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The “better explanations” are called epigenetics. Environmental factors can cause genes to be turned off or on and that in turn can be passed to children. So th

The “better explanations” are called epigenetics. Environmental factors can cause genes to be turned off or on and that in turn can be passed to children. So the environment doesn’t effect your DNA (Lamarckian evolution) but it can still cause your offspring to act differently.

monocasa 8y ago
Translating a bit for people coming at this from a CS background: epigenetics is the recognition that cell division (eiher mitosis or meiosis) is way more like fork(2) than exec(2). There's tons of current mutable state maintained across the division in addition to the more or less fixed executable (DNA).
- losteric 8y ago
  Epigenetics is fascinating because methylation is a basic read/write layer on top of static DNA - changes can appear in a living organism and propogate to offspring. > Even short-term substance abuse can produce long-lasting epigenetic changes in the brain of rodents, via DNA methylation and histone modification. https://en.m.wikipedia.org/wiki/Behavioral_epigenetics https://en.m.wikipedia.org/wiki/Behavioral_epigenetics
  - deleted 8y ago
    [deleted]
darkpuma 8y ago
> Environmental factors can cause genes to be turned off or on The principle here is straight forward, but it's not clear to me that anybody has actually demonstrated a clear 'signal' in the process. In other words there is evidence that stress caused by fire trauma can change the way genes are expressed in an individual, and I believe there is evidence that stress from trauma can impact gene expression at the process of genetic recombination. However I've not seen any evidence that, for instance, stress caused by fire will induce any sort of specifically fire related gene expression in offspring. Would an orphan who never knew their parents have an elevated fear of fire if both their parents had survived a severely traumatic experience with fire? To my knowledge, that's still purely speculative. The closest I've seen is the suggestion that offspring of famine survivors may have an epigentic change that makes them gain weight: >The field of epigenetics gained momentum about a decade ago, when scientists reported that children who were exposed in the womb to the Dutch Hunger Winter, a period of famine toward the end of World War II, carried a particular chemical mark, or epigenetic signature, on one of their genes. The researchers later linked that finding to differences in the children’s health later in life, including higher-than-average body mass. But that leaves open many questions. What other epigentic changes did these people have that seem unrelated to food/weight? And how many people who suffered from trauma unrelated to food availability have changes that effect weight gain?
- iguy 8y ago
  The Dutch children are an odd example here, because they themselves experienced hunger in the womb. That their bodies remember this isn't surprising at all. The markers through which this is remembered are sometimes called epigenetic, the word seems to be a little fuzzy... I guess there is a small step between individual cells having persistent changes, and daughter cells in the same individual inheriting such changes. (But again unsurprising: the embryo needs to mark some cells as future-leg-material when it's only a few hundred cells, and their millions of actual-leg-cell descendants remember.) The big and controversial step is to writing such changes into the germ-line, so that offspring of the individual cary such a memory. And my understanding is like yours, that there's some evidence for crude things (like massively stressed / starved mice having offspring who are calibrated a bit differently) but not really anything solid for the sort of finer changes we like to speculate about in humans. It's not impossible, and it need not be un-Darwinian: your genes care more about how many grandkids you have than how many kids, and if pre-adjusting your kids to the environment is advantageous, then they certainly have the motive to do it. And there are corners of biology in which you could hide a mechanism to do this (just a little bit) where we would not yet have seen it. But a lot of the tantalising studies seem to underplay ordinary inheritance. For example, lots of abused children, sadly, have a 1st-degree relative who abuses children. Some of whatever is wrong with the abuser may also be wrong with the victim (through no fault of anyone's!) and this may show up on all sorts of measures. Removing such things from your data is going to be super-hard, and if you succeed, you are more likely to get a boring paper.
  - darkpuma 8y ago
    >"The Dutch children are an odd example here, because they themselves experienced hunger in the womb. That their bodies remember this isn't surprising at all." Good point, there's an ocean of difference between experiencing hunger in the womb, and being well nourished in a womb belonging to a woman who was once malnourished. I don't have that study available to me at the moment to check, but I wonder what they say about children born from those same mothers years after the famine was over. Surely they looked at that too, since if the same signal was present that would certainly enhance their findings. If the study doesn't mention those later children at all, that would suggest to me they're guilty of p-hacking.

