Biology

we-probably-inherited-our-joints-from…-a-fish

We probably inherited our joints from… a fish

Biology, developmental biology, evolution, joints, paleontology, Science, synovial joints / /

What do we have in common with fish, besides being vertebrates? The types of joints we (and most vertebrates) share most likely originated from the same common ancestor. But it’s not a feature that we share with all vertebrates.

Humans, other land vertebrates, and jawed fish have synovial joints. The lubricated cavity within these joints makes them more mobile and stable because it allows for bones or cartilage to slide against each other without friction, which facilitates movement.

The origin of these joints was uncertain. Now, biologist Neelima Sharma of the University of Chicago and her colleagues have taken a look at which fish form this type of joint. Synovial joints are known to be present in jawed but not jawless fish. This left the question of whether they are just a feature of bony skeletons in general or if they are also found in fish with cartilaginous skeletons, such as sharks and skates (there are no land animals with cartilaginous skeletons).

As Sharma and her team found, cartilaginous fish with jaws, such as the skate embryos they studied, do develop these joints, while jawless fish, such as lampreys and hagfish, lack them.

So what could this mean? If jawed fish have synovial joints in common with all jawed vertebrates, including us, it must have evolved in our shared ancestor.

Something fishy in our past

While the common ancestor of vertebrates with synovial joints is still a mystery, the oldest specimen with evidence of these joints is Bothriolepis canadensis, a fish that lived about 387 to 360 million years ago during the Middle to Late Devonian period.

When using CT scanning to study a Bothriolepis fossil, Sharma observed a joint cavity between the shoulder and pectoral fin. Whether the cavity was filled with synovial fluid or cartilage is impossible to tell, but either way, she thinks it appears to have functioned like a synovial joint would. Fossils of early jawless fish, in contrast, lack any signs of synovial joints.

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“infantile-amnesia”-occurs-despite-babies-showing-memory-activity

“Infantile amnesia” occurs despite babies showing memory activity

Biology, infantile amnesia, memory, neurobiology, Science / /

For many of us, memories of our childhood have become a bit hazy, if not vanishing entirely. But nobody really remembers much before the age of 4, because nearly all humans experience what’s termed “infantile amnesia,” in which memories that might have formed before that age seemingly vanish as we move through adolescence. And it’s not just us; the phenomenon appears to occur in a number of our fellow mammals.

The simplest explanation for this would be that the systems that form long-term memories are simply immature and don’t start working effectively until children hit the age of 4. But a recent animal experiment suggests that the situation in mice is more complex: the memories are there, they’re just not normally accessible, although they can be re-activated. Now, a study that put human infants in an MRI tube suggests that memory activity starts by the age of 1, suggesting that the results in mice may apply to us.

Less than total recall

Mice are one of the species that we know experience infantile amnesia. And, thanks to over a century of research on mice, we have some sophisticated genetic tools that allow us to explore what’s actually involved in the apparent absence of the animals’ earliest memories.

A paper that came out last year describes a series of experiments that start by having very young mice learn to associate seeing a light come on with receiving a mild shock. If nothing else is done with those mice, that association will apparently be forgotten later in life due to infantile amnesia.

But in this case, the researchers could do something. Neural activity normally results in the activation of a set of genes. In these mice, the researchers engineered it so one of the genes that gets activated encodes a protein that can modify DNA. When this protein is made, it results in permanent changes to a second gene that was inserted in the animal’s DNA. Once activated through this process, the gene leads to the production of a light-activated ion channel.

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brains-of-parrots,-unlike-songbirds,-use-human-like-vocal-control

Brains of parrots, unlike songbirds, use human-like vocal control

Biology, brain, brain implants, language, neurobiology, Science, vocal control / /

Due to past work, we’ve already identified the brain structure that controls the activity of the key vocal organ, the syrinx, located in the bird’s throat. The new study, done by Zetian Yang and Michael Long of New York University, managed to place fine electrodes into this area of the brain in both species and track the activity of neurons there while the birds were awake and going about normal activities. This allowed them to associate neural activity with any vocalizations made by the birds. For the budgerigars, they had an average of over 1,000 calls from each of the four birds carrying the implanted electrodes.

For the zebra finch, neural activity during song production showed a pattern that was based on timing; the same neurons tended to be most active at the same point in the song. You can think of this as a bit like a player piano central organizing principle, timing when different notes should be played. “Different configurations [of neurons] are active at different moments, representing an evolving population ‘barcode,’” as Yang and Long describe this pattern.

