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Even before a game begins, an athlete’s body changes: heart rate increases, hormones surge and beads of sweat dapple the skin. Competition is such a visceral experience that the mere anticipation of a challenge excites our instincts to fight. These biological responses are even more pronounced when people face an opponent they have come to know and despise, an opponent they must battle again and again—a rival. In a 2003 study psychologists at Northumbria University in England found much higher testosterone levels in soccer players preparing to play against a team they considered an extreme rival than in those matched up with a moderate rival....

By Katharine Sanderson of Nature magazineThe most direct evidence yet for ancient photosynthesis has been uncovered in a fossil of a matted carpet of microbes that lived on a beach 3.3 billion years ago.Frances Westall at the Centre for Molecular Biophysics, a laboratory of the French National Centre for Scientific Research (CNRS), in Orleans and her colleagues looked at the well-preserved Josefsdal Chert microbial mat–a thin sheet formed by layer upon layer of tiny organisms–from the Barberton Greenstone Belt in South Africa....

Humans have been riding rockets into space for more than 50 years, and for all that time, the cost of reaching orbit has remained astronomical—$5,000 to $50,000 per kilogram, depending on which rocket is used. The problem is that none of our rockets is very efficient. About 90 percent of a rocket’s weight is fuel and propellant, leaving little room for payload. If it could lose some of that weight, a rocket could lift more cargo, reducing the cost of putting a given kilogram of stuff into orbit....

The recipe for mammalian life is simple: take an egg, add sperm and wait. But two new papers demonstrate that there’s another way. Under the right conditions, stem cells can divide and self-organize into an embryo on their own. In studies published in Cell and Nature this month, two groups report that they have grown synthetic mouse embryos for longer than ever before. The embryos grew for 8.5 days, long enough for them to develop distinct organs — a beating heart, a gut tube and even neural folds....

By Laura Zuckerman SALMON, Idaho (Reuters) - The Nez Perce tribe once hunted bison in what is now Yellowstone National Park, and some tribal leaders want to revive the practice, which ended with Western settlement and the near total extermination of the once-vast U.S. bison herds. Today, remnants of the bison, or buffalo, herds still roam the grasslands and river valleys of Yellowstone, a huge park that covers parts of Wyoming, Montana and Idaho....

For decades the cell nucleus has been a black box of biology—scientists have understood little about its structure or the way it operates. But thanks in part to new visualization technologies, biologists have recently begun probing the architecture of the nucleus in real time. And they are discovering that this architecture appears to change as we age or fall ill or as our needs shift. In fact, the structure of nuclear components—chromosomes, RNA, protein complexes and other small bodies—could be as biologically important as the components themselves....

Diagnosing Alzheimer’s disease is difficult—confirmation can be obtained only postmortem, by verifying at autopsy that the brain has an abundant amount of plaque made up of the sticky beta-amyloid protein. To gauge Alzheimer’s in living patients, neurologists must depend on time-consuming assessments of the brain’s degeneration—such as monitoring progressive memory loss—that often delay a conclusive judgment. Now a new technique is poised to greatly speed diagnosis. Ongoing studies at Uppsala University in Sweden have shown that the chemical agent dubbed Pittsburgh Compound-B, or PIB, is a highly accurate marker of plaque buildup and that its abundance in the brain can predict whether patients with mild cognitive impairment will develop Alzheimer’s—and when that decline will likely start....

Blackett’s War: The Men Who Defeated the Nazi U-Boats and Brought Science to the Art of Warfare by Stephen Budiansky Knopf, 2013 ($27.95) During World War II a relatively unheralded group of civilian researchers, led by British ex-naval officer and future Nobel Prize–winning physicist Patrick Blackett, collaborated on finding ways to subdue the Nazi U-boat fleet. Journalist Budiansky details how Blackett and his colleagues’ unconventional application of science and mathematics changed military strategy—for example, by applying probability theory to help determine the location of submarines....

Editor’s note: This story will appear in our January issue but is being posted early because of a publication in today’s Nature. Thousands of years after the last woolly mammoth lumbered across the tundra, scientists have sequenced a whopping 50 percent of the beast’s nuclear genome, they report in a new study. Earlier attempts to sequence the DNA of these icons of the Ice Age produced only tiny quantities of code....

