The Solar-powered Solar Impulse 2 aircraft prepares to take off from the Cairo International Airport in the Egyptian capital on Sunday as it heads to Abu Dhabi on the final leg of its world tour. Khaled Desouki /AFP/Getty Images hide caption

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Yao honey hunter Orlando Yassene holds a male greater honeyguide temporarily captured for research in the Niassa National Reserve, Mozambique. The birds will flutter in front of people, tweet and fly from tree to tree to guide hunters to bees' nests that are hidden inside the trunks of hollow trees. This teamwork could date back thousands or even a million years. Claire Spottiswoode hide caption

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How Wild Birds Team Up With Humans To Guide Them To Honey

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The physical therapy workouts a rehabilitation facility offers can be a crucial part of healing, doctors say. But a government study finds preventable harm — including bedsores and medication errors — occurring in some of those facilities, too. Andersen Ross/Blend Images/Getty Images hide caption

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Grains, beads and bangles unearthed from dig sites in Banda, Ghana, tell of a time when droughts did not bring famine. (Above) Archaeologists Amanda Logan and Osei Kofi dig into the floor of a house from the 1500s. Courtesy of Ann Stahl/Northwestern University hide caption

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Peter Lee, executive director of Covered California, the state's health insurance exchange, said the projected rate increases for 2017 are linked to increases in the cost of health care in the state. Rich Pedroncelli/AP hide caption

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Can Big Data Help Head Off Police Misconduct?

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'Ban The Box' Laws,' Do They Help Job Applicants With Criminal Histories?

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Ovarian tissue after the thaw — ready for reimplantation. Courtesy of The Infertility Center of St. Louis hide caption

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Twin Sisters Try To Get Pregnant With Ovaries They Froze In 2009

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Breasts deemed "dense" in a mammogram tend to have less fatty tissue and more connective tissue, breast ducts and glands, doctors say. About 40 percent of women between the ages of 40 and 74 have dense breasts. Lester Lefkowitz/Getty Images hide caption

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Zika virus particles (colored purple in this scan) infecting cells. Each particle is about 40 nanometers in diameter. CDC/Smith Collection/Gado/Getty Images hide caption

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A Case Of Zika Apparently Spread From A Patient To A Family Caregiver

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