We’re only human

By Dr ALBERT LIM KOK HOOI

Genes, experience, and limited free will – what is it that makes us human?
THANK you for being such an attentive audience. Dr. Lim, I am sure, will be only too happy to take questions.
The chairman’s remarks are made after a round of polite applause. I have just concluded another public lecture on the theme, Prevention of Cancer, and I brace myself for questions.
Inevitably, like death and worsening climate change, one hand shoots up. “Doctor, my grandpa smoked two packs of cigarettes a day for 50 years and he did not contract lung cancer. Yet I know of many non-smokers who have been diagnosed with lung cancer. Your comments doc?” Sometimes, the question is laced with cynicism and swagger. Sometimes it is asked rhetorically, as if to say we should all smoke, eat, and drink with gay abandon.
I scan the two hundred eager faces awaiting my rejoinder. I know the lecture hall is not the time or place to speak of the genome, the epigenome, and the question of nature versus nurture. Instead, I usually entertain my listeners with one of my parables about risk.

Epigenetics can help explain certain scientific mysteries, such as why one of a pair of identical twins can develop a certain disease, such as asthma, even though the other is fine. –Reuters

“Let us say you drive home from work in a car designed and made in the continent. And let us say you comply with the highway code in its entirety. You haven’t had a drink for the last 24 hours. You have no worries about your job or family. The roads are clear and dry. The chances are you will arrive home safely, although an accident is not completely ruled out.
“On the other hand, your blood alcohol limit has been exceeded, your car is long overdue for a service, the roads are wet and you text a message to your irate husband as you drive. You may still arrive home in one piece, but your chances of meeting an accident are greatly enhanced.
“Ladies and gentlemen, we are speaking of risk and how we can increase or decrease it. Life is probabilistic and many scientific endeavours are devoted to lowering your risk of a premature death or suffering a disease or disability. Think of all the effort put into road and other transport safety, advice on what to eat and what to avoid, vaccinations, occupational safety, global warming, prediction of earthquakes, and tsunamis.”
This usually satisfies the audience ... until the next lecture when another hand shoots up and I hear the inevitable, “Doctor, my grandpa ...”
Risk and probability in the human context is underpinned by the nature/nurture question. For the last hundred years, scientists and thinkers have pondered the question of nature versus nurture. How much of our bodies, minds, personalities, traits, and abilities are a result of our genes, ie determined by what we inherit from our parents? How much is a result of the environmental forces we are subjected to from the time we are conceived? How much do our childhoods and teenage experiences matter?
Things began to change just over a decade ago. We realised that it was no longer nature versus nurture, but rather nature via nurture. In other words, we are no longer slaves to our genes. Neither can manipulating the environment shape us this way and that like a pretzel. Rather, it is that our genes can be switched on and off by our environment.
We also realise that with whatever limited free will we have, we can strive to realise the full potential of our genes by sheer perseverance, practice, or a change in our lifestyles.
We now add another dimension to the nature (DNA, genes), nurture (environment) equation. It is epigenetics. Genes provide the codes to build proteins which determine how we are built and how we function, at least to a first approximation.
Epigenetic marks (mainly the methyl group, CH3, but there are others) sit atop genes and offer basic instructions to them, telling them to switch on and off. Environmental factors, like a rich diet, can activate epigenetic marks, which can in turn modify our DNA. There, changes can turn our genes on or off.
Epigenetics could also help to explain certain scientific mysteries that traditional genetics never could. For instance, why one of a pair of identical twins can develop bipolar disorder or asthma even though the other is fine. Or why autism strikes boys four times as often as girls. Or why your grandpa smoked and smoked to a coughing fit and never contracted lung cancer while some other non-smoker died of lung cancer in her 40s.
It all comes down to one basic question that has vexed humanity since antiquity. How much of our life has already been determined when we are born and how much is within our control? I am optimistic that science will uncover more about this conundrum in the coming years.
In the meantime, try to quit smoking and drive safely. You have more, and less, free will than you think.
Dr Albert Lim Kok Hooi is a consultant oncologist. For further information, e-mail starhealth@thestar.com.my. The views expressed are those of the writer and readers are advised to always consult expert advice before undertaking any changes to their lifestyles. The Star does not give any warranty on accuracy, completeness, functionality, usefulness or other assurances as to the content appearing in this column. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.

source:http://thestar.com.my