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This came up in a talk with a friend. I wanted to clear this doubt. I've read about it before and did again after her remark (my thoughts didn't change: her concept is Lamarck's, not Darwin's), but wanted to clarify.

Regarding Evolution, nothing, absolutely nothing, that a person does to herself in life can be genetically inherited. It does not matter how much this person drinks, the changes they do to their body, how dark their skin gets over life etc. Such changes can not be transmitted to their offspring in any way, correct?

*Summary:*Is the assertion "You can not change in life what will be genetically inherited in any possible way" true?

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Yes, short of drinking mutagens every day to deliberately induce mutations –  Rory M Feb 2 '12 at 8:40

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up vote 15 down vote accepted

The assertion "You cannot change in life what will be genetically inherited in any possible way" is true, as you cannot (healthily) change the DNA in your germ cells.

However, the assertion "You cannot change in life what will be inherited in any possible way" is wrong, because of epigenetics. Parts of your DNA are marked (in different ways), and this can be inherited and have an effect. E.g. the only causal difference between these two mice is the diet of their mothers:

Two mice of same genotype but different phenotype

Image source and a further explanation: Nutrition and the epigenome.

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–1, the paper didn’t actually provide evidence of epigenetic inheritance in any meaningful sense of the word, as is the more general conclusion: so far as we know, there is no single naturally occurring case of passing on of acquired traits. This isn’t unthinkable (see Prader-Willi syndrome), but remains yet to be demonstrated. I’ve written my take on the subject on Skeptics.SE: skeptics.stackexchange.com/a/7338/82 –  Konrad Rudolph Feb 6 '12 at 23:42

Is the assertion "You can not change in life what will be genetically inherited in any possible way" true? No. Does not seems the case, as other people already replied.

Here, I just want to point to two recent research articles showing evidence against your assertion.

The first, published in Cell in 2010, is from Dr Oliver Rando, and suggests that you are what your father ate, too. The second, published in Nature in 2011, is from Dr Anne Brunet, and argues that worms can inherit a 'memory of longevity' from long-lived parents.

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That last paragraph is completely unnecessary. Anyone who knows what is going on would know this. –  bobthejoe Feb 3 '12 at 20:58
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The purpose of peer review is not to detect fraud, so the peer review process did not fail 24 times for the same researcher. It's just that a researcher falsified his results. Unfortunately in science, as in all things, people can be deceiving. I don't think it's a reason to be any more skeptical about scientific papers than about anything else, and indeed scientific papers have other characteristics that make them, generally, the most reliable source of information we have. –  Richard Smith Jun 28 '12 at 1:03

Infections by a retro-virus (such as HIV) can, at least in principle, be inherited.
These viruses integrate their genetic code into the host's DNA, and these changes pass to next generations as the cells split. So if a germ cell is infected, all the cells in the child would be.

The question is whether there's a retro-virus that infects germ cells. I don't think HIV does (it can certainly pass from mother to child, but as a "normal" infection, not through the DNA).

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In general, Darwin's theory has been supported over and over again by experiments - our modern understanding of evolution is fundamentally what Darwin suggested. However, apart from appreciating many more details than Darwin ever could have, we also now know that Lamarck may not have been so crazy as he was later portrayed.

Inheritance in the Darwinian sense involves the digital information of DNA, i.e the sequence of bases. But we also know that DNA can be altered structurally - i.e. in the way it folds, or whether bases are methylated - and that these structural alterations can affect the expression of genes. In some cases, these epigenetic modifications can be trans-generational; they can be passed on to offspring.

Here are the mechanisms that I know of (perhaps others can expand on this):

  • X-chromosome inactivation (XCI): this is when one of two copies of the X-chromosome in females is completely inactivated by being packed into heterochromatin, preventing the DNA from being transcribed. Which chromosome (the maternal or paternal) is deactivated initially is random, but the decision can be inherited by all daughter cells. Skewed x-inactivation is when a cell very early in the cell line passes on its XCI decision, and can result in a particular phenotype being activated in a whole organ or tissue (such as patches in tortoiseshell cats). It has been shown that in mice and in humans, the somatic cells can sometimes have their XCI decision influenced by the mother, and that this can lead to early skewing of the XCI in the offspring, thereby passing on a decision about which alleles are present without affecting the DNA sequence.
  • Parental imprinting: in this case, individual alleles derived from one parent are preferentially activated or deactivated by methylation or histone modification. This change is passed on to the zygote, and alters expression in the offspring. Several human heritable diseases are associated with this kind of modification, such as Prader-Willi Syndrome.
  • Paramutation: first discovered in maize, this is when the presence of one allele in a genome can affect another allele in a heritable way. I.e. if allele A is present in the same genome as allele B for a single generation, allele A is permanently inactivated so that if you breed out allele B, allele A will not be active in the offspring.

Finally, there is also a phenomenon called structural inheritance, whereby a structural feature of an organism is inherited in a non-genetic way. There is less written about this, so the mechanism is not entirely clear as far as I know, but an example is that the 'handedness' of the spiral pattern on the shell of a protozoan Tetrahymena is inherited without any genetic change (Nelsen et al., 1989).

References:

Nelsen, E.M., Frankel, J. & Jenkins, L.M. (1989) Non-genic inheritance of cellular handedness. Development (Cambridge, England). 105 (3), 447–456.

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