Long Tomorrow: How Advances in Evolutionary Biology Can Help Us Postpone Aging
by: Michael R. Rose
Topics include:
From Publishers Weekly
Rose, an authority on gerontology, uses evolutionary biology to frame the problem of aging, contrasting the drive to reproduce in youth with the ability to survive into old age. In short, according to his research, the Victorians were right: sex is death. The evolutionary pressure of reproducing at an early age seems to have the side effect of causing early aging. Rose's explanation of his theory is so clear, it seems ridiculous that anyone could have conceived of another explanation. But whether this theory will ever be used to slow down human aging is unclear. Rose relates the progress of aging research in an autobiographical format. So, interspersed with experiments on long-lived fruit flies, there are almost voyeuristic glimpses into Rose's own life: the suicide of his brother, the murder of his brother-in-law, the tragic end of his first marriage. The result is a book that flops between the evocative stories of one man's life in science and the somewhat drier explanation of that science. Nevertheless, Rose gives a balanced evaluation of the study of aging and sheds a little more light on one of biology's greatest mysteries.
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Reviews:
What we can learn about aging from fruit flies:
This is mostly a memoir about Professor Rose's career as an evolutionary biologist who studies aging in fruit flies and extrapolates that knowledge to humans. The "Long Tomorrow" in the title refers to his belief that "it is still reasonable to hope that eventually the great mass of people will be able to control their aging through pharmaceuticals and medicine." (p. 134)
Rose sees senescence as being the inadvertent product of the evolutionary process. There is no single gene that controls aging. Instead hundreds of genes are involved so that the prospect of a single elixir or technique being developed that would magically postpone aging and death is highly unlikely. Almost as an aside and incidentally, Rose explains why we age and eventually die. His is the standard view that the evolutionary process becomes less and less in force as we get further and further from the onset of our reproductive age until "the force" (as he calls it) is not in effect at all.
This is a very tricky and subtle argument that takes a bit of reflection to fully understand. I know when I first encountered it some years ago I found it hard to follow. It is still very difficult to express. But let me give it a try.
Rose uses the analogy of Ford's Model T automobile. As the story goes Henry Ford wanted to know which parts of his cars almost never wore out. He found out what they were and directed his production staff to make them cheaper so that they would wear out at about the same time as the rest of the car, thereby making his cars cheaper to produce while increasing his profits without decreasing the longevity of his cars. Rose says that nature follows a similar parsimonious production with its organisms. For example, genes coded to allow a body part to last a thousand years would not be selected (or unselected for that matter). Indeed any gene or genes that code for processes lasting past reproductive age would exist in the genome only in a random fashion (if at all). Such genes would randomly appear and randomly die out.
What this means is that after the onset of reproduction everything begins to break down in a more or less random fashion. The environment acts upon us in a multitude of ways. Little insults pile up. Some cells go wildly reproductive and cancers develop. Other cells die due to something we ingested or because of accidents. Microorganisms use our tissues for their reproduction or subsistence (e.g., viral and bacterial infections). Toxicity kills off cells or changes their metabolism so that the cells no longer function properly. Arteries become clogged and blood fails to flow to some tissues which die of starvation...etc. Like Ford's Model T, first one thing goes wrong and then another until finally something stops us from running altogether.
Now, if we can fix one thing and then another and then another, our death can be postponed. If we become very, very good at fixing, death can be postponed for a long time. Such is the argument. The problem is that we are not really good at fixing things that go wrong with our bodies. Most of the fixing that takes place is through the body's own devices. Tissues are repaired, assaults to the skin patched up, bone tissues fused (after being set properly--that we can do). But we can't stop the growth of a cancer that has metastasized throughout the body without killing parts of the body itself. We can't repair a brain that has been deprived of oxygen for more than a few minutes. We can't regrow cartilage that has worn away. And so on.
So the "long tomorrow" will be gradual in coming and the length of that day will grow by small increments.
What I don't understand is this: why isn't the reproductive age of organisms itself indefinite? Or, to put the question another way, why should the young and inexperienced have a reproductive advantage over the old and experienced?
The answer appears to be almost circular in that because older organisms have bodies that are already beginning to break down, they are at a disadvantage to younger organisms whose bodies are in peak form. This is why members of the opposite sex (especially males) choose the young for mates. Or to be more precise, this is why the young are attracted to the young; indeed why all are attracted sexually to those at the peak of their reproductive lives. The young have a longer future and so will be better able to provide for their offspring. The fact that the opposite sex is biased in its choice further accentuates the reproductive advantage of the young.
For a more detailed explanation of why we age, expressed in a different way, see my review of The Biology of Death: Origins of Mortality (2004) by Andre Klarsfeld and Frederic Revah. The point is there is no one-sentence explanation of why we age. It's like trying to explain a complex process in a single phrase. It can't be done.
Those interested in Rose's career (and its ups and downs) and the nature of his work with fruit flies will find this interesting. But for the general reader this book is not the best for understanding why we age and die. There are a number of better books (none of them completely satisfying, by the way). In addition to the opus cited above, here are three others: Austad, Steven N. Why We Age: What Science Is Discovering about the Body's Journey Through Life (1997); Clark, William R. A Means to an End: The Biological Basis of Aging and Death (1999); and Hayflick, Leonard How and Why We Age (1994).