For those of us whose memory of high school biology hasn't faded entirely, planarians will probably sound very familiar. They're generally used as an example of one of the extreme ends of regenerative capacity. While some animals like mammals have a limited ability to regenerate lost tissues, planarians can be cut roughly in half and regenerate either an entire head or entire tail, depending on which part of the body you choose to keep track of.

In doing so, they have to re-establish something that is typically only needed early in an animal's development: a signaling system that helps tell cells where the animal's head and tail are. Now, a US-based team asked a question that I'd never have thought of: What happens if you cut the animal in half early in development, while the developmental head-to-tail signaling system is still active? The answer turned out to be surprisingly complex.

Heads or tails?

Planarians are small flatworms that would probably be living quiet lives somewhere if biologists hadn't discovered their ability to regenerate lots of adult tissues when damaged. The process has been well-studied by this point and involves the formation of a cluster of stem cells, called a blastema, at the site of damage. From there, many of the signals that control the formation of specialized tissues in the embryo get re-activated, directing the stem cells down the developmental pathways needed to reproduce any lost organs.

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In a Black Mirror -esque turn, some cash-strapped actors who didn't fully understand the consequences are regretting selling their likenesses to be used in AI videos that they consider embarrassing, damaging, or harmful, AFP reported .

Among them is a 29-year-old New York-based actor, Adam Coy, who licensed rights to his face and voice to a company called MCM for one year for $1,000 without thinking, "am I crossing a line by doing this?" His partner's mother later found videos where he appeared as a doomsayer predicting disasters, he told the AFP.

South Korean actor Simon Lee's AI likeness was similarly used to spook naïve Internet users but in a potentially more harmful way. He told the AFP that he was "stunned" to find his AI avatar promoting "questionable health cures on TikTok and Instagram," feeling ashamed to have his face linked to obvious scams.

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After obliterating the federal office on long COVID and clawing back billions in COVID funding from state health departments, the Trump administration has now entirely erased the online hub for federal COVID-19 resources. In its place now stands a site promoting the unproven idea that the pandemic virus SARS-CoV-2 was generated in and leaked from a lab in China, sparking the global health crisis.

Navigating to COVID.gov brings up a slick site with rich content that lays out arguments and allegations supporting a lab-based origin of the pandemic and subsequent cover-up by US health officials and Democrats.

Previously, the site provided unembellished quick references to COVID-19 resources, including links to information on vaccines, testing, treatments, and long COVID. It also provided a link to resources for addressing COVID-19 vaccine misconceptions and confronting misinformation . That all appears to be gone now, though some of the same information still remains on a separate COVID-19 page hosted by the Centers for Disease Control and Prevention .

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Mars has not always been a seemingly lifeless red desert. We have evidence that billions of years ago it had a warm, habitable climate with liquid water in lakes and flowing rivers , which is somewhat confusing, given that Mars is much farther from the Sun than the Earth and that the Sun was much less bright back then. “In order for Mars to be warm enough to host liquid water, there must have been a lot of carbon dioxide in the atmosphere,” says Benjamin Tutolo, a researcher at the University of Calgary. “The question we’ve been asking for at least 30 years was where the record of all this carbon is.”

Tutolo led a new study of rock samples collected by the Curiosity rover that might have answered this question.

The tallest sediment stack

The mystery of Mars’ missing carbon stems from two seemingly conflicting results. On the one hand, we have already found dried riverbeds and lakes on the surface of Mars, so we know there must have been liquid water on its surface at some point. To account for the presence of this water, every Martian climate model we have run indicates that huge amounts of atmospheric carbon were needed to provide a sufficient greenhouse effect to keep the surface temperature above freezing. But the data we were getting from satellite observations of Mars found much less carbon in the Martian soil than those climate models would suggest. “So, either the models were incorrect—and there’s no good reason to believe that—or there really was lots of carbon in the Martian atmosphere,” Tutolo says.

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There are so many factors that can influence how we perceive others, which in turn can determine the people we choose as platonic friends or romantic mates. We certainly make snap judgments based on physical appearance, but scent can have a powerful influence, too. According to a new paper published in the journal Scientific Reports, two heterosexual women meeting for the first time rely partly on scent to judge whether they want to be friends with each other, deciding within minutes—practically at first whiff—whether there is friendship potential.

Social olfactory research largely stems from evolutionary psychology, specifically the work of Swiss biologist Claus Wedekind in 1995. Subtle chemical signals from pheromones are known to play a role in attraction in many species. Scientists had already found evidence in fish and mice that the major histocompatibility complex (MHC) genes, which are critical for immune system function (and useful in determining tissue compatibility for transplants, for instance)—showed a marked preference for sexual partners with different MHC genes, perhaps as a way of keeping the gene pool well-mixed and protecting against inbreeding.

