Health & Science

Between apes and humans; Life without oxygen; Calling all polliwogs; A diet to remember; The Japanese advantage 

Between apes and humans

Add yet another branch to the human evolutionary tree. Scientists working in South Africa have unearthed four well-preserved skeletons, including those of a mother and her son, that date back nearly 2 million years, to a time when hominids were evolving from Australopithecus, an ape-like genus, to the more modern genus Homo. Dubbed Australopithecus sediba, the skeletons exhibit “a fascinating mosaic of features,” Smithsonian paleontologist Rick Potts, who was not part of the research team, tells The New York Times. The creatures—which apparently fell into a sinkhole and drowned—had modern legs and hips for walking upright, but long arms for climbing trees; the face and small teeth of Homo, but with small feet and a brain only about a third the size of those of humans. The hominids may be direct ancestors of humans or “a very close side branch mimicking the earliest members of Homo,” lead researcher Lee Berger says. The find was a stroke of luck. For nearly two decades, Berger had combed a nearby hill for evidence of hominids when his 9-year-old son, who’d come along on an outing, tripped over a log and shouted, “Dad, I found a fossil.”

Life without oxygen

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Italian scientists have discovered a group of multicellular creatures that thrive without oxygen—a feat previously thought impossible. The creatures, less than a millimeter long, belong to the phylum Loricifera and look something like a cross between a jellyfish and a crab; they were recovered from the sulfurous, oxygen-free, salt-choked sediments 10,000 feet beneath the Mediterranean Sea. “We did not think we could find any animal living there,” Italian biologist Roberto Danovaro tells BBC.com. “We are talking about extreme conditions.” The organisms’ cells lack mitochondria, which all other animals (as well as plants) use to produce energy from oxygen. Instead they contain little power plants called hydrogenosomes, which generate energy from molecules such as hydrogen sulfide. Until this discovery, biologists believed that only the simplest life forms—bacteria and viruses—could survive without oxygen. Scientists now think it’s more likely that multicellular life forms exist in harsh environments on Mars and other planets and moons.

Calling all polliwogs

Next time you toss a rock into a pond, consider this: Tadpoles scream. While studying the adult mating call of the horned frog Ceratophrys ornata, Argentine researchers caught a tadpole of the species in a hand net and heard it emit “a brief, clear, and very audible metallic-like sound,” biologist Guillermo Natale tells BBC.com. Few larvae of any species produce sound. “That tadpoles communicate somehow is simply amazing.” The team grew tadpoles in the lab and confirmed that, in distress (or when prodded with a metal spatula), they emit a series of high-frequency “screams” from their lungs. The larvae are known to eat tadpoles of other frog species but not each other; the scream may serve as a “Don’t eat me!’’ signal to their own species.

A diet to remember

Alzheimer’s disease can’t yet be cured, but a healthful diet may help prevent it, scientists say. A recent Columbia University study found that people who ate a diet rich in nuts, olive oil, fish, poultry, tomatoes, fruits, and leafy green vegetables were 40 percent less likely to develop Alzheimer’s. The study followed 2,100 subjects over age 65 for four years. By the end, 253 subjects had developed Alzheimer’s, but the people least at risk were those who ate less red meat and butter and instead followed a Mediterranean-style diet, which offers more omega-3 fatty acids, vitamin E, and other nutrients that protect the brain. The healthful diet likely works in two ways, study author Yian Gu tells Discovery News: by directly protecting the brain, and by keeping the heart healthy and reducing the risk of strokes, which could render the brain more vulnerable to Alzheimer’s.

The Japanese advantage

People around the world love sushi, but only the Japanese have the guts—or at least the gut enzymes—to digest the seaweed wrapping fully. French scientists recently identified a new enzyme, called porphyranase, that helps marine bacteria feed on certain seaweeds, including nori, which are used to wrap sushi. They pinpointed the genes that code for the enzyme and searched DNA databases to see where else it might appear. Strangely, the gene sequence turns up in a strain of bacterium found solely in the intestines of people of Japanese ancestry. The researchers believe that as the Japanese ate seaweed—and the microbes on it—for several generations, their gut bacteria hijacked the microbes’ genes for the digestive enzymes. The enzymes might help their human hosts extract added nutrition from the seaweed—but unless you already have them, don’t expect to pick them up in your next bento box. “This likely happened back when diets were much less sterile, and the seaweed was teeming with marine microbes,’’ Stanford University microbiologist Justin Sonnenburg tells the Los Angeles Times. “The nori wrappers we find on sushi wraps in the States probably have a lot less microbial burden today.’’

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