The human species has increased its life span by ______.

W: The quest for immortality has been a past and a current obsession. How will medical advances contribute to longer life spans? Is there a limit to how long we can live?
M: In the 20th century, in the developed nations, our life span increased from about 50 years to about 80 years. In just 100 years, our species increased its life span by 60 percent. Right now changes in our lifestyle have more power to extend our life span than any medicines yet invented: sitting around waiting for a magical life-extending cure-all isn’t healthy. Still, there have been some remarkable advances in identifying genes that affect aging. Manipulating those genes extends the life spans of some simple animals by 500 percent. I think our grandchildren may see a word in which people live healthier and considerably longer. But I won’t be there to find out if I was right.
W: Are the dangers of advancing medicine too far ever taken into consideration? What happens when there is no more sickness and people live so long that we overpopulate the planet? How far is too far?
M: I agree with you that longer lives and larger populations could cause problems. This is particularly true in overpopulated parts of the world, where hundreds of millions of people live in hunger and squalor. While discovering how to extend the healthy human life span, we also need to make major advances in cheap energy and food production. Otherwise we risk making the problems of overpopulation and uneven distribution of resources even worse.
W: How can we control harmful viruses when they seem to change more quickly than medical and research advances?
M: It is getting tougher for humans to fight viruses. Viruses counter our moves against them. They multiply very rapidly, and occasionally a genetic mutation occurs that allows them to resist our antiviral drugs. However, scientists are working on entirely new strategies. For example, a recently discovered natural process called RNA interference has shown early promise in treating viral infections. Like viruses, bacteria are also becoming more difficult to treat. Ironically, one way of countering bacteria may be to harness a group of viruses known as bacteriophages. For millions of years, these viruses have been killing specific bacteria without harming humans. Scientists are examining whether bacteriophages, rather than antibiotics, might help treat some bacterial infections.
W: What is the status on finding a cure for HIV/AIDS?
M’ It is now 25 years since HIV/AIDS was first recognized, and we do not have either an effective vaccine or a curative antiviral treatment. Yet treatment has improved dramatically: For many people, HIV/AIDS is now a chronic disease and not a death sentence. Why don’t we have a cure? One problem is that today’s treatments, while suppressing HIV’s ability to proliferate and damage organs, do not completely eliminate the virus from the body.
W: Obesity seems to foster just about every other malady known to man. What’s down the road in the field of DNA research and drug therapy?
M: Obesity surely does make us more vulnerable to many major diseases, including heart disease and diabetes. No matter what great advances science offers, a healthy diet and regular exercise will always contribute to the maintenance of a healthy weight. That said, over the past 15 years scientists have discovered a group of genes that powerfully influence hunger and the efficiency with which we bum calories. It really is true: some people are born with "thin" genes. As we figure out how certain genes make it easier to be thin, I am optimistic that within the next 20 years we will develop new drugs that help us achieve a healthy weight without serious side effects.
W: How must medical training change to meet the future challenges of health care?
M: To be a good doctor, you have to know a lot of facts. Medical training does a very good job of teaching those facts. But a good doctor also needs to have many other skills: to keep up with an ever-changing body of medical knowledge; to learn how to make decisions such as how to balance the benefits of a test or treatment against its risks; to sense a patient’s unexpressed fears or misunderstandings, and, above all, to care. It is a lot harder to teach these skills than to give medical students facts to memorize. At our medical school, and at many others, the curriculum is being changed to emphasize such skills.
W: The delivery of health care varies widely in this country, and medical errors cause a lot of unnecessary injury. How, going forward, will doctors be trained in the uniform practice of medicine?
M: Scientific medicine has given us outstanding technologies for diagnosing and treating disease, but doctors and hospitals do not always practice scientific medicine. Sometimes tests or treatments are ordered when their risks exceed their benefits. Other times, tests or treatments are not ordered when scientific studies say they should be. These departures are sometimes justified by a patient’s wishes or a doctor’s clinical judgment. Unfortunately, they occur more often because there are no systems in place to monitor practice and maintain quality. We need many more systems to encourage scientific medicine, while leaving room for justified exceptions to the rules.