Prior to Charles Darwin, many scholars, including Darwin’s grandfather Erasmus Darwin, believed that organisms evolved over time, becoming more complex and better suited to their environment. But the key question was how did it happen? One of the most respected ideas prior to Darwin’s theory of natural selection was that of Jean-Baptiste Lamarck, who argued for the inheritance of acquired characteristics.
This was the idea that the experiences of an organism would influence its off-spring. From this perspective, giraffes, by virtue of stretching to get higher leaves who have offspring with longer necks, and Arnold Schwarzenegger’s children, by virtue of all the iron he pumped, would be stronger than average.
Darwin’s theory of natural selection was different than Lamarck’s. Instead of claiming that life experiences would influence subsequent generations, Darwin’s theory was that there somehow was variation at the level of inheritance, and it was this variation that was the “fuel” for the evolution of organic complexity. Although this variation would influence the likelihood that organisms would eventually reproduce, according to Darwin’s perspective the actual content of their lives would not change the nature of the material inherited. When Gregor Mendel’s work on genetics provided precisely the kind of material that Darwin’s theory proposed, it seemed clear to biologists that Darwin’s theory was right and Lamarck was wrong, and the modern evolutionary synthesis, the great biological achievement of the 20th century, was born.
However, perhaps not unlike what happened with Newton’s ideas during the turn of the 20th Century with the emergence of quantum mechanics and general relativity, the turn of the 21st Century is beginning to raise serious questions about the completeness and accuracy of the modern synthesis. This is due in part to the field of epigenetics, which has really caught fire in the past decade or so. Although there is some dispute about the technical definition of epigenetics, it basically refers to elements outside of the genome that regulate how genes are expressed or become active or inactive. It used to be thought that the genome was fairly static. And while it is true that the basic content of the genetic code does generally stay the same, biologists now know that development and experiences can function via epigenetic mechanisms to turn on and off various genes. And, remarkably, evidence is growing that some of those epigenetic codes are stored in a way that can be passed down through the generations. If so, then then the essence of Larmarck’s version of evolution may have far more elements of truth to it than is currently taught.
The most recent journal of Nature Neuroscience (December 2013), provides some powerful--what I found to be shocking--evidence of epigenetic transmission of…get this…LEARNING!
Researchers Brian Dias and Kerry Ressler of Emory University School of Medicine trained male mice to fear a specific chemical smell. They then examined the mice’s offspring and found they demonstrated the fear response to the same smell. The only way this information could have been transmitted, based on the design of the study, was via epigenetic changes to the sperm. Thus, the fear-based learning resulted in epigenetic changes in the sperm of the origin mouse which were passed down to the subsequent generations of mice (at least the next two). The researchers also showed that the brains of the offspring mice showed similar configurations to the mice that actually experienced the fear. And they showed that the fear response was specific to the original chemical and not triggered by other smells.
From a psychological perspective, this is a HUGE finding. For starters, the idea of inter-generational trauma becomes much more complicated with an almost infinite number of possible causal pathways. At a more abstract level, the possibilities become truly remarkable—things like generational psychological legacies and notions such as Carl Jung’s collective unconscious archetypes, which might have seemed farfetched in the past, become more scientifically plausible.
From a biological perspective, it adds to what appears to be a growing body of findings that are pointing to an emerging revolution in our understanding of biology (see here). It seems we may be on the brink of a major paradigm shift that will involve fundamentally re-writing the essence of the modern synthesis.