Study shows dolphins develop Alzheimer's - that's bad news for extending human lifespans

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We've long praised dolphins as being one of the most intelligent animals on Earth, but that might come with an unfortunate downside. Oxford researchers studying the brains of dolphins have found clear signs of Alzheimer's disease, marking the first time the illness has been detected in a wild animal. In an interesting twist, the discovery may dash the hopes that an extreme calorie-restricted diet can extend our lifespans. In most cases, animals die soon after they become infertile with age, because – in the eyes of evolution – once a creature passes on its genes, what's the point of keeping it alive? A handful of species, including humans and dolphins, can live long post-fertile lives, but conditions like Alzheimer's and diabetes might be the price we pay for those twilight years. Testing that idea was the focus of the new study, and to do so, the researchers looked at the brains of dolphins to see if these long-living creatures also exhibited signs of Alzheimer's. The specimens were found in the wild in Spain, having died after becoming beached. Sure enough, the researchers found plaques and tangles in the animals' brains – classic calling cards of Alzheimer's. Plaques are deposits of a protein called beta amyloid that build up between neurons, while twisted strands of a protein called tau make up the tangles. Together, these intruders choke out nerve cells and cause the deterioration we know as Alzheimer's.

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"It is very rare to find signs of full-blown Alzheimer's disease in non-human brains," says Simon Lovestone, lead researcher on the study. "This is the first time anyone has found such clear evidence of the protein plaques and tangles associated with Alzheimer's disease in the brain of a wild animal."

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According to the new study, the life-extending benefits of caloric restriction might not translate to humans – nature has likely wrung out all the extra years of life that such a drastic diet could offer. "If we are right, then it is already too late, by tens of thousands of years," says Lovestone. "That's about how long ago in our evolution we are likely to have acquired the insulin resistance that gained the extended lifespan that calorie restriction would produce. While a sensible diet has obvious health benefits and is important for avoiding premature death from avoidable obesity-related conditions, we think that extreme calorie restriction will not extend the human lifespan."

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