Interesting bit of science that could fuel a SF story?

[Ensign Shah]

http://www.theguardian.com/science/...ors-finds-trauma-passed-on-to-childrens-genes

Came across this and found it *raises left eyebrow in a Vulcan manner* intriguing.

Research, that life experience can affect the genes of subsequent generations.

 

[Stephen Palmer]

This book is well worth a read.

 

[Dave]

“The gene changes in the children could only be attributed to Holocaust exposure in the parents,” said Yehuda.

Without reading the entire article or book, can you tell me why they make this claim? That is the crux of the whole hypothesis and I think that would be very difficult to prove given that European Jewry has suffered a much longer exposure to such experiences during the Pogroms. It is quite a huge claim to make to say that gene changes can take place in a single generation. That was Lamark's Theory of Inheritance of Acquired Characteristics which was overtaken by Darwin's Theory of Natural Selection. You probably were taught about it in school, where Lamark thought Giraffes stretched their necks up into the trees and as a result the baby Giraffes had longer necks.

 

[Ray McCarthy]

My scepticism alert has blown its LEDs.
Certain kinds of environment can affect development, and maybe even genetics (huge increase or decrease in sunlight due to mother/grandmother changing country results in lighter or darker offspring at birth) but this sounds like dodgy science.

 

[Ursa major]

I seem to recall this being an issue in Sweden**, of all places. It seemed that where one generation had suffered some sort of deprivation, it affected (in ways that I can't remember at all) not the following generation but the one after that.

Googling "sweden deprivation epigenetics third generation" brought up this pdf***. This isn't what I was referring to -- the paper was published as recently as February 2014 and deals with subjects in Germany, not Sweden. (I haven't done more than glance at the paper' abstract, as I have to mow the lawn before it starts raining....)


** - Sweden was, I think, a relatively poor country in the first half of the twentieth century.

*** - With the catchy title A Validation Study of Transgenerational Effects of Childhood Conditions on the Third Generation Offspring’s Economic and Health Outcomes Potentially Driven by Epigenetic Imprinting.

 

[Venusian Broon]

It is quite a huge claim to make to say that gene changes can take place in a single generation. That was Lamark's Theory of Inheritance of Acquired Characteristics which was overtaken by Darwin's Theory of Natural Selection. You probably were taught about it in school, where Lamark thought Giraffes stretched their necks up into the trees and as a result the baby Giraffes had longer necks.

They are not claiming this - epigenetic is about the environment (and seems to be have been found most prominently when humans are in stressful environments) manipulating the genome to provide a "stably heritable phenotype resulting from changes in a chromosome without alterations in the DNA sequence" (see https://en.wikipedia.org/wiki/Epigenetics#Contemporary_usage). It is Lamarkism to a degree. However it does not impact the actual genome. Effectively it is the rest of the cell activating certain genes that would normally be dormant - at least that is how I'm imagining it.

But then there are all sorts of shenanigans that are involved in DNA & development - for example there are some very important genes that we have discovered were actually very recently spliced into our genome by viruses, something that we thought only happened to bacteria, a sort of uber-mutation I suppose.

 

[Ray McCarthy]

manipulating the genome to provide a "stably heritable phenotype resulting from changes in a chromosome without alterations in the DNA sequence"

That could be what the sunlight on parent vs Melanin of child is related to?

 

[Venusian Broon]

That could be what the sunlight on parent vs Melanin of child is related to?

To be frank I don't know. I'd imagine the long term effects ,i.e. many generations, are largely Darwinian on skin colour given the negative impact of skin cancer on those with light skin. But, who knows what happens in the short term. We need a bio-geneticist working in the field to tell us! (Unfortunately most of the geneticist I know worked with plants. Very interesting but not illuminating in this case )

 

[Ray McCarthy]

I'd imagine the long term effects ,i.e. many generations, are largely Darwinian on skin colour

However the skin colour change (in pigmentation at birth) is as soon as next generation for parents that moved. That has surprised scientists. But I don't know if there was a genetic change. The article didn't mention any genetic tests. It's more marked for say people from Poland or Russia to Israel than Africans to much more Northern places. Very dark people recently moved to say UK from tropical or Horn of Africa can easily be very short of vitamin D. But their children are not so badly affected and not so darkly pigmented.

Some paler "African-Americans" might simply be paler and not purely due to European interbreeding.

 

[Ursa major]

I can't help feeling that some of the effect is simply the skin reacting to the change in the light levels, i.e. naturally paler people who move to (or are born in) sunnier climes getting, in effect, tans, so we're comparing two different things: the skin colour as determined by 1) genetics and 2) average sunlight levels.

Note that the effect of sunlight -- or, rather, exposure to it -- is recorded in Ancient Egyptian paintings, where those who toiled in the fields were shown with much darker skins than those who didn't. (And isn't this -- that skin colour is seen as an indicator of social status -- what partly lies behind the skin lightening industry in south Asia?)