By Barbara GoldbergNEW YORK (Reuters) - A fast-moving snowstorm barreled through the U.S. mid-Atlantic on Tuesday, cancelling flights, snarling roadways and shutting schools and government offices while winds kept the midsection of the country in an icy grip that killed at least 11 people.The East Coast’s first significant snowfall of the season dumped as much as 6 inches on northern Virginia, Maryland, Pennsylvania, Delaware and southern New England, according to the National Weather Service....

Advances in science and technology over the past century have made us more self-reliant and less vulnerable to mishaps such as natural disasters or disease outbreaks. As a result, members of the middle class today are much better off in many ways than the wealthiest individuals were a century ago. I realized this fact on a guided tour through the Gilded Age mansions of Newport, R.I., where I noticed that at the turn of the 20th century, the owners of these huge houses slept on narrow beds and learned that they lived a lifestyle marked by strict social rules, limited control over life-threatening risks, and what would now be considered rudimentary medical care....

If you’d heard only that a scientist who served in the Trump administration and now regularly appears on Fox News and other conservative media thinks climate change is a hoax, you’d roll your eyes and move on. But if you heard that someone associated with former President Barack Obama’s Democratic administration was calling the climate science consensus a conspiracy, the novelty of the messenger might make you take it a little more seriously....

Researchers have for the first time found that the neurotransmitter dopamine is central to the human brain network governing motivation and a sense of reward and pleasure—and that it changes with age. The finding could provide clues to healthy, happy aging and pave the way to new treatments for neurological disorders, including Parkinson’s disease and schizophrenia as well as addictive behaviors from alcoholism and drug abuse to compulsive gambling. The U....

RECIFE, BRAZIL — Baby Duda sat in bed, a pink barrette in her hair. She was ready to go home after a month in the hospital — when she began gasping for breath. Nurses rushed to her side with emergency oxygen. Her sister, out in the hallway, pressed her face against the window, watching yet another medical setback punctuated by high-pitched wails. Born last November with a head just 10 inches in circumference, Duda is one of Brazil’s Zika babies....

U.S. President Donald Trump’s administration approved TransCanada Corp’s Keystone XL pipeline on Friday, cheering the oil industry and angering environmentalists who had sought for years to block it. The approval reverses a decision by former President Barack Obama to reject the project, but fresh obstacles loom: To get built, TransCanada will need to win financing, acquire local permits, and fend off likely legal challenges. “It’s not done yet,” said Michael Wojciechowski, vice president of Americas, oil and refining markets research at consultancy Wood Mackenzie....

Yesterday was Earth Day, and we invited everyone to send us photos and videos of how they were celebrating the 45th annual event—or pitching in to improve our habitat. We heard about an interesting range of activities but one small boy may have epitomized the spirit and hands-on nature of the day best. Take a look at the 36-second video below. In it, “Khalid” is asked what he is doing, poking a stick at a plastic bag along the edge of a lake in Rochester, N....

In a colorfully decorated classroom, a five-year-old boy is asked to describe his favorite belonging. He talks effusively about the dinosaur T-shirt his mom forced him to put in the wash that morning. Then he plays two simple computer games, trying, of course, to win. But the fix is in: experimenters have arranged that he will win one game and lose the other (and, to avoid suffering harm, will win a third and final game at the experiment’s end)....

After hurricane Katrina devastated New Orleans in 2005, Keith Winfrey, a physician with a degree in public health, prayed to be sent to where he was needed. The answer was New Orleans. There, he opened New Orleans East Louisiana Community Health Center to give the eastern parishes the same kind of care that other areas receive. Since then, Winfrey — winner of the 2019 Catalyst for Change Award — and his team have increased colorectal screening rates from 3% to 80% in just six years, giving an underserved community valuable early detection for a treatable cancer....

Antioxidants are supposed to keep your cells healthy. That is why millions of people gobble supplements like vitamin E and beta-carotene each year. Today, however, a new study adds to a growing body of research suggesting these supplements actually have a harmful effect in one serious disease: cancer. The work, conducted in mice, shows that antioxidants can change cells in ways that fuel the spread of malignant melanoma—the most serious skin cancer—to different parts of the body....

Often called the “father of modern neuroscience,” Santiago Ramón y Cajal was a Spanish scientist whose exquisitely detailed drawings helped to reveal the pathways, cells and structure of the brain. Born in 1852, Cajal crafted illustrations, based on painstaking observations of brain slices under the microscope, that led to major discoveries long before neuroimaging was possible. He realized, for instance, that the brain was a vast network of individual neurons—a finding that led him to earn a Nobel Prize in 1906....