Charles, Prince of Wales, smells before tasting some ice cream during a visit to Gloucestershire. Maybe he was sniffing for fat? Barry Batchelor/Getty Images hide caption

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A new study on lactose tolerance among early farmers in Spain challenges a leading theory that humans developed an appetite for milk to avoid calcium deficiency. iStock hide caption

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Say aaaaaah! Dental caries and other signs of oral disease are plain to see in the upper teeth of this hunter-gatherer, between 14,000 and 15,000 years old. The findings challenge the idea that the original paleo diet was inherently healthy, says paleo-anthropologist Louise Humphrey. It all depended, she says, on what wild foods were available. Courtesy of Isabelle De Groote hide caption

itoggle caption Courtesy of Isabelle De Groote

A display of a series of skeletons showing the evolution of humans at the Peabody Museum, New Haven, Conn., circa 1935. Hulton Archive/Getty Images hide caption

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Humans and chimpanzees — like this individual at a zoo in Australia — are animals who have evolved to forge extensive and elaborate social connections. Lisa Maree Williams/Getty Images hide caption

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The Cathedral Spires in the Black Hills of South Dakota are just one of innumerable formations across the planet that speak to the Earth's ancient history. K. Scott Jackson/Ohio Water Science Center/USGS hide caption

itoggle caption K. Scott Jackson/Ohio Water Science Center/USGS

The plate on the left contains about equal numbers of colonies of two different bacteria. After the bacteria compete and evolve, the lighter ones have taken the lead in the plate on the right. Courtesy of Michael Wiser hide caption

itoggle caption Courtesy of Michael Wiser

The first taste of an olive can be a bit shocking. But eventually, many of us start to enjoy bitter fruits, nuts and beverages. Screenshot from TEDxTalks/Youtube.com hide caption

itoggle caption Screenshot from TEDxTalks/Youtube.com

Human evolution is an unfolding process with chapters yet to be written; no one really knows where we're going. But we can look back to earlier chapters, with ancestors like Australpithecus afarensis, including the individual we call "Lucy" (seen above), for an understanding of how evolution works and what has happened to us over time. Tim Boyle/Getty Images hide caption

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