 

[hardsciencefanagain]

it doesn't sit well with the stochastic nature of transcriptional regulation.

 

[Ray McCarthy]

the effect of sunlight ... I can't help feeling that some of the effect is simply the skin reacting to the change in the light levels

Yes, of course it's a reaction to sunlight. But the larger effect on new born (who has not yet been outside) than on the adult (who might have arrived 10 years ago) is interesting.

Ancient Egyptian paintings, where those who toiled in the fields were shown with much darker skins than those who didn't.

The "older" Egyptian people were not like modern Arabs. The ordinary folk were more like Ethiopians. The Rulers as well as being indoors may have been related to people in the Levant, Mesopotamia, Arabia etc. Cleopatra (not so ancient) was of course descended from Greek rulers of Egypt from time of Alexander the Great.

 

[Ursa major]

The "older" Egyptian people were not like modern Arabs.

Of course not: they were (ancient) Egyptians, not Arabs, not Ethiopians.

Just a question.... Why would ancient Egyptians (or whatever social standing**) look like Ethiopians, of all people? First of all, Ethiopia is a long way from Egypt (farther away than the nearest bits of Arabia). Surely ancient Egyptians would be most closely related to those living nearby, i.e. people in the Levant, north Africa (such as those we call the Berbers***) and Nubia, not to mention those living in what is now the Sahara Desert, when it wasn't quite so dry. Second, just about all of ancient Egypt is situated north of the tropics (Abu Simbel and places south of it being exceptions). So, for example, Addis Ababa is as far south of Cairo (by 21 degrees of latitude) as Cairo is south of London.


** - Other than slaves, all ancient Egyptians were, in theory, equal before the law, which seems to suggest that (other than the times when pharaohs weren't Egyptians at all) the country was not divided by ethnicity.

*** - The Ancient Egyptian language is, apparently (and unsurprisingly), related to both Berber and Semitic languages.

 

[Ray McCarthy]

Ethiopia is a long way from Egypt

I don't know. Something to do with people travelling up / down the fertile Nile and not across deserts?
It's probably not modern Ethiopia, but some upper Nile region in Horn of Africa near Modern Ethiopia

I can't remember where I read that the oldest Egyptians were related to Ethiopians. It wasn't Wikipedia. A book ...

Of course some older books (e.g. Victorian) have very strange ideas about the past. It seems that over 100 years ago people thought Irish Round Towers and places like Newgrange were built by same people, when there is actually nearly 3,000 years difference. Sometimes Wikipedia is more reliable than "random book". In the middle Ages, people in Europe confused Horn of Africa with India (there were Ethiopian Christians that visited Rome)*

related to both Berber and Semitic languages

So is Proto-Gaelic, Irish, Sandskrit/Ancient Indian, Hittite etc. The longer ago you go in Middle East, North Africa, Horn Of Africa, India etc the fewer languages there are?

[* There was a R4 program recently trying to unravel Prester John and related Mediaeval reports of India and Horn of Africa Christians. The Europeans seem to have got thoroughly confused by the Mongols, who were not interested in "taking sides" between the Christians and Moslems as they didn't care what religion people had as long as Mongols ruled.]

Prester John had been considered the ruler of India since the legend's beginnings, but "India" was a vague concept to the Europeans. Writers often spoke of the "Three Indias", and lacking any real knowledge of the Indian Ocean, they sometimes considered Ethiopia one of the three. Westerners knew that Ethiopia was a powerful Christian nation, but contact had been sporadic since the rise of Islam. No Prester John was to be found in Asia, so European imagination moved him around the blurry frontiers of "India" until it found an appropriately powerful kingdom for him in Ethiopia

 

[Ursa major]

When you find your reference to Ethiopians -- rather than, say, Nubians (who at least have the advantage of living "next door") being closely related to ancient Egyptians, please let us know.

 

[Ray McCarthy]

Ethiopians -- rather than, say, Nubians

Hmm ... Nubians?
Maybe my memory is confused

 

[Dave]

Most books on African history that were written more than, say 40 years ago, are probably unreliable as they were written from a totally European perspective, and deliberately began with the premise that Africa had no history before Europeans civilised them. This was necessary to defend the European colonisation of Africa as being in Africa's best interests. This may even be true of books written since independence since the authors would have still been educated with that same Euro-centrist viewpoint. There is, however, plenty of archaeological evidence of great African civilisations in the past.

I feel the discussion has strayed a long way from the OP though. If the theory is that stress of the parents switches on previously dormant genes in the offspring then I can accept that as a theory. That would also work for skin tone, but I think that would be a much harder one to prove, given the environmental factors involved in skin tone - for instance, I'm quite brown skinned at the moment - nothing to do with my parents but the fact that I've been working outdoors most of this year. Given that richer people tend to do less manual work and have office jobs then the you would expect them to get paler skins. