"Early in life effects and heredity: reconciling neo-Darwinism with neo-Lamarckism under the banner of the inclusive evolutionary synthesis" -review

The article "Early in life effects and heredity: reconciling neo-Darwinism with neo-Lamarckism under the banner of the inclusive evolutionary synthesis" by Étienne Danchin (2019) argues that the traditional view of inheritance, which is based on the gene-centered view of evolution, is incomplete. The author proposes an inclusive evolutionary synthesis that takes into account the role of non-genetic factors in inheritance, such as epigenetics.

The traditional view of inheritance holds that the only source of heredity is the DNA sequence. This view is based on the work of August Weismann, who proposed the germ plasm theory in the late 19th century. The germ plasm theory states that the germline, which is the cells that give rise to gametes, is separate from the soma, which is the rest of the body. This means that changes to the soma cannot be inherited by the next generation.

However, recent research has shown that epigenetics, which is the study of changes in gene expression that are not caused by changes in the DNA sequence, can have a long-lasting impact on an organism. Epigenetic changes can be caused by environmental factors, such as diet, stress, and exposure to toxins. These changes can be inherited by the next generation, even if the DNA sequence itself is not changed.

The author of the article argues that the traditional view of inheritance is too narrow and that it does not take into account the role of epigenetics. The author proposes an inclusive evolutionary synthesis that takes into account both genetic and non-genetic factors in inheritance. This synthesis would allow us to better understand the role of early life experiences in shaping the phenotype of an organism, and it would also allow us to develop new interventions to improve health and well-being.

The article "Early in life effects and heredity: reconciling neo-Darwinism with neo-Lamarckism under the banner of the inclusive evolutionary synthesis" is an important contribution to the field of evolutionary biology. The author's argument that the traditional view of inheritance is incomplete is well-supported by the evidence. The inclusive evolutionary synthesis that the author proposes is a promising new framework for understanding the role of early life experiences in shaping the phenotype of an organism.

Here are some other articles that discuss the role of non-genetic factors in inheritance:

• "Epigenetics: A Bridge Between Nature and Nurture" by Matt Ridley (2006)

• "The Epigenome and Its Role in Human Disease" by Michael J. Meaney (2008)

• "Epigenetics and the Environment" by Bruce S. McEwen (2012)

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Article snippets:

Recent discoveries show that early in life effects often have long-lasting influences, sometimes even spanning several generations

Such intergenerational effects of early life events appear not easily reconcilable with strict genetic inheritance.

The fantastic technological developments of molecular biology since the 1990s, although entirely placed within this view, eventually led to the finding that the accounting of the sole genetic variation does not explain inheritance in all its complexity

The ubiquity of this discrepancy on its own suggests that a genes-only view of heredity may be far from sufficient to explain trait inheritance.

Such intergenerational effects of early life challenges are not easily reconcilable with strict genetic inheritance, and raise many, sometimes provocative, questions such as ‘when does early life start?’ or ‘is there a somewhat Lamarckian component to acknowledge in evolution?’

A central aspect of the current research programme calling for an extended [20,22,23] or inclusive [5,15,24] synthesis is that all examples of transmission of acquired adaptations largely lead us to reconsider concepts of heredity and call for the crystallization of a much broader concept of inheritance

Inclusive Evolutionary Synthesis: The extension of the Modern Synthesis that includes all components of inheritance and their interactions. Its ambition is to incorporate any known forms of parent–offspring resemblance, including epigenetic, ecological and cultural inheritance, parental effects of all sorts, as well as the inheritance of microbiota or the effects of any molecular memory system such as, for instance, in prions.

Non-genetic inheritance: Mechanisms of heredity that do not rest on variation in the DNA sequence

To him, and some of his successors who were to be called the neo-Lamarckians, inheritance was soft, pliable

The stability of the DNA sequence also seems to justify the concept of hard inheritance at work in evolutionary theory

Among others, a challenge came from accruing evidence for the existence of non-genetic (non-DNA-sequence-based) forms of inheritance, to which we turn now.

the widely accepted concept of the Weismann barrier between somatic cells and germ cells in animals needs to be revisited as not only is the germline not isolated from the external world, but there are also specific and sophisticated mechanisms that seem to modify the germline in response to environmental change.

Such mechanisms have a Lamarckian flavour, strongly at odds with the Modern Synthesis' view,

Concerning transgenerational epigenetic inheritance, the stability of DNA methylation patterns across generations is only estimated for CpG pairs where it varies from 10−2 [86] to 10−4 per CpG pair per generation

This strongly suggests that organisms should have evolved ways of transferring recently acquired information about current environment to their offspring in a possibly relatively persistent manner

Such intergenerational transfers of accommodations to recent past environments are likely to significantly influence the way genes are expressed in interaction with the current environment in descendant organisms

Thus, RNA emerges as a major, and overlooked, inheritance molecule, complementing and interacting with the DNA.

Epigenetic marks are considered mutagenic under certain circumstances [132,133], implying that they can affect the stability of physically linked more stable variants (the DNA sequence). They may thus play the role of a hub towards more stable information encoding in a form of Epigenetically-Facilitated Mutational Assimilation (EMFA, figure 5, [19]), somehow enabling the genetic and non-genetic systems to ‘talk’ to each other