The importance of luck in life

As I have got older, I have become increasingly aware of how much luck plays in one’s life, both for good and bad. Looking back, I realize the many, many occasions when it was due to luck that things turned out well or badly for me and I have no reason to think that luck does not play a similar important role for other people.

This does not mean that one’s own efforts and attitudes are not important. They play a significant role mainly in not throwing away the chances that good luck hands you and enabling one to cope with, and recover from, bad luck.

One important area of luck is of course one’s health. And it turns out that when it comes to getting cancer, the role played by luck is greater than one might have thought, as the abstract from this paper suggests.

Some tissue types give rise to human cancers millions of times more often than other tissue types. Although this has been recognized for more than a century, it has never been explained. Here, we show that the lifetime risk of cancers of many different types is strongly correlated (0.81) with the total number of divisions of the normal self-renewing cells maintaining that tissue’s homeostasis. These results suggest that only a third of the variation in cancer risk among tissues is attributable to environmental factors or inherited predispositions. The majority is due to “bad luck,” that is, random mutations arising during DNA replication in normal, noncancerous stem cells. This is important not only for understanding the disease but also for designing strategies to limit the mortality it causes. [My italics-MS]

In the body of the paper Variation in cancer risk among tissues can be explained by the number of stem cell divisions, the authors Cristian Tomasetti and Bert Vogelstein elaborate on their work.

The concept underlying the current work is that many genomic changes occur simply by chance during DNA replication rather than as a result of carcinogenic factors. Since the endogenous mutation rate of all human cell types appears to be nearly identical (23, 24), this concept predicts that there should be a strong, quantitative correlation between the lifetime number of divisions among a particular class of cells within each organ (stem cells) and the lifetime risk of cancer arising in that organ.

To test this prediction, we attempted to identify tissues in which the number and dynamics of stem cells have been described. Most cells in tissues are partially or fully differentiated cells that are typically short-lived and unlikely to be able to initiate a tumor. Only the stem cells—those that can self-renew and are responsible for the development and maintenance of the tissue’s architecture—have this capacity. Stem cells often make up a small proportion of the total number of cells in a tissue and, until recently, their nature, number, and hierarchical division patterns were not known.

Through an extensive literature search, we identified 31 tissue types in which stem cells had been quantitatively assessed (see the supplementary materials). We then plotted the total number of stem cell divisions during the average lifetime of a human on the x axis and the lifetime risk for cancer of that tissue type on the y axis.

The correlation between these two very different parameters—number of stem cell divisions and lifetime risk—was striking, with a highly positive correlation (Spearman’s rho = 0.81; P < 3.5 × 10-8). Pearson’s linear correlation 0.804 [0.63 to 0.90; 95% confidence interval (CI)] was equivalently significant (P < 5.15 × 10-8). One of the most impressive features of this correlation was that it extended across five orders of magnitude, thereby applying to cancers with enormous differences in incidence. No other environmental or inherited factors are known to be correlated in this way across tumor types.

The wrong lesson to draw from this study (assuming that the finding holds up in later work) is that we do not need to worry that much about carcinogens in the environment and in food and cigarettes. We should definitely continue to reduce our exposure to such things. But it does mean that those of us who try to live healthy lives and yet develop cancer may be just the victims of bad luck and there is no point wringing our hands and second-guessing ourselves by thinking that we did something wrong.

The authors say that their work may shed some light on which types of cancers are most likely to respond to preventative treatments. Jennifer Couzin-Frankel writes more about the paper.


  1. machintelligence says

    As Rincewind noted in the Discworld series: “Luck is my middle name…unfortunately my first name is Bad.”

  2. mnb0 says

    Over at PZ’s blog there is a similar article.

    “This does not mean that one’s own efforts and attitudes are not important.”
    Of course they are – you just have to maximize your chances if you want something. Since I realized this this principle has served me well.

  3. says

    I was listening to Baz Luhrman’s “everyone is free to wear sunscreen” and something about how he phrased it really made it click:

    what ever you do, don’t
    congratulate yourself too much or berate yourself either – your
    choices are half chance, so are everybody else’s.

    My whole life I’ve been interested in the problem of free will and opportunity and randomness and I didn’t really feel I “got it” until then. Sure, I can pat myself on the back when I do something clever but I need to remember that the situation in which I was clever was almost completely out of my control and that all I could do was the best I could with the situation as it presented itself. And so does everyone.

  4. doublereed says

    Luck determines your geography, family situation, community, educational opportunities, physical environment, genetics, etc. etc. All things that you simply have no control over initially.

    I’ve heard many, many people deny the importance of luck, because Just-World Hypothesis is such an important notion to all conservative thought.

  5. says

    “Luck” doesn’t exist, chance does. Genetic traits are out of our control, but many things that affect our health are well within our control, and it’s folly not to make the effort and try. Lung cancer in a person who smoked for thirty years is not “unfair”, it’s cause and effect. Leukemia in a ten year old child is unfair.

    Most who are “lucky” were so because of hard work, talent and preparation (e.g. people in their school and work careers, sports teams), and such success is repeatable. Yes, there are outliers (lottery winners, hockey and soccer teams with a hot goalie) but they are rare and unpredictable exceptions.

    It’s the same with health. Those who eat healthy, exercise regularly and avoid dangerous lifestyles (toxic workplaces, drugs, etc.) tend to live long lives. Those who use drugs, are sedentary, eat garbage and “live on the edge” tend to have shorter lives. Again, there are outliers (e.g. Joe Cocker’s recent death at 70 despite his drug use versus Frank Zappa’s early death at 53 despite living clean) but they are exceptions. The majority of people have health and lifespans that compare with their lifestyles.

  6. Dunc says

    Frank Zappa’s early death at 53 despite living clean

    Dude, Zappa practically lived on cigarettes. Hell, one of his most famous quotes is “To me, cigarettes are food.” And yet, it was prostate cancer that got him in the end. How’s that for luck?

  7. says

    “Luck” doesn’t exist, chance does.

    Luck is probability taken personally (Penn Jillette)

    Aaaaand that’s about the one thing of Penn’s that I agree with. Yes, there is such a thing as “luck” – it’s how an individual interprets chance events in their own context. “You were lucky” means I think that chance worked in your favor on a given set of events. And I could be completely wrong. “Luck” is real but only in the sense that our opinions are real.

  8. says

    Dunc (#6) –

    Okay, I was misinformed. I was only passingly familiar with his work, and never saw a picture of him smoking. What I remembered was interviews around the time of his death, his anger for having cancer while drug users lived on.

  9. Ms. Ann Thrope says

    On “luck”
    Luck certainly does exist and it is one of three traits that you need to be successful and/or happy; the other two being ability and passion. And furthermore, it is the most important element of the three. I should know. I am widely considered to be the best in the world at what I have done. In my field I had all 3 traits in spades. However, in the last 5 years my personal life has been like a living hell. A stepdaughter who put a wedge in a thirty year marriage and an enabling wife, 4 friends of between 30-50 years betrayed me. 2 partners in two other businesses cheated me and health issues. And luck is most important of the three traits due to simple mathematics. Example is you can have all of the ability and passion in the world but if you are in a plane going down; game over. Alternatively if you have luck; this can incorporate a genetic recipe and benevolent childhood which fosters and nurtures ability and passion. Free Will is at best a relative term and at worst an oxymoron.

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