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Top story:  “Dolphin moms speak ‘baby talk’ like we do.”

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27th June, 2023
Today’s Protostar is Fangfang Yao, whose research uncovered startling declines in global lake water storage over the last three decades. But first, catch up on the latest science news, including newly discovered evidence that hominins butchered one another and a potential new ally in the fight against antibiotic resistance.
Dolphin moms speak ‘baby talk’ like we do
Scientists have dubbed the sing-songy way that parents talk to babies “motherese.” Studies suggest this special baby talk helps infants bond with caregivers and learn the complexities of language. Now, scientists suspect we aren’t the only species with a special way of speaking to our youngest: Bottlenose dolphins (Tursiops truncatus) also raise the pitch of their voice when talking to their calves, according to a study published yesterday in PNAS.

Researchers made the discovery by analyzing the whistles of female dolphins in Florida that were undergoing health assessments for ongoing research. The whistles mother dolphins produced around their babies reached higher pitches and exhibited a greater range of frequencies than ones they made when alone or around other dolphins, the team found—shifts similar to the ones human voices make when speaking motherese.

The team suspects that, like with our baby talk, dolphin motherese may help grab the young one’s attention. The work may provide insight into the evolution of vocal learning, a prerequisite for language, says Janet Mann, a behavioral ecologist and bottlenose dolphin expert at Georgetown.

Meat is meat: Evidence for butchering of hominins
Hominin bone with zoom in on region showing vertical marks on bone
A zoom of this hominin tibia reveals what researchers believe are cuts from stone tools (vertical marks). JENNIFER CLARK
The shape and patterns of marks on ancient bones can tell stories of how animals died. For instance, marks on 3.4-million-year-old antelope bones indicate that human ancestors carved up their carcasses long ago. Now, a team has found similar grooves on a 1.45-million-year-old hominin tibia, suggesting that our closest relatives butchered one another.

The discovery occurred somewhat by accident when researchers were examining bones in the collection of the Nairobi National Museum to discover what predators plagued our ancient relatives. When the team looked up close, they found evidence that one particular leg had been bitten by a big cat, but also bore the kind of parallel marks made by stone butchering tools. Because the hominin- and feline-made grooves don’t overlap, it’s impossible to tell who got to the leg first. It’s also not certain that any meat cut from the bone by human ancestors was consumed, but the team says that’s the most likely scenario. However, not all experts that spoke with  Science News agreed with that interpretation.

Though not the first hint that hominins made meals of one another, the bone is “a really interesting and amazing discovery,” University of Brighton archaeologist James Cole tells The Washington Post. And it was just sitting there, waiting for someone to notice it—a reminder of just how valuable museum collections are.

A potential vaccination strategy for diarrheal disease
According to the World Health Organization, diarrheal disease is the leading cause of child mortality and morbidity globally. Caused by certain strains of bacteria, the disease kills more than 500,000 kids under the age of five every year, and no vaccine exists. Yet, sometimes, people are infected and show no symptoms at all. By trying to understand why that is, researchers may have uncovered a way to turn disease-causing bacteria into a vaccine against future infections and severe symptoms.

The team was examining how diet affects disease severity when they discovered that mice fed a high-iron diet survived what should have been lethal diarrheal infections. Not only that, these animals were basically symptom-free. That’s because the excess iron slowed the absorption of sugar, essentially flooding their intestines with a feast for the microbes. Fat and happy, these bacteria didn’t attack the intestinal walls. When the mice were switched back to a regular diet, their lack of symptoms persisted. And when they were reinfected a month later, they again had a mild infection—an indication that the initial infection had induced lasting immunity.

The researchers are careful to note that this mouse work is very preliminary and more research is needed to establish whether iron similarly helps people. Either way, the findings point to a potential new strategy for developing vaccines against this pernicious disease: pairing a specific diet with a bacterial culprit.

Evolution blockers: A way to prevent antibiotic resistance?
The advent of antibiotics completely changed medicine and saved countless lives. Unfortunately, as their use became widespread, the bacteria they annihilated started to evolve. The discovery of new antibiotics has failed to keep pace with growing multidrug resistance, moving humanity closer to what some are calling a “postantibiotic era.”

One way to avoid that dystopian prediction could be to keep bacteria from mutating, thus preventing them from evolving resistance in the first place. Now, researchers may have found a drug that does just that. By screening more than one thousand already-approved pharmaceuticals, they discovered one that keeps Escherichia coli from evolving resistance to the antibiotic ciprofloxacin in culture and in experimental animals. The drug, called dequalinium chloride, prevents the  starvation response induced in the bacteria by the antibiotic, and in doing so, keeps the microbe from generating DNA breaks that facilitate mutations conferring resistance, they report in Science Advances.

