Health & Science

Mankind’s tangled family tree

A 400,000-year-old thighbone found in a Spanish cave has yielded the earliest DNA recovered from a human ancestor, and it suggests that our species’s family tree may include some surprises, reports The New York Times. The bone, found in an icy-cold cave in Spain amid a pile of other fossils, yielded a well-preserved sample of DNA from a time before Homo sapiens evolved. In that era, several human-like species lived in Africa, Europe, and Asia. Neanderthals are believed to have prevailed throughout Europe, while another human cousin called the Denisovans colonized Siberia. To the surprise of scientists, the DNA of the thighbone found in Spain was very similar to that of the Denisovans, who supposedly lived 4,000 miles away. One possible explanation is that Neanderthals and Denisovans interbred; another is that the two species had a common ancestor that has never been identified. Whatever the explanation, it appears that the species competing for survival 400,000 years ago were not as genetically distinct as anthropologists believed, and that modern humans have some genes from several species, including the Neanderthals and the Denisovans. “The story of human evolution is not as simple as we would have liked to think,” said study author Matthias Meyer, a molecular biologist at the Max Planck Institute for Evolutionary Anthropology in Germany. “The likelihood of interbreeding is quite high.”

How gender influences brains

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Men and women really are wired differently. A new gender-based study that involved mapping brains found a striking contrast in neural circuitry that its authors are calling the “hunter vs. gatherer divide.” The brain-circuit maps “provide a potential neural basis as to why men excel at certain tasks, and women at others,” says Ragini Verma, an associate professor at the Perelman School of Medicine, tells the Los Angeles Times. Researchers looked at the brains of about 950 young people, using an MRI technique. The result was a map of each person’s connectome, or brain network, highlighting the fiber pathways that link different regions. In general, male brains were found to have more connections from front to back within one hemisphere, which makes them optimized for coordinating perception with action, such as learning a new sport or following directions to a location. Female brains generally have more connections between the left and right hemispheres, which enables them to integrate emotion, reason, and social cues in responding to situations. But Verma said these gender differences are not hard and fast, varying from individual to individual, and that it is unclear how much social conditioning combined with hormonal differences to shape neural connections. “Every individual could have part of both men and women in them,” she said.

Hot to make a purchase

If you step into a well-heated store this holiday season, it’s probably not because the thermostat is faulty. Israeli researchers have demonstrated that people are willing to pay more for products when they feel comfortably warm—what they call the “temperature-premium effect,” reports Pacific Standard. Researchers confirmed the phenomenon in several studies, including one that primed 46 college students by having them hold a warm or cool therapeutic pad for 10 seconds; they then were asked to name the maximum price they would pay for a slice of chocolate cake and a six pack of batteries. Participants who’d held the warm pad were willing to pay significantly more for both. In another study, 109 students were put into rooms at temperatures either four degrees higher or lower than 72 Fahrenheit and asked how much they would pay for 11 different products typically purchased by college students. The warm-roomers were willing to pay more for nine of the 11 products. “Physical warmth induces emotional warmth, which generates greater positive reactions,” says study author Yonat Zwebner of Hebrew University.

The alcoholism gene

The drinking habits of laboratory mice have led scientists to identify a gene mutation that creates a predisposition for alcohol addiction, ScienceDaily.com reports. Researchers found that mice with a mutated Gabrb 1 gene overwhelmingly preferred drinking alcohol to water, choosing to consume almost 85 percent of their daily fluid as alcohol about the strength of wine. They’d even work to get alcohol by pushing a lever. By contrast, normal mice showed no interest in alcohol. Researchers say the mutation creates spontaneous electrical activity in the pleasure zone of the brain that creates a craving for pleasurable experiences, including intoxication. Study author Quentin Anstee of Newcastle University says it’s unlikely that a single mutation causes alcoholism in people. “It’s more like a whisper in the ear that is present that makes certain life choices seem more pleasurable or easier,” he said.