That is not at all what was seen with the budgerigars. Here, instead, they saw patterns where the same populations of neurons tended to be active when the bird was producing a similar sound. They broke the warbles down into parts that they characterized on a scale that ranged from harmonic to noisy. They found that the groups of neurons tended to be more active whenever the warble was harmonic, and different groups tended to spike when it got noisy. Those observations led them to identify a third population, which was active whenever the budgerigars produced a low-frequency sound.

In addition, Yang and Long analyzed the pitch of the vocalizations. Only about half of the neurons in the relevant region of the brain were linked to pitch. However, the half that was linked had small groups of neurons that fired during the production of a relatively narrow range of pitches. They could use the activity of as few as five individual neurons and accurately predict the pitch of the vocalizations at the time.

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researchers-engineer-bacteria-to-produce-plastics

Researchers engineer bacteria to produce plastics

biochemistry, bioengineering, Biology, chemistry, plastics, Science / /

Image of a series of chemical reactions, with enzymes driving each step forward.

One of the enzymes used in this system takes an amino acid (left) and links it to Coenzyme A. The second takes these items and links them into a polymer. Credit: Chae et. al.

Normally, PHA synthase forms links between molecules that run through an oxygen atom. But it’s also possible to form a related chemical link that instead runs through a nitrogen atom, like those found on amino acids. There were no known enzymes, however, that catalyze these reactions. So, the researchers decided to test whether any existing enzymes could be induced to do something they don’t normally do.

The researchers started with an enzyme from Clostridium that links chemicals to Coenzyme A that has a reputation for not being picky about the chemicals it interacts with. This worked reasonably well at linking amino acids to Coenzyme A. For linking the amino acids together, they used an enzyme from Pseudomonas that had four different mutations that expanded the range of molecules it would use as reaction materials. Used in a test tube, the system worked: Amino acids were linked together in a polymer.

The question was whether it would work in cells. Unfortunately, one of the two enzymes turns out to be mildly toxic to E. coli, slowing its growth. So, the researchers evolved a strain of E. coli that could tolerate the protein. With both of these two proteins, the cells produced small amounts of an amino acid polymer. If they added an excess of an amino acid to the media the cells were growing in, the polymer would be biased toward incorporating that amino acid.

Boosting polymer production

However, the yield of the polymer by weight of bacteria was fairly low. “It was reasoned that these [amino acids] might be more efficiently incorporated into the polymer if generated within the cells from a suitable carbon source,” the researchers write. So, the researchers put in extra copies of the genes needed to produce one specific amino acid (lysine). That worked, producing more polymer, with a higher percentage of the polymer being lysine.

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a-“biohybrid”-robotic-hand-built-using-real-human-muscle-cells

A “biohybrid” robotic hand built using real human muscle cells

Biology, Cyborg, robotics, Science / /

Biohybrid robots work by combining biological components like muscles, plant material, and even fungi with non-biological materials. While we are pretty good at making the non-biological parts work, we’ve always had a problem with keeping the organic components alive and well. This is why machines driven by biological muscles have always been rather small and simple—up to a couple centimeters long and typically with only a single actuating joint.

“Scaling up biohybrid robots has been difficult due to the weak contractile force of lab-grown muscles, the risk of necrosis in thick muscle tissues, and the challenge of integrating biological actuators with artificial structures,” says Shoji Takeuchi, a professor at the Tokyo University, Japan. Takeuchi led a research team that built a full-size, 18 centimeter-long biohybrid human-like hand with all five fingers driven by lab-grown human muscles.

Keeping the muscles alive

Out of all the roadblocks that keep us from building large-scale biohybrid robots, necrosis has probably been the most difficult to overcome. Growing muscles in a lab usually means a liquid medium to supply nutrients and oxygen to muscle cells seeded on petri dishes or applied to gel scaffoldings. Since these cultured muscles are small and ideally flat, nutrients and oxygen from the medium can easily reach every cell in the growing culture.

When we try to make the muscles thicker and therefore more powerful, cells buried deeper in those thicker structures are cut off from nutrients and oxygen, so they die, undergoing necrosis. In living organisms, this problem is solved by the vascular network. But building artificial vascular networks in lab-grown muscles is still something we can’t do very well. So, Takeuchi and his team had to find their way around the necrosis problem. Their solution was sushi rolling.

The team started by growing thin, flat muscle fibers arranged side by side on a petri dish. This gave all the cells access to nutrients and oxygen, so the muscles turned out robust and healthy. Once all the fibers were grown, Takeuchi and his colleagues rolled them into tubes called MuMuTAs (multiple muscle tissue actuators) like they were preparing sushi rolls. “MuMuTAs were created by culturing thin muscle sheets and rolling them into cylindrical bundles to optimize contractility while maintaining oxygen diffusion,” Takeuchi explains.

