Epigenetics: Your Behavior Affects Your Children’s DNA

The diversity of life is astonishing. As of now, there are over 2 million known species, many of which are so bizarre they sound as if they came out of a science fiction novel. From extremophile bacteria that can live in near boiling water to algae that can live in the frozen landscape of Antarctica; from the mighty blue whale to the plankton they eat; from translucent fish to blind mole rats–the world is full of creatures both strange and beautiful. And there may be up to 30 million more species still undiscovered.

Scientific explanations for where this wonderful diversity comes from began in earnest in 1809 with Jean-Baptiste Lamarck and continued with great minds such as Mendel, Darwin, Kossel, Avery, Chargaff, Watson, Crick, among many others. Each of these helped us gain a new understanding of how “one species does change into another,” as Darwin had scribbled in his notebooks shortly after his famous voyage on the HMS Beagle.

Today, evolutionary biologists continue to push forward, most notably with the addition of the new field of epigenetics, which, quite strangely, has brought us full circle back to Lamark’s thought-to-be incorrect ideas.

Lamarck vs. Darwin

Lamarck was well known French academic, best remembered for creating the first concrete hypotheses of evolution. He proposed that an when organism responds to its environment, it develops new characteristics, which are passed to it’s offspring. For example, a giraffe’s long neck is the result of its ancestors reaching for leaves. Another example is if a person exercises his arms, then his children will naturally have stronger arms. At the time and for many decades after, this seemed to explain why animals had the specific traits needed to survive in unique environments.

However, Darwin proposed the theory of evolution by natural selection in 1859 in his book “The Origin of Species.” The simple explanation of his idea is that an organism’s characteristics help determine its chances of survival and successfully procreating. Those organisms with characteristics more suitable to the environment are more likely to survive and have more offspring, thus passing on the beneficial characteristics. Over time, these characteristics will be more present in the population’s gene pool. Over long periods of time and changes to the environment, a population’s gene pool can undergo radical changes to make it a different species. Since life appeared on Earth some 4 billion years ago, natural selection has transformed the first microbes into the diverse living world we see today. 

A decade after Darwin proposed his idea, DNA was discovered by Friedrich Miescher, but it wasn’t until many decades later that scientists realized it was the means of information transfer between generations. That is, natural selection doesn’t just select for characteristics, it selects for the DNA sequences that encode the characteristics, known as genes. These genes also mutate due to transcription errors, damage, etc., producing new characteristics, some beneficial, some harmful. Therefore, random mutations can lead to a population’s gene pool changing rather quickly.

Darwin’s theory of evolution by natural selection still stands as solid science, although epigenetics has shown there is an extra layer of complexity.

Epigenetics

Epigenetics means above, in addition to, or outside of genetics. Beginning in the early 2000s, scientists began to gather evidence for unexplained trans-generational inheritance. For example, in this 2005 Swedish study the researchers found “A nutrition-linked mechanism through the male line seems to have influenced the risk for cardiovascular and diabetes mellitus mortality.” The study looked at men that lived through a famine before puberty and discovered that this had an effect on the health of future generations. Likewise, this study found that men who started smoking before the age of 11 had greater chances of producing boys with above average weight. Clearly, the behavior of the parents was affecting the children’s DNA in a way Darwin couldn’t explain, as natural selection was not at work.

It turns out an organism’s characteristics come from both DNA and how DNA is expressed. Every cell in the organism contains the same copy of DNA, but the cells differentiate based on which DNA sequences are expressed. Therefore, your liver cells differ from your heart cells simply by turning on different DNA sequences. This happens due to the presence of specific chemical tags, which affect the histones. Histones are particular proteins that help package DNA. Histones and the production of chemicals that affect them can be permanently changed by a variety of factors, including diet, surrounding environment, etc.

Changes in histones and relevant chemicals can be passed to the next generation. Because of this, your children’s DNA is expressed differently, depending on what happened to you. If you had a poor diet or smoked three packs of cigarettes a day, then your children will also bear the burden, as they will have inherited your altered histones and the chemicals that affect them.

Therefore, you are making decisions today that will affect future generations, just as you are affected by the myriad of decisions made by your ancestors.

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