If you look at the human body it is easy to understand the purpose of each part and to note how well designed it is. Our hands are beautifully adapted for grasping, and our eyes offer a full-color, three-dimensional view of our surroundings. Even our feet, curiously large and flat by animal standards, are just what we need for bipedal standing and walking.

Some of our features, true enough, are not much good today, but we can see how useful they must once have been. Fingernails and toenails are not great as claws (though trying to open a pen- knife just after you have trimmed your nails) but long ago they must have served that purpose. Body hair is mostly covered or removed, although head hair is still esteemed largely for cosmetic reasons. Although body hair does little to retain body heat, or protect us from attack, once it did both. Even the appendix, which today is at best useless and at worst life-threatening, must once have served a function.

That takes care of most of our bodies, although occasionally I still wonder why our ears have their peculiar and complicated shapes. Matters become less simple when we consider the functions of our brains. Some things, again, seem more of ancestral than current value. Pain, which originates everywhere except in the brain (which has no pain sensors) but whose signals are interpreted exclusively within the brain, no doubt developed as a warning that the body was being damaged. As an accompaniment to drawn-out terminal disease, however, it is something we could all gladly do without.

What about memory? The simple answer is to quote George Santayana, "Those who cannot remember the past are condemned to repeat it." In other words, by remembering how we got into difficulties or danger, we will (we hope) avoid them in the future.

This idea assumes two things. First, that we will remember and be able to differentiate between good and bad past experiences, although people often say that during moments of blind panic they observe and remember nothing at all; and second, that after those good or bad experiences we will employ the information gained to improve our future actions. I am reminded of Dudley Moore interviewing Peter Cook, after the latter had opened a disastrously unsuccessful restaurant: "And have you have learned from your mistakes?" "Oh, yes, and if necessary I could repeat them exactly."

Much has been written about the mechanism of memory, and how short-term memory is converted to long-term memory. Less consideration has been given to the reasons for the existence of memory - why do we remember things at all, and why do we forget?

In case this seems too obvious to warrant discussion, I want to offer thoughts which I have not found in standard works, such as Steven Pinker's "How the Mind Works" or "The Oxford Companion to the Mind" (both highly recommended). Let me begin with a couple of sayings: "You can't teach an old dog new tricks." "He doesn't have thirty years of work experience; he has one year, repeated thirty times." Second, let us note that humans are the longest-lived of all the mammals. Certainly, in our first five or six years we learn many of the ingredients necessary for basic survival. "Don't eat or drink this" (it's poisonous); "Don't touch that" (it's hot); "Don't try to fly out of your bedroom window" (I can make a case that Peter Pan ought to be banned as children's entertainment). But do we learn much after that? Examples of human folly can be drawn equally from all age groups, although the nature of the folly changes.

This brings me to my main thesis. We consider it our right as humans to remember all of our past life, except for very early childhood. I see no reason to regard this as either necessary or desirable. There is no reason why we should remember all that happens to us. A hundred and fifty years ago, life expectancy in this country was about forty. Someone born here today has a good chance of reaching twice that age. Evolution presumably optimized our memory for the shorter life span. But our world, and what it takes to survive comfortably within it, change fast. A memory which remained sharp for events of the past twenty years, but in which more distant events faded unless they were periodically refreshed by recent encounters and events, would please me far better than my crystal-clear recollection of my first day at school, and it would be far more useful. It would, for example, allow me to remember the names of people I met at lunch last week.

Is it unthinkable that we might one day be able, through medications, to change the type of memory from the one I have to the one I wish I had? It's not unthinkable, since I just thought it, but I don't believe it is likely until the tinkering that we do to ourselves can go deep into brain functions that current medications are unable to touch.

At lunch today, I asked, "Do you think that a butterfly has any memory at all of its existence as a caterpillar? Does an oyster perhaps dream of those happy free-swimming days of youth, before it settled to a sessile existence on the seabed?" The look I received, suggesting that I had perhaps become deranged, was not unreasonable. However, I believe that I can answer those questions myself. The butterfly and the oyster remember nothing of their former phases of existence, because those memories would have no survival value whatsoever.

But maybe I am wrong. Maybe the butterfly and the oyster are more like me than they seem. Perhaps the butterfly remembers clearly that dreadful day when the caterpillar incarnation of its early self felt an irresistible urge to smother its body in strands of silk, and hang itself in a place where it could be picked off by any passing bird or spider.

I still wonder what possible benefits I derive from the painful and embarrassing recollection of my first day at school. It is certainly not because I am ever going to tell anyone what happened.

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