Lamarck’s Last Laugh?

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Jean Baptiste-Lamarck (1774-1829) 

Lamarck theorized that traits acquired during one’s lifetime could be passed along to subsequent generations.  His theory was discredited, but recent studies in the field of epigenetics may at least partially vindicate Lamarck.  Specifically, research suggests that environmental exposures could leave a lasting imprint affecting future generations. 

When French biologist Jean-Baptiste Lamarck died in 1829, his remains were thrown into a lime-pit along with the remains of other poor and anonymous Parisians.  Lamarck died poor, and his theories on evolution were actively discredited by his peers.  Lamarck theorized that traits acquired during one’s lifetime- or traits we would now attribute to "nurture" (as opposed to "nature")- could be passed along to subsequent generations.  One common example of Lamarckism (as his theory is called) is that of a father who exercises or works strenuous labor- Lamarck believed that the physical benefits of such exercise or labor could be passed along to subsequent generations. 

Eventually Charles Darwin’s views on evolution and Gregor Mendel’s experiments on heredity supplanted Lamarckism.  Today the prevailing paradigm is that traits are passed along via genes, and that "nurture" (ie our habits and environmental exposures) have minimal lasting (or heritable) impact on genes (nature).

However, contemporary research in a field known as “epigenetics” reveals that environmental factors do impact our “nature,” and in a way that may be heritable.  Epigenetics is a burgeoning field of science investigating the mechanisms by which genes are switched on and off.  Increasingly scientists are learning that much human variability can be attributed to regions outside of genes.  Specifically, non-gene regions of DNA, as well as molecular tags (ie “methyl” groups) and proteins associated with DNA (ie proteins called “histones”), help regulate DNA (ie by turning genes on and off).  In sum, the epigenome likely contributes to many of our traits and health.   

Your Current Health May Be Partially Attributed To Your Ancestors' Habits and Exposures

Note a perplexing phenomenon: lung cancer rates in non-smokers appear to be increasing.  One scientist explains this trend with a provocative theory- some lung cancers in non-smokers may be attributed to our ancestors’ chronic smoking.  Specifically, Dr. Spector notes that chronic smoking might alter one’s epigenome (non-gene DNA and/or associated tags and proteins) in a way that is heritable (can be inherited).  

The revelation that disease states can be attributed to non-gene elements is surprising enough.  Additional evidence also suggests that alterations to these non-gene elements may be passed along to future generations. 

For example, a study showed that pregnant mice ingesting BPA were more likely to give birth to unhealthy and obese offspring (BPA is a chemical used to make types of plastic).  And associated with these changes were epigenetic alterations. 

A recent study also demonstrated that exposure to the chemical “tributylin” (found in PVC pipe) led to obesity in mice.  Incredibly, the children, grandchildren, and great-grandchildren of the mice also appeared at risk for obesity even though none of these mice were directly exposed to the chemical.

A 2005 study looking at a group of children in Sweden noted that the habits of fathers and grandfathers appeared to impact the health of the children.  Specifically, researchers found that grandfathers who experienced food shortages in their childhood tended to have grandchildren who lived longer.  Also, fathers who smoked tended to have children with higher body mass indexes (BMI).

What does this all mean?

If further studies in epigenetics show that environmental changes can leave a heritable imprint upon one’s “nature” (ie one’s epigenome), this would partially validate Lamarck's notion that acquired changes are heritable.

Also, in a very general sense, these studies demonstrate that deciphering the “human genome” is likely much more complicated than anticipated.  Specifically, non-gene elements in DNA impact human variability and health, and some of these non-gene elements may be subject to alteration by our ancestors’ habits and environmental exposures.  In the near future, expect scientists to continue to explore the epigenome.  It will be interesting to note if any additional studies reinforce the hypothesis that environmental factors leave a heritable impact upon our epigenome.

Related:

  1. Interesting article The Age of Epigenetics by Dr. Tim Spector (mentioned in the article above)
  2. Other BiG articles on the Human Genome & Epigenetics

Updates

January 28, 2013:  

Within a few days of publishing "Lamarck's Last Laugh," I came across several other relevant and interesting articles on recent breakthroughs in epigenetics:

February 3, 2013: 

For an an additional and wonderfully comprehensive discussion of epigenetics, consider reading Reuters' recent "Special Topic: Epigenetics"

February 10, 2013:  

Yet another popular article on epigenetics- this one in the Washington Post and titled Genetic reactions to stress might be felt in later generations, mouse studies show.

See also a recent study on mice suggesting that nicotine has a "multigenerational" effect on lung function (ie rats whose parents "smoked" experienced poorer lung function despite the fact that these rats were never directly exposed to nicotine).

February 18, 2013:  

  • Another article titled "Effects of Stress Can Persist for Generations" discusses a recent study whereby researchers induced significant stress in mice and found that future generations of mice appeared more anxious than control mice, and the study authors hypothesize that anxious behaviors appear to have been transmitted across generations.   
  • Life experiences put their stamp on the next generation:  Article describes associations mentioned above between parental experiences (ie stress) and child's predispositions to fear & stress.  The article even begins by explaning these observations in the context of Lamarck.  

March 29, 2013:  

  • Obesity tied to DNA Regulation.  Body mass index (BMI) and other environmental factors likely have an impact on the way genes are expressed.  
  • Smoking's Genetic Impact Lingers.  Smoking is linked to gene expression changes, some of which appear to persist after quitting, researchers found.  Note we do not yet know precisely the magnitude or even the consequences of such changes, but the idea that environmental factors impact DNA (in a manner that is likely heritable) was previously less accepted when Big In Science noted it in the article above ("Lamarck's Last Laugh").  

April 22, 2013:

This two-day conference highlighted some of the major areas of investigation in this relatively young field, in particular the observance that acquired traits, mediated through epigenetic effects, can be passed onto offspring in a rather Lamarckian fashion.