Science & Faith
5/25/12 at 05:35 PM 2 Comments

Rethinking Nongenetic Inheritance and How this Relates to Evolutionary Theory

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Human Sperm

The June 2012 issue of the journal Trends in Ecology and Evolution contains an important review of research on biological inheritance. This article, "Rethinking heredity, again" (a free download), shows that the pioneers of the evolutionary neo-Darwinian “Modern Synthesis” since the 1930s have been prematurely dismissive of what is called “soft” inheritance. This allegedly discredited sort of inheritance includes the idea that organisms can pass on traits that they acquire during their lifetime. Although much of this perspective, associated with the late 18th-century scientist Lamarck, has not been well supported by evidence, a broader category of inheritance factors beyond “hard” genetic inheritance has recently come to light, and is know as “nongenetic inheritance.” In short, what you inherited from mom and dad includes both genes, and more. Together, all these factors determine the physical traits you exhibit.

The new biological inheritance literature review by R. Bonduriansky promises this:

In this paper, I trace changes over the past century in the core issues at stake in the inheritance debate – the politically charged scientific controversy over the nature of heredity – and show that the concept of soft inheritance that was rejected by 20th-century genetics differs fundamentally from the one [i.e., nongenetic inheritance] at the center of current debate.

Bonduriansky also writes:

However, the empirical evidence now points to the existence of a variety of inheritance mechanisms (collectively called ‘nongenetic inheritance’) that operate alongside Mendelian inheritance and allow for the inheritance of acquired traits.

Many of the interesting examples come from epigenetics, as Bonduriansky explains:

Furthermore, experiments on diverse animals, plants and unicellular organisms showed that parental environment, phenotype or genotype, sometimes affects offspring phenotype, a phenomenon called ‘parental effects’ or ‘indirect genetic effects’.

In other words, the biological traits of parents and the physical environment in which the parents live work together, with inherited genes, to determine how the offspring look (offspring phenotype). But how do the nongenetic inheritance mechanisms work? Bonduriansky continues:

Recent discoveries in molecular and cell biology have revealed novel mechanisms, such as transgenerational epigenetic inheritance, that could account for a variety of parental effects. Empirical studies are now providing evidence that parental effects can be mediated by a range of substances in the gametes [eggs and sperm in the case of animals], and also parental glandular and other somatic donations, behavior and environment, and can affect a range of offspring traits.

So it not just the genes on the DNA in the sex cells (eggs and sperm), but also other substances carried within the sex cells that determine offspring traits. Wild! He also notes:

Although it was long thought that maternal effects [i.e., nongenetic factors from the mother] were far more common than paternal effects [i.e., nongenetic factors from the father] because of the greater opportunity for maternal influence on offspring development, this view is being challenged by the increasing number of examples of paternal effects.

So what implications does this have for the debate over Darwinian evolution today? I will let my colleague Jonathan Wells of Discovery Institute explain that part of this amazing story. He does so here. I designed my introduction to help non-biologists better grasp what Wells is saying.

PS: Don’t miss Wells’ conclusion:

This would be an example of how a preoccupation with evolutionary theory can divert attention away from some of the most interesting (and potentially most revolutionary) aspects of heredity and development.

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