The idea would be to administer such drugs alongside antibiotics to prevent infections from developing resistance. Whether that’s clinically feasible or useful remains to be seen. Still, the findings provide hope that this kind of one-two punch strategy could prolong the lifespan of our current antibiotics, buying time to find new ones.

Fangfang Yao beside the Great Salt Lake in Utah
Fangfang Yao beside the Great Salt Lake in Utah. COURTESY OF FANGFANG YAO
Fangfang Yao
Postdoctoral fellow, Environmental Resilience Institute, University of Virginia

Yao, F et al. Satellites reveal widespread decline in global lake water storage. Science 380, 743–749 (2023). 10.1126/science.abo2812

Fangfang Yao credits his interest in hydrology to growing up in a city along the Yangtze River in China. “I would watch the rise and fall of the river,” he explains, so when it came time to pick a field of study, he was drawn towards working on water-related environmental issues.

Given that lakes store almost 90% of the Earth’s liquid surface fresh water, Yao decided to focus his postdoctoral research at the University of Colorado, Boulder on uncovering global trends in lake water storage. Using a remarkable dataset covering nearly 30 years, he and his colleagues determined gains and losses in lake water for 1972 of the world’s largest lakes, which combined account for 96% of natural lake waters and 83% of humanmade reservoir waters.

Their findings, published in May in Science, made a big splash, so ScienceAdviser reached out to Yao to chat about the work and its implications. Our conversation has been edited for brevity.

What were your big findings?
There are three major findings. The first one is quite surprising: More than half of the Earth’s largest water bodies were drying over the past three decades.

Secondly, we [link this drying] to human overconsumption—a direct human impact—and to indirect human impacts through climate change. So, human factors were largely responsible for the decline in liquid storage.

Third—another surprising finding to us—we find nearly one-quarter of the human population resides in basins with a large drying lake, underscoring the potential importance of management solutions.

What should happen now that we know that these lakes are drying?
I believe the most direct impact of this study is to raise awareness. Awareness is really the key to doing any conservation and management.

[In addition to the paper], we provided a global database to allow people to see, in a map, which lakes are drying globally. And we’ve also identified, for natural lakes, what is the primary driver for the observed water loss. So, they can incorporate those into water management.

Also, we established the overlooked impact of sedimentation on reservoirs. The sediment load from rivers is getting trapped in reservoirs and gradually filling them up. We need to be aware of these kinds of issues, particularly if you consider the possible impacts of climate change: wildfires loosen soils and trigger more landslides; more extreme precipitation. These, of course, accelerate the sedimentation rates in some reservoirs.

Lakes are pretty much standalone water resources, which leaves their management to local entities. This is unlike river basins, which are often managed at a large scale. [Because of this], some people may argue that, in terms of management, lakes are the stepchild of rivers, receiving less attention. So with our findings, we really want to see more integrated management of lakes. And not only the water quantity but the water quality.

So these are all the kinds of things that we really want to see through increasing awareness … to save these water bodies and maintain the socioeconomic functions of these lakes into the future.

What’s next for you?
My peers in this field and I are really excited about the new opportunities from recent satellite missions, such as the Surface Water and Ocean Topography mission or SWOT that was launched by NASA last December. For land hydrology, it will provide unprecedented measurements for lake water storage for all lakes larger than one hectare. Our study focused on lakes that are large and extra wide because of the capacity of satellite observations at that time. But now, we can use SWOT observations to really extend the work to a number of smaller water bodies that might be more locally important.

There are also important questions that have not been well-addressed in the field of hydrology. One in particular is the interactions between surface water and groundwater. For example, how drying lakes are contributing to groundwater declines and the decreasing water table in some regions, and the reverse: how groundwater pumping in some heavily irrigated areas contributes to the observed lake water storage declines. So there are interesting questions that need to be answered, and I’m really excited about the opportunities to tackle these new questions.

Natural green
Environmental degradation is extremely costly to global GDP—to the tune of $75 billion a year, finds a new study. But enacting nature-friendly policies could flip that to hundreds of billions in gains.
A stellar ending
A powerful gamma ray burst led astronomers to discover a new kind of star death. Instead of going supernova, two stars collided—an event unlikely to happen in our galaxy because there’s just too much wiggle room.
Drug resistance: Plastics make it possible
Marine microbes exposed to chemicals leeched from microplastics end up with more virulence and antibiotic resistance genes than those not exposed. Though the mechanism isn’t fully known, researchers suspect the uptick could come from a general selective pressure to be flexible in the face of the toxic compounds.
Ultimately, we express our humanity through art, so understanding and shaping the impact of AI on creative expression is at the center of broader questions about its impact on society.
Last but not least
Did you know that cities around the world are getting colorful new inhabitants? That reminds me—I should make sure to go birding in Seward Park the next time I’m in Seattle.
Christie Wilcox, editor, ScienceAdviser
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