Neo-Darwinism and Lamarkism


(Albert Leo) #1

In a previous post I cited de Duve’s book, “Genetics of Original Sin…” which in Chpt 8 discusses how something like “Lamarkian inheritance” can occur through epigenetic changes to the developing brains of both animals and humans. A recent paper in Science (3/23/18; V.359; p.1330) presents the results of experiments along these lines. The following is a quote from the summary:

“The relationship between genes and the environment on the brain and how they affect behavior has been a long-standing issue. Can the genome of the individual brain cells be changed by environmental factors? If so, which types of genetic changes can result?What is the basis of this genetic diversity? What are the physiological implications? Bedrosian et al explore one possibility for how neuronal genomes can exhibit plasticity in response to environmental factors during early life, providing integrative evidence for the effect of early maternal care on the genomes of neurons.”

I understood that some folks in the 19th century hated to see Lamarkism replaced by Darwinism, because they felt that with the latter view the “ills of human nature” were cast in stone according to the ‘genetic hand’ you were dealt with at birth. This article in Science seems to indicate that parents can use ‘brain plasticity’ to steer the function of their children’s brains to operate in a more productive manner than they otherwise would have. Of course the article makes no claim that any such improvement can be passed on through the children’s genes (i.e. true Lamarkism), but it does give us hope that our human fate is not completely a “throw of the dice”.

Again, I highly recommend de Duve’s book, and I would like to hear the views that BioLogos resident experts have on this subject.
Al Leo


#2

The only problem is that we don’t use brain cells to reproduce (not meant as a joke, but still had to laugh). Any epigenetic changes that occur in brain cells are not passed on to offspring. In Lamarckian inheritance, those changes are passed on.

If anything, we are born with a certain amount of phenotypic plasticity. That is, we are born with the ability to change our bodies in response to environmental cues. We tan in the summer and increase muscle mass in response exercise, as a couple of examples. We inherit the ability to produce these changes, but we don’t inherit the changes that occurred in our parents. If a mother gets a great tan in the summer she doesn’t give birth to a tanned baby, as one example.


#3

Well, we do have some studies indicating that propensity to obesity can be epigenetically inherited, although we don’t reproduce with our fat cells, so I don’t completely dismiss the possibility that the same thing could hold true for muscular mass gain or even intelligence to some degree. Of course, those epigenetic changes would have to be passed to our germ cells in some way for that to happen.


(Stephen Matheson) #4

I haven’t seen your post or the de Duve book, but the Science paper is not about Lamarckian inheritance. It is very, very interesting but it is about how early life experience can alter the genomes of brain cells. The group had previously shown that mobile genetic elements are unusually active in neurons during development (technically, they are active in the cells that make neurons). This means that neurons in the mammalian brain (at least) are thus genetically diverse. The process has been linked to diseases/conditions such as schizophrenia (link below).

But Lamarckian inheritance, by definition, is between generations. And as @T_aquaticus has already pointed out, brain cells don’t make gametes.

http://www.cell.com/neuron/fulltext/S0896-6273(13)01005-2


(Matthew Pevarnik) #5

Another recent paper along these lines is also the development of Cichlid jaws… but this epigenetic variation again is not being passed down by any means in a Lamarkian sense:


(Stephen Matheson) #6

Definitely cool. The L1 story is different and more dramatic, because the changes are at the genomic level. So-called ‘epigenetic’ effects like the fish jaw story need not (and do not) affect the genome (i.e., they don’t change the DNA sequence). Though I haven’t read the cichlid paper.


#7

I have heard of those studies in passing (e.g. inherited obesity), but have never looked into them in depth. At first blush, there could be other factors outside of inherited methylation or histone packaging patterns in play, but more reading is definitely required.


#8

Yeah, I’ve heard from them in passing as well. I’ve done some short research into that and it is basically what you said, although we do have some evidence for transgenerational epigenetic inheritance, it is still controversial because of potential confounding factors in mammals. In plants however, we do seem to have a much stronger case for that type of inheritance actually happening.


EDIT: Of course, that is not to say that this is what is happening in the studies of the first post, but it coud happen in other contexts.


#9

After skimming through your references and one I found, there are some serious hurdles to Lamarkian-like inheritance in mammals through inherited epigenetic markers (i.e. methylation patterns). There appears to be two rounds of demethylation early in mammalian development that demethylates almost all of the paternal DNA, and then a second round in the first few cell divisions that nearly demethylates the entire genome. It would appear that mammalian development relies more heavily on methylation during development, so it has to wipe out any previous epigenetic markers so it can start fresh with a cell that can become all other types of tissues.

That isn’t to say that some markers can make it through, or that other factors like RNA molecules can’t play a role, but it doesn’t look like an all-encompassing inheritance system that plays a large role in shaping offspring. At best it might tweak a few things here and there, at least in mammals.


#10

Yeah, I’m rather skeptic about how much it plays a role in mammals as well, but Lamarkian-like inheritance as a whole seems to be a thing at least in some organisms like plants, and even minor tweaks would be interesting in mammals. They do seem to have some really interesting working hypothesis on how these markers can make through which are worth investigating, though.


(system) #11

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