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small-charges-in-water-spray-can-trigger-the-formation-of-key-biochemicals

Small charges in water spray can trigger the formation of key biochemicals

biochemistry, Biology, chemistry, origin of life, Physics, Science / /

Once his team nailed how droplets become electrically charged and how the micro-lightning phenomenon works, they recreated the Miller-Urey experiment. Only without the spark plugs.

Ingredients of life

After micro-lightnings started jumping between droplets in a mixture of gases similar to that used by Miller and Urey, the team examined their chemical composition with a mass spectrometer. They confirmed glycine, uracil, urea, cyanoethylene, and lots of other chemical compounds were made. “Micro-lightnings made all organic molecules observed previously in the Miller-Urey experiment without any external voltage applied,” Zare claims.

But does it really bring us any closer to explaining the beginnings of life? After all, Miller and Urey already demonstrated those molecules could be produced by electrical discharges in a primordial Earth’s atmosphere—does it matter all that much where those discharges came from?  Zare argues that it does.

“Lightning is intermittent, so it would be hard for these molecules to concentrate. But if you look at waves crashing into rocks, you can think the spray would easily go into the crevices in these rocks,” Zare suggests. He suggests that the water in these crevices would evaporate, new spray would enter and evaporate again and again. The cyclic drying would allow the chemical precursors to build into more complex molecules. “When you go through such a dry cycle, it causes polymerization, which is how you make DNA,” Zare argues. Since sources of spray were likely common on the early Earth, Zare thinks this process could produce far more organic chemicals than potential alternatives like lightning strikes, hydrothermal vents, or impacting comets.

But even if micro-lightning really produced the basic building blocks of life on Earth, we’re still not sure how those combined into living organisms. “We did not make life. We just demonstrated a possible mechanism that gives us some chemical compounds you find in life,” Zare says. “It’s very important to have a lot of humility with this stuff.”

Science Advances, 2025.  DOI: 10.1126/sciadv.adt8979

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in-one-dog-breed,-selection-for-utility-may-have-selected-for-obesity

In one dog breed, selection for utility may have selected for obesity

behavior, Biology, Dogs, Genetics, Labrador retriever, Science / /

High-risk Labradors also tended to pester their owners for food more often. Dogs with low genetic risk scores, on the other hand, stayed slim regardless of whether the owners paid attention to how and whether they were fed or not.

But other findings proved less obvious. “We’ve long known chocolate-colored Labradors are prone to being overweight, and I’ve often heard people say that’s because they’re really popular as pets for young families with toddlers that throw food on the floor all the time and where dogs are just not given that much attention,” Raffan says. Her team’s data showed that chocolate Labradors actually had a much higher genetic obesity risk than yellow or black ones

Some of the Labradors particularly prone to obesity, the study found, were guide dogs, which were included in the initial group. Training a guide dog in the UK usually takes around two years, during which the dogs learn multiple skills, like avoiding obstacles, stopping at curbs, navigating complex environments, and responding to emergency scenarios. Not all dogs are able to successfully finish this training, which is why guide dogs are often selectively bred with other guide dogs in the hope their offspring would have a better chance at making it through the same training.

But it seems that this selective breeding among guide dogs might have had unexpected consequences. “Our results raise the intriguing possibility that we may have inadvertently selected dogs prone to obesity, dogs that really like their food, because that makes them a little bit more trainable. They would do anything for a biscuit,” Raffan says.

The study also found that genes responsible for obesity in dogs are also responsible for obesity in humans. “The impact high genetic risk has on dogs leads to increased appetite. It makes them more interested in food,” Raffan claims. “Exactly the same is true in humans. If you’re at high genetic risk you aren’t inherently lazy or rubbish about overeating—it’s just you are more interested in food and get more reward from it.”

Science, 2025.  DOI: 10.1126/science.ads2145

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how-whale-urine-benefits-the-ocean-ecosystem

How whale urine benefits the ocean ecosystem

Biology, Ecology, marine animals, marine ecology, Science, whales / /

A “great whale conveyor belt”

illustration showing how whale urine spreads throughout the ocean ecosystem

Credit: A. Boersma

Migrating whales typically gorge in summers at higher latitudes to build up energy reserves to make the long migration to lower latitudes. It’s still unclear exactly why the whales migrate, but it’s likely that pregnant females in particular find it more beneficial to give birth and nurse their young in warm, shallow, sheltered areas—perhaps to protect their offspring from predators like killer whales. Warmer waters also keep the whale calves warm as they gradually develop their insulating layers of blubber. Some scientists think that whales might also migrate to molt their skin in those same warm, shallow waters.

Roman et al. examined publicly available spatial data for whale feeding and breeding grounds, augmented with sightings from airplane and ship surveys to fill in gaps in the data, then fed that data into their models for calculating nutrient transport. They focused on six species known to migrate seasonally over long distances from higher latitudes to lower latitudes: blue whales, fin whales, gray whales, humpback whales, and North Atlantic and southern right whales.

They found that whales can transport some 4,000 tons of nitrogen each year during their migrations, along with 45,000 tons of biomass—and those numbers could have been three times larger in earlier eras before industrial whaling depleted populations. “We call it the ‘great whale conveyor belt,’” Roman said. “It can also be thought of as a funnel, because whales feed over large areas, but they need to be in a relatively confined space to find a mate, breed, and give birth. At first, the calves don’t have the energy to travel long distances like the moms can.” The study did not include any effects from whales releasing feces or sloughing their skin, which would also contribute to the overall nutrient flux.

“Because of their size, whales are able to do things that no other animal does. They’re living life on a different scale,” said co-author Andrew Pershing, an oceanographer at the nonprofit organization Climate Central. “Nutrients are coming in from outside—and not from a river, but by these migrating animals. It’s super-cool, and changes how we think about ecosystems in the ocean. We don’t think of animals other than humans having an impact on a planetary scale, but the whales really do.” 

Nature Communications, 2025. DOI: 10.1038/s41467-025-56123-2  (About DOIs).

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“wooly-mice”-a-test-run-for-mammoth-gene-editing

“Wooly mice” a test run for mammoth gene editing

Biology, de-extinction, fur, gene editing, Genetics, mammoths, Mice, Science / /

On Tuesday, the team behind the plan to bring mammoth-like animals back to the tundra announced the creation of what it is calling wooly mice, which have long fur reminiscent of the woolly mammoth. The long fur was created through the simultaneous editing of as many as seven genes, all with a known connection to hair growth, color, and/or texture.

But don’t think that this is a sort of mouse-mammoth hybrid. Most of the genetic changes were first identified in mice, not mammoths. So, the focus is on the fact that the team could do simultaneous editing of multiple genes—something that they’ll need to be able to do to get a considerable number of mammoth-like changes into the elephant genome.

Of mice and mammoths

The team at Colossal Biosciences has started a number of de-extinction projects, including the dodo and thylacine, but its flagship project is the mammoth. In all of these cases, the plan is to take stem cells from a closely related species that has not gone extinct, and edit a series of changes based on the corresponding genomes of the deceased species. In the case of the mammoth, that means the elephant.

But the elephant poses a large number of challenges, as the draft paper that describes the new mice acknowledges. “The 22-month gestation period of elephants and their extended reproductive timeline make rapid experimental assessment impractical,” the researchers acknowledge. “Further, ethical considerations regarding the experimental manipulation of elephants, an endangered species with complex social structures and high cognitive capabilities, necessitate alternative approaches for functional testing.”

So, they turned to a species that has been used for genetic experiments for over a century: the mouse. We can do all sorts of genetic manipulations in mice, and have ways of using embryonic stem cells to get those manipulations passed on to a new generation of mice.

For testing purposes, the mouse also has a very significant advantage: mutations that change its fur are easy to spot. Over the century-plus that we’ve been using mice for research, people have noticed and observed a huge variety of mutations that affect their fur, altering color, texture, and length. In many of these cases, the changes in the DNA that cause these changes have been identified.

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an-small-microbial-ecosystem-has-formed-on-the-international-space-station

An small microbial ecosystem has formed on the International Space Station

Biology, Ecology, international space station, microbiome, Science / /

“One of the more similar environments to the ISS was in the isolation dorms on the UCSD campus during the COVID-19 pandemic. All surfaces were continuously sterilized, so that microbial signatures would be erased by the time another person would show up,” Benitez said. So, one of the first solutions to the ISS microbial diversity problem he and his colleagues suggested was that they perhaps should ease up on sterilizing the station so much.

“The extensive use of disinfection chemicals might not be the best approach to maintaining a healthy microbial environment, although there is certainly plenty of research to be conducted,” Benitez said.

Space-faring gardens

He suggested that introducing microbes that are beneficial to human health might be better than constantly struggling to wipe out all microbial life on the station. And while some modules up there do need to be sterilized, keeping some beneficial microbes alive could be achieved by designing future spacecraft in a way that accounts for how the microbes spread.