Wedekind introduced the so-called "sweaty T-shirt" method to study the possible role of MHC in mate preferences in humans. Male participants wore the same T-shirt for two days, which were then placed in identical boxes. Women participants then smelled each shirt and indicated which ones they found most sexually attractive. Wedekind found that the women overwhelmingly preferred the T-shirt smells of men who had the most dissimilar MHCs to their own. The only caveat: The preference was reversed in women who were taking oral birth control.

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Popular online shopping meccas Temu and Shein have finally broken their silence, warning of potential price hikes starting next week due to Donald Trump's tariffs.

Temu is a China-based e-commerce platform that has grown as popular as Amazon for global shoppers making cross-border purchases, according to 2024 Statista data . Its tagline, "Shop like a billionaire," is inextricably linked to the affordability of items on its platform. And although Shein—which vows to make global fashion "accessible to all" by selling inexpensive stylish clothing—moved its headquarters from China to Singapore in 2022, most of its products are still controversially manufactured in China, the BBC reported .

For weeks, the US-China trade war has seen both sides spiking tariffs. In the US, the White House last night crunched the numbers and confirmed that China now faces tariffs of up to 245 percent, The Wall Street Journal reported . That figure includes new tariffs Trump has imposed, taxing all Chinese goods by 145 percent, as well as prior 100 percent tariffs lobbed by the Biden administration that are still in effect on EVs and Chinese syringes.

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Cupra provided flights from Washington to Miami and accommodation so Ars could drive its cars and attend the Miami ePrix. Ars does not accept paid editorial content.

MIAMI—The arrival of a new car brand to the US was always going to pique my interest, even before the current government decided to upend the automotive sector with punitive tariffs. So when Cupra invited me to come check out some of its cars and hear about its plan to launch here in America, I wanted to know more. My burning question was probably the same one you have as you read this: "Isn’t this a terrible time to try to launch a new car brand in the US?"

What’s a Cupra?

One of the brands of the sprawling Volkswagen Group, you can think of Cupra as sort of a Spanish Polestar. Originally, it was a high-performance badge given to some Seats (Seat being VW's budget brand from Spain), which then got spun out into a standalone brand.

OK, it's not a perfect analogy: Cupra is not a luxury brand, nor is it just electric vehicles. But it was created to fill a gap between the mass market and premium brands, with a focus on design and performance to attract a younger customer than VW's existing brands. "We are not a brand for everyone," said Chief Brand Officer Igansi Prieto.

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Nintendo announced Friday morning that a number of accessories for the Switch 2 "will experience price adjustments from those announced on April 2 due to changes in market conditions." And while the launch price of the console hardware and Nintendo's first-party exclusive games is not changing for now, the company warned that "other adjustments to the price of any Nintendo product are also possible in the future depending on market conditions."

The announcement comes as Nintendo has set a new date of April 24 to open US preorders for the Switch 2. Those preorders were initially delayed from a planned April 9 opening so Nintendo could "assess the potential impact of tariffs and evolving market conditions" on the console's launch. "We apologize for the retail pre-order delay, and hope this reduces some of the uncertainty our customers may be experiencing," Nintendo said in its announcement Friday.

Here are the newly announced planned prices for Nintendo's official Switch 2 accessories (the original prices announced on April 2 are struck out in parentheses):

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The creators of Sunderfolk wanted to make a video game that would help players “Rediscover game night.” By my reckoning, they have succeeded, because I am now regularly arguing with good friends over stupid moves. Why didn’t I pick up that gold? Don’t you see how ending up there messed up an area attack? Ah, well.

That kind of friendly friction, inside dedicated social time, only gets harder to come by as you get older, settle into routines, and sometimes move apart. I’ve hosted four Sunderfolk sessions with three friends, all in different states, and it has felt like reclaiming something I lost. Sunderfolk is a fun game with a lot of good ideas, and the best one is convincing humans to join up in pondering hex tiles, turn order, and what to name the ogres who shoot arrows (“Pointy Bros”).

Maybe you already have all the gaming appointments you need with friends, online or in person. Sunderfolk , I might suggest, is a worthy addition to your queue as a low-effort way to give everyone a break from being the organizer. It does a decent job of tutorializing and onboarding less experienced players, then adds depth as it goes on. Given that only one person out of four has to own the game on some system, and the only other hardware needed is a phone, it’s a pretty light lift for what I’m finding to be a great payoff. Some parts could be improved, but the core loop and its camaraderie engine feel sturdy.

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