Monday, November 10, 2008

What Worry About Aging? (Part 3)

I am in the midst of writing a longer blog post (and new academic paper) on evolution and medicine that deals with the distinction between the proximate and ultimate causes of behaviour and disease.

When preparing that post I came up with the following short story (which in many ways parallels some of the points made in this excellent paper) which I thought it might be prudent to ponder:

Monday morning at 9am Bob left his house for work as he did every weekday. However, he noticed he had a flat tire, caused by a two-inch slash to his front tire. Slightly frazzled, Bob quickly replaced the tire with the spare he had in the trunk of his car. And off he went to work, arriving an hour late.

Tuesday morning at 9am Bob was leaving for work when he noticed that he had a flat tire again! And just like yesterday, a two-inch slash caused the flat. Extremely frazzled, Bob called a tow truck to take his car to the service station. While waiting to get a new tire Bob noticed his neighbour, Jim, was also getting his tire replaced. After a few minutes they realized that Jim’s story was identical to Bob’s. Two flat tires; with two equally sized slashes.

Puzzled by these occurrences they compared notes on where they had driven. Perhaps there was a construction zone close to their street that had lots of nails? But a nail wouldn’t make such a large slash to a tire. Unable to solve the mystery, they went on their separate ways once their tires had been repaired. Bob arrived at work 3hours late.

Wednesday morning Bob was leaving for work when he noticed that he had a flat tire yet again! And so did his neighbour Jim, and all the other cars on his street! The only person who did not have a flat tire was Ted, who lived across from Bob. Bob asked Ted if he knew what caused the two-inch slashes to everyone’s tires but his. Ted suggested it was probably his large pocket knife, which he always used when slashing his neighbour’s tires. "Aha!", thought Bob. That was it. Now he knew what was causing the flat tires.

That evening all the neighbours met at Bob’s house where he revealed the answer to the ongoing mystery. “The flat tires were caused by Ted’s pocket knife!” Bob proudly explained.

“Now what?” wondered Jim.

“I have a plan” replied Bob. And he filled everyone in on his plan to remedy the problem.

Thursday morning Bob awoke extra early. He opened his garage which was now filled with brand new tires. He removed one of these tires and stood by his car.

“Morning Bob” said Ted, as he approached Bob's car with his pocket knife drawn.

“Morning” replied Bob.

Ted then proceeded to slash Bob's tire before casually moving on to the next house. Bob’s neighbour Jim was also waiting for Ted, with spare tire in hand, to quickly change the tire.

“Lucky we bought all these extra tires” remarked Jim as he walked over to Bob.

“That’s right” replied Bob. “Now we will be less inconvenienced by Ted’s pocket knife, the object responsible for all these flat tires”.

And then they went into their respective homes to enjoy breakfast. They were a little tired, and a little more cash-strapped than usual, but not as bad-off as they could have been if they didn’t purchase all those extra spare tires!

The moral of the story: an exclusive fixation on the proximate, rather than ultimate, cause severely limits our opportunities for living flourishing lives. To develop effective strategies that would prevent the massive onslaught of chronic illness humanity is set to experience this century we must devise strategies that seek to redress the ultimate, and not just proximate, causes of disease.

Evolution provides new insights that could help the biomedical sciences devise more effective strategies for promoting our opportunities for health. Rather than prepare by having extra spare tires ready, we should seek to prevent flat tires from occurring by confronting Ted ourselves, or reporting his actions to the police. The knowledge that his pocket knife caused the slash is really of secondary concern (perhaps most useful as evidence in the criminal case against Ted), for it is Ted’s *actions* that are the true cause of the problem. And the solution lies in altering Ted’s behaviour, not in trying to arrange our lives around the inconveniences he causes. Ted is senescence.

While it is not possible to eliminate all the risks of vandalism (or senescence), we ought to at least consider strategies that would minimize the likelihood of these harms being inflicted (like prohibiting vandalism). It is irrational and short-sighted of the neighbours to just accept and live with such harms when there is good reason to believe that other actions would dramatically improve the situation. The current approach to the diseases of aging is like the neighbourhood’s actions. We often fixate on the proximate causes of disease, thus ignoring the evolutionary causes of health and disease. This constrained perspective must be overcome if we hope to meet the challenges facing humanity this century.