Nope, males aren’t larger than females in most mammal species

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Hello Nature readers, Today we learn about the myth of bigger male mammals, explore what OpenAI's Sora text-to-video AI tool might mean for science and consider the way we think about menopause.

The most dimorphic species was the northern elephant seal (Mirounga angustirostris), where males had a mean mass 3.2 times that of females (Michele and Tom Grimm/Alamy)

Most male mammals aren't larger An analysis of more than 400 mammal species is overturning Charles Darwin's assertion that in most, males are larger than females. In fact, this is only the case for 45% of species, with 39% showing no sexual size dimorphism and 16% having larger females than males. "There's been this really strong inertia toward the larger male narrative, but it was just based on Darwin's hand-wavy statement, and the evidence doesn't really support it," says evolutionary biologist and study co-author Kaia Tombak. Scientific American | 4 min read Reference: Nature Communications paper

Biden seeks science funding boost US President Joe Biden has proposed modest increases in federal spending on science and innovation for the 2025 fiscal year, including a 20% increase for the Environmental Protection Agency and more than 5% for the Centers for Disease Control and Prevention. Similar proposals in previous years have run up against opposition among lawmakers in Congress, who decide how much the government will spend. Biden's budget "is nothing more than a showcase for the policies and the spending that the White House would like to pursue if it had the ability to do so, which it doesn't," says Michael Lubell, a physicist who tracks science-policy issues. Meanwhile, negotiations continue over the 2024 budget: much of the federal government — including the National Institutes of Health, the world's largest public funder of biomedical research — is poised to shut down in less than two weeks unless lawmakers act. Nature | 8 min read

How text-to-video AI could change science The release of OpenAI's Sora text-to-video AI tool last month was met with a mix of excitement and trepidation from researchers who are concerned about misuse of the technology. Some say the result will be a deluge of fake but compelling video and audio, which poses particular problems for upcoming elections. But such tools could be used for good too, such as communicating findings to a lay audience and enabling researchers to wade through huge datasets. Nature | 4 min read

This footage isn't real — it was created by the AI tool Sora. The system seems to be able to produce more photorealistic and compelling content from simple text prompts than other video-generating algorithms. (OpenAI)

Features & opinion

What WebAssembly can do for you WebAssembly can compile code written in dozens of programming languages, including C, C++ or Rust, and works inside a browser — no installation required. Researchers are using it to build analysis tools for scientific data, which can then be run even on low-power laptops or phones. But users must brace themselves for complications. "You often have to modify the original code to get around things that WebAssembly doesn't support," says bioinformatics software engineer Robert Aboukhalil. Check out a demo from Nature technology editor Jeffrey Perkel. Nature | 8 min read

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How to fix broken PhD assessment Most PhDs are assessed on their final dissertation — something that hasn't changed for at least half a century. Reform is urgently needed, argues a Nature editorial. Part of the problem is that few doctoral supervisors have teaching qualifications or awareness of education innovations. "At a minimum, doctoral supervisors should take the time to engage with the research that exists in the field of PhD education, and how it can apply to their interactions with students." Nature | 5 min read

Has the menopause become over-medicalized? Last week, The Lancet published a conversation-sparking editorial arguing that "commercial companies and individuals with vested interests have over-medicalized menopause". The oversimplified idea of menopause as a health problem to be solved by hormone replacement therapy (HRT) is not based on evidence, argued a series of papers and perspectives in the journal. "Menopause does not herald the start of a period of decay and decline but is a developmental life stage," says the editorial. In UnHerd, physician Margaret McCartney and health journalist Deborah Cohen dig into the evidence for the benefits of HRT and the therapy's cultural and historical context. "There was a time when women were expected to shut up and put up" with symptoms such as hot flashes, they write. Now, in some ways, the pendulum has swung too far in the other direction, says public health researcher Brooke Nickel, who studies the language used to sell HRT products to women. "They're really spinning that feminist narrative around," she says. "If you don't do something, you're not taking control of your body or you're being oppressed by other people." The Lancet editorial | 5 min read, part of its series on menopause & UnHerd | 10 min read

Image of the week

These adornments made from the teeth of animals including bear (1), elk (4) and fox (6,7) were crafted by Gravettian hunter-gatherers — the culture responsible for the iconic Venus of Willendorf figurine. Researchers analysed thousands of such personal ornaments, along with genetic data. They found that the variety in the jewellery styles couldn't be fully explained by how far apart groups lived, and identified nine distinct cultural groups existing in Europe between 34,000 and 24,000 years ago. These groups mostly align with genetic data, but also reveal more nuanced patterns, indicating that culture and genetics are interconnected but not perfectly aligned. (Nature Human Behaviour | 43 min read) (Jack Baker et al/Nature Human Behaviour)

Quote of the day "As environmental, social and humanitarian crises escalate, the world can no longer afford two things: first, the costs of economic inequality; and second, the rich." The science is clear, argue epidemiologists Richard Wilkinson and Kate Pickett: places with large gaps between rich and poor tend to have worse health statistics, more violence and worse pollution than do more-equal countries. (Nature | 9 min read)

I'm paralyzed with jealousy that I won't be witnessing the total solar eclipse visible in parts of the United States, Canada and Mexico on 8 April. But I can still enjoy the fact that researchers will be observing how animals react to the unusual experience. During a 2017 eclipse that passed over a South Carolina zoo, "to our astonishment, most of the animals did surprising things," says biologist Adam Hartstone-Rose. I hope you'll eclipse my inbox with your feedback on this newsletter. Your e-mails are always welcome at briefing@nature.com. Thanks for reading, Flora Graham, senior editor, Nature Briefing With contributions by Gemma Conroy, Katrina Krämer and Smriti Mallapaty

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