to give them a paralytic (which prevents all movement) and carry on with invasive procedures, up to and including heart surgery.

After parents raised alarms over the devastating outcomes of this practice, such as infant mortality, it was eventually changed. Birch’s takeaway message is clear: When in doubt about the sentience stature of a living being, we should probably assume it is capable of experiencing pain and take all necessary precautions to prevent it from suffering. To presume the opposite can be unethical.

This guidance is repeated throughout the book. Neural organoids, discussed in Chapter 11, are mini-models of brains developed from stem cells. The potential for scientists to use neural organoids to unravel the mechanisms of debilitating neurological conditions—and to avoid invasive animal research while doing so—is immense. It is also ethical, Birch posits, since studying organoids lessens the suffering of research animals. However, we don’t yet know whether or not neural tissue grown in a dish has the potential to develop sentience, so he argues that we need to develop a precautionary approach that balances the benefits of reduced animal research against the risk that neural organoids are capable of being sentient.

A four-pronged test

Along this same line, Birch says, all welfare decisions regarding sentience-edgers require an assessment of proportionality. We must balance the nature of a given proposed risk to a sentience candidate with potential harms that could result if nothing is done to minimize the risk. To do this, he suggests testing four criteria: permissibility-in-principle, adequacy, reasonable necessity, and consistency. Birch refers to this assessment process as PARC, and deep dives into its implementation in chapter eight.

When applying the PARC criteria, one begins by testing permissibility-in-principle: whether or not the proposed response to a risk is ethically permissible. To illustrate this, Birch poses a hypothetical question: would it be ethically permissible to mandate vaccination in response to a pandemic? If a panel of citizens were in charge of answering this question, they might say “no,” because forcing people to be vaccinated feels unethical. Yet, when faced with the same question, a panel of experts might say “yes,” because allowing people to die who could be saved by vaccination also feels unethical. Gauging permissibility-in-principle, therefore, entails careful consideration of the likely possible outcomes of a proposed response. If an outcome is deemed ethical, it is permissible.

Next, the adequacy of a proposed response must be tested. A proportionate response to a risk must do enough to lessen the risk. This means the risk must be reduced to “an acceptable level” or, if that’s not possible, a response should “deliver the best level of risk reduction that can be achieved” via an ethically permissible option.

The third test is reasonable necessity. A proposed response to a risk must not overshoot—it should not go beyond what is reasonably necessary to reduce risk, in terms of either cost or imposed harm. And last, consistency should be considered. The example Birch presents is animal welfare policy. He suggests we should always “aim for taxonomic consistency: our treatment of one group of animals (e.g., vertebrates) should be consistent with our treatment of another (e.g., invertebrates).”

The Edge of Sentience, as a whole, is a dense text overflowing with philosophical rhetoric. Yet this rhetoric plays a crucial role in the storytelling: it is the backbone for Birch’s clear and organized conclusions, and it serves as a jumping-off point for the logical progression of his arguments. Much like “I think, therefore I am” gave René Descartes a foundation upon which to build his idea of substance dualism, Birch uses the fundamental position that humans should not inflict gratuitous suffering onto fellow creatures as a base upon which to build his precautionary framework.

For curious readers who would prefer not to wade too deeply into meaty philosophical concepts, Birch generously provides a shortcut to his conclusions: a cheat sheet of his framework principles and special case proposals is presented at the front of the book.

Birch’s ultimate message in The Edge of Sentience is that a massive shift in how we view beings with a questionable sentience status should be made. And we should ideally make this change now, rather than waiting for scientific research to infallibly determine who and what is sentient. Birch argues that one way that citizens and policy-makers can begin this process is by adopting the following decision-making framework: always avoid inflicting gratuitous suffering on sentience candidates; take precautions when making decisions regarding a sentience candidate; and make proportional decisions about the care of sentience candidates that are “informed, democratic and inclusive.”

You might be tempted to shake your head at Birch’s confidence in humanity. No matter how deeply you agree with his stance of doing no harm, it’s hard to have confidence in humanity given our track record of not making big changes for the benefit of living creatures, even when said creatures includes our own species (cue in global warming here). It seems excruciatingly unlikely that the entire world will adopt Birch’s rational, thoughtful, comprehensive plan for reducing the suffering of all potentially sentient creatures. Yet Birch, a philosopher at heart, ignores human history and maintains a tone of articulate, patient optimism. He clearly believes in us—he knows we can do better—and he offers to hold our hands and walk us through the steps to do so.

Lindsey Laughlin is a science writer and freelance journalist who lives in Portland, Oregon, with her husband and four children. She earned her BS from UC Davis with majors in physics, neuroscience, and philosophy.

How should we treat beings that might be sentient? Read More »