Perhaps nothing is more unexpected about our brains than that they are smaller today than they were ten or twelve thousand years ago, and by quite a lot. Specifically, the average brain has shrunk from 1500 cubic centimetres then to 1350 cubic centimetres now.
An elephant's heart beats just thirty times a minute, a human's sixty, a cow's between fifty and eighty, but a mouse's beats six hundred times a minute — ten times a second. Every day, just to survive, the mouse must eat about 50 per cent of its own body weight. We humans, by contrast, need to consume only about 2 per cent of our body weight to supply our energy requirements. One area where animals are curiously — almost eerily — uniform is with the number of heartbeats they have in a lifetime. Despite the vast difference in heart rates, nearly all mammals have about 800 million heartbeats in them if they live an average life. The exception is humans. We pass 800 million heartbeats after twenty-five years, and just keep on going for another fifty years and 1.6 billion heartbeats or so. [...]
For most of our history, 800 million beats per lifetime was about the human average, too.
The fruits that Shakespeare ate were, for the most part, probably no sweeter than the modern carrot.
As Harward physiologist Lawrence Henderson famously remarked: ‘Somewhere between 1900 and 1912. a random patient with a random disease, consulting a doctor chosen at random, had for the first time in history a better than fifty-fifty chance of profiting from the encounter.’
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Two things can be said with confidence about life expectancy in the world today. One is that it is really helpful to be rich. If you are middle-aged, exceptionally well off and from almost any high-income nation, the chances are excellent that you will live into your late eighties. Someone who is otherwise identical to you but poor — exercises just as much, sleeps as many hours, eats a similarly healthy diet, but just has less money in the bank — can expect to die between ten and fifteen years sooner. That's a lot of difference for an equivalent lifestyle, and no one is sure how to account for it.The second thing that can be said with regard to life expectancy is that it is not a good idea to be an American.