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Top stories: simulating galaxies, Great Barrier die-offs, and combating sexual harassment

Galaxy simulations are at last matching reality—and producing surprising insights into cosmic evolution

For decades, scientists have tried to simulate how the trillions of galaxies in the observable universe arose from clouds of gas after the big bang. But in the past few years, thanks to faster computers and better algorithms, the simulations have begun to produce results that accurately capture both the details of individual galaxies and their overall distribution of masses and shapes. “In the past the simulations were always trying to keep up with the observations,” says Stephen Wilkins, an extragalactic astronomer at the University of Sussex in Brighton, U.K. “Now we can predict things that we haven't observed.”

The Great Barrier Reef has had five near-death experiences in the past 30,000 years

Thirteen thousand years ago, as the last ice age ended, entire stretches of Australia’s Great Barrier Reef perished. Rising sea levels blanketed the world’s largest collection of corals with sediment coming off the newly inundated land, blocking the sunlight corals need to grow. The reef eventually recovered, but it took hundreds to thousands of years. This near death and eventual resurrection wasn’t a one-off, according to a new study that reveals the reef’s shifting boundaries over geological time. It’s a tale that has played out five times over the past 30,000 years—and it may be happening again today.

Will U.S. academies expel sexual harassers?

As high-profile sexual harassment cases fuel public criticism, the presidents of the U.S. National Academies of Sciences, Engineering, and Medicine announced last week they may adopt new policies allowing the prestigious bodies to eject members who have committed harassment and other forms of misconduct. Members of the academies—which serve as both honorific societies and advisers to the U.S. government—are elected by existing members to life-long terms, and the bodies currently lack mechanisms for removing them for harassment.

Iceland’s founding fathers underwent a rapid, 1000-year genetic shift

If modern Icelanders came face-to-face with their founding fathers, they’d be hard-pressed to see much family resemblance, according to a new study. That’s because today’s Icelanders have a much higher proportion of Scandinavian genes than their distant ancestors did, suggesting the islanders underwent a remarkably rapid genetic shift over the past thousand years.

This ancient fish was bigger than a whale shark—and faster than scientists ever imagined

Scientists have long struggled to explain why bony fishes are so small: The heaviest—the ocean sunfish—is just 2.3 metric tons, but cartilaginous fishes like whale sharks can weigh up to 34 metric tons. Now, a new study of an ancient fish, which grew to at least 16.5 meters in length and might have weighed 45 metric tons, suggests this modern difference is merely an evolutionary accident.