Do We Really Want Eternal Life?
幻城插曲
Are you hoping for a long life? Thought so. Are you looking forward to growing old? Thought not. Men have wanted one without the other for thousands of years, and have invariably been disappointed. The Spanish explorer Juan Ponce de Leon was more famous for his arch for the Fountain of Youth than for discovering Florida in 1513. He never did find the spring that the natives had told him of, and perished from a poisoned Indian arrow a few years later.
The legend of the Fountain of Youth may have originated in northern India. It had reached Europe by the 7th century, and was widely known there in the Middle Ages. One painter painted a famous picture of the fabulous spring, with wrinkled old women going in at one end and young beauties coming out at the other. Writers have constantly imagined worlds where people lived to extraordinary ages while holding on to their youthful looks and vigor by various means, mostly foul. In the real world too, people are tempted to try all kinds
氧化铁和稀硫酸反应of disgusting things, from bathing in tubs of warm mud to receiving injections of monkey glands, all in the hope of foiling the negative effects of ageing.
Though the probability of living to old age has rin sharply, the individual human lifespan t by nature has remained much the same through most of recorded history. It was — even if mainly in theory — 70 years at the time the Bible was written, and it isn't much more now. Most people died of one thing or another long before their maximum span was up. 如何瘦腰
The big achievement of modern times is that, in developed countries at least, most people are now well enough off to reach the age they were designed for. No longer do they die in large numbers in the first year of life, or later from infectious dias and medical problems such as a ruptured appendix, or suffer from hunger, or work themlves to death. Barring accidents, most people now go on until they die of one of the dias that afflict the old, such as heart dia or cancer.
The current emphasis in age rearch is on finding ways to ensure that the rising num
ber of people who achieve the maximum lifespan do so in optimum health, not just die after extra years of chronic illness and decay. Much of the advice handed out is simple common n: adhere to a healthy lifestyle, eat and drink in moderation, do not smoke, take regular exerci but don't overdo it. The rules are often ignored, sometimes without apparent ill effect. In a speech at his 70th birthday celebration, Mark Twain outlined his own survival strategy:
层出不穷意思
"I have made it a rule to go to bed when there wasn't anybody left to sit up with; and I have made it a rule to get up when I had to. In the matter of diet, I have been persistent in not eating the things that didn't agree with me, until one or the other of us got the best of it. I have made it a rule never to smoke more than one cigar at a time. As for drinking, when others drink I like to help. I have never taken any exerci, except sleeping and resting, and I never intend to take any. Exerci I despi."
黄花梨水果
He lived to 75. In 1910, that was much longer than most Americans.
红色角落 But even for tho who stick to the rules, all that a healthy lifestyle can do is to improve
奶盖的做法
当然退伙their chances of staying in reasonable shape for their age; it will not slow down the ageing process. And despite all the advertising, none of tho highly profitable patented remedies so widely marketed nowadays can achieve this either, at least not for now. The only experiments on laboratory animals that have definitely shown a life-lengthening effect have involved subjecting rats and mice to a verely restricted diet. The fewer calories they eat, short of actual starvation, and the longer they go on doing so, the longer they live. But they pay a price; starving rats reproduce less, and starving mice don't reproduce at all.
A different approach might work. To some extent long life is an inherited trait. Experiments with that old friend of science, the fruit fly, have shown that mating flies with long lifespans can produce significantly longer-lasting descendants. But again, that would not be much help to humans: we have long life-cycles, so the results might be centuries ahead — even were we ready to choo potentially long-lived mates rather than beautiful or wealthy ones.
What, though, if instead of lective breeding for longer-lived descendants, we were to manipulate our genes? Now, all sorts of gene therapy treatments are beginning to look promising. The process of ageing is a complex matter in which many different genes appear to be involved, but in time it may become possible to u gene therapy to slow down ageing, if not eliminate it.