“We found that microbes in modules with little human activity tend to stay in those modules without spreading. When human activity is high in a module, then the microbes spread to adjacent modules,”  Zhao said. She said spacecraft could be designed to put modules with high human activity at one end and the modules with little to no human activity at the opposite end, so the busy modules don’t contaminate the ones that need to remain sterile. “We are of course talking as microbiologists and chemists—perhaps spacecraft engineers have more pressing reasons to put certain modules at certain spots,” Zhao said. “These are just preliminary ideas.”

But what about crewed deep space missions to Mars and other destinations in the Solar System? Should we carefully design the microbial composition beforehand, plant the microbes on the spacecraft and hope this artificial, closed ecosystem will work for years without any interventions from Earth?

“I’d take a more holistic ecosystem approach,” Benitez said. He imagines in the future we could build spacecraft and space stations hosting entire gardens with microbes that would interact with plants, pollinators, and animals to create balanced, self-sustaining ecosystems. “We’d not only need to think about sending the astronauts and the machines they need to function, but also about all other lifeforms we will need to send along with them,” Benitez said

Cell, 2025. DOI: 10.1016/j.cell.2025.01.039

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did-the-snowball-earth-give-complex-life-a-boost?

Did the snowball Earth give complex life a boost?

Biology, evolution, geology, glaciers, Science, snowball earth / /

Life is complex

But when new minerals made their way to the water, what did they actually do? Cycle throughout the bottom of the ocean, delivering new elements to previously barren locations and providing energy for microbial life. At the end of the Cryogenic, these early lifeforms appear to have gotten gradually more complex, paving the way for the first known multicellular life in the ensuing Ediacaran.

“Any time there’s a really radical environmental shift, we know that’s an interesting time for evolution,” says Chris Kempes, a theoretical biophysicist at the Sante Fe Institute who was not involved in the research. For example, when temperatures drop or less sunlight is available, organisms’ speed and metabolic rates generally slow down, creating new pressures on life, Kempes’ research has found. Halverson thinks the extreme habitats that life had to endure during the snowballs played more of a role in shaping evolution than the nutrient flushes from glaciers.

Even so, studies like Kirkland’s that try to understand how nutrients and energy availability changed throughout history are “the key to understanding when and why there are major evolutionary transitions,” Kempes says.

To determine what other minerals may have been key players in the ancient oceans, Kirkland hopes to look at rocks called apatites, which contain oxygen and other elements like strontium and phosphorus. However, these break down much easier than zircon-rich rocks, meaning they are less stable through long stretches of time.

Though the global changes of the Cryogenic happened eons ago, Kirkland sees parallels with the wide-scale climate changes of today. “The atmosphere, the land, and the oceans are all interconnected,” he says. “Understanding these [ancient] cycles gives us information about how more modern cycles on the planet may work.”

Geology, 2025.  DOI:  10.1130/G52887.1

Hannah Richter is a freelance science journalist and graduate of MIT’s Graduate Program in Science Writing. She primarily covers environmental science and astronomy. 

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flashy-exotic-birds-can-actually-glow-in-the-dark

Flashy exotic birds can actually glow in the dark

Biology, bioluminescence, birds, feathers, Fluorescence, Science / /

Found in the forests of Papua New Guinea, Indonesia, and Eastern Australia, birds of paradise are famous for flashy feathers and unusually shaped ornaments, which set the standard for haute couture among birds. Many use these feathers for flamboyant mating displays in which they shape-shift into otherworldly forms.

As if this didn’t attract enough attention, we’ve now learned that they also glow in the dark.

Biofluorescent organisms are everywhere, from mushrooms to fish to reptiles and amphibians, but few birds have been identified as having glowing feathers. This is why biologist Rene Martin of the University of Nebraska-Lincoln wanted to investigate. She and her team studied a treasure trove of specimens at the American Museum of Natural History, which have been collected since the 1800s, and found that 37 of the 45 known species of birds of paradise have feathers that fluoresce.

The glow factor of birds of paradise is apparently important for mating displays. Despite biofluorescence being especially prominent in males, attracting a mate might not be all it is useful for, as these birds might also use it to signal to each other in other ways and sometimes even for camouflage among the light and shadows.

“The current very limited number of studies reporting fluorescence in birds suggests this phenomenon has not been thoroughly investigated,” the researchers said in a study that was recently published in Royal Society Open Science.

Glow-up

How do they get that glow? Biofluorescence is a phenomenon that happens when shorter, high-energy wavelengths of light, meaning UV, violet, and blue, are absorbed by an organism. The energy then gets re-emitted at longer, lower-energy wavelengths—greens, yellows, oranges, and reds. The feathers of birds of paradise contain fluorophores, molecules that undergo biofluorescence. Specialized filters in the light-sensitive cells of their eyes make their visual system more sensitive to biofluorescence.

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