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Why is it that less than 5 per cent of mammal species are monogamous, compared with about 90 per cent of bird species?

Adrian Bowyer,

Foxham, Wiltshire, UK

Having read several recent articles on nutrition and longevity, I wonder how many life-extending cups of tea I must drink to counter the life-shortening effect of eating a hotdog?

Ted Appleyard,

Waterloo, Ontario, Canada

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