monocasa 8y ago

Translating a bit for people coming at this from a CS background: epigenetics is the recognition that cell division (eiher mitosis or meiosis) is way more like fork(2) than exec(2). There's tons of current mutable state maintained across the division in addition to the more or less fixed executable (DNA).

losteric 8y ago
Epigenetics is fascinating because methylation is a basic read/write layer on top of static DNA - changes can appear in a living organism and propogate to offspring. > Even short-term substance abuse can produce long-lasting epigenetic changes in the brain of rodents, via DNA methylation and histone modification. https://en.m.wikipedia.org/wiki/Behavioral_epigenetics https://en.m.wikipedia.org/wiki/Behavioral_epigenetics
- deleted 8y ago
  [deleted]

darkpuma 8y ago

> Environmental factors can cause genes to be turned off or on The principle here is straight forward, but it's not clear to me that anybody has actually demonstrated a clear 'signal' in the process. In other words there is evidence that stress caused by fire trauma can change the way genes are expressed in an individual, and I believe there is evidence that stress from trauma can impact gene expression at the process of genetic recombination. However I've not seen any evidence that, for instance, stress caused by fire will induce any sort of specifically fire related gene expression in offspring. Would an orphan who never knew their parents have an elevated fear of fire if both their parents had survived a severely traumatic experience with fire? To my knowledge, that's still purely speculative. The closest I've seen is the suggestion that offspring of famine survivors may have an epigentic change that makes them gain weight: >The field of epigenetics gained momentum about a decade ago, when scientists reported that children who were exposed in the womb to the Dutch Hunger Winter, a period of famine toward the end of World War II, carried a particular chemical mark, or epigenetic signature, on one of their genes. The researchers later linked that finding to differences in the children’s health later in life, including higher-than-average body mass. But that leaves open many questions. What other epigentic changes did these people have that seem unrelated to food/weight? And how many people who suffered from trauma unrelated to food availability have changes that effect weight gain?

iguy 8y ago
The Dutch children are an odd example here, because they themselves experienced hunger in the womb. That their bodies remember this isn't surprising at all. The markers through which this is remembered are sometimes called epigenetic, the word seems to be a little fuzzy... I guess there is a small step between individual cells having persistent changes, and daughter cells in the same individual inheriting such changes. (But again unsurprising: the embryo needs to mark some cells as future-leg-material when it's only a few hundred cells, and their millions of actual-leg-cell descendants remember.) The big and controversial step is to writing such changes into the germ-line, so that offspring of the individual cary such a memory. And my understanding is like yours, that there's some evidence for crude things (like massively stressed / starved mice having offspring who are calibrated a bit differently) but not really anything solid for the sort of finer changes we like to speculate about in humans. It's not impossible, and it need not be un-Darwinian: your genes care more about how many grandkids you have than how many kids, and if pre-adjusting your kids to the environment is advantageous, then they certainly have the motive to do it. And there are corners of biology in which you could hide a mechanism to do this (just a little bit) where we would not yet have seen it. But a lot of the tantalising studies seem to underplay ordinary inheritance. For example, lots of abused children, sadly, have a 1st-degree relative who abuses children. Some of whatever is wrong with the abuser may also be wrong with the victim (through no fault of anyone's!) and this may show up on all sorts of measures. Removing such things from your data is going to be super-hard, and if you succeed, you are more likely to get a boring paper.
- darkpuma 8y ago
  >"The Dutch children are an odd example here, because they themselves experienced hunger in the womb. That their bodies remember this isn't surprising at all." Good point, there's an ocean of difference between experiencing hunger in the womb, and being well nourished in a womb belonging to a woman who was once malnourished. I don't have that study available to me at the moment to check, but I wonder what they say about children born from those same mothers years after the famine was over. Surely they looked at that too, since if the same signal was present that would certainly enhance their findings. If the study doesn't mention those later children at all, that would suggest to me they're guilty of p-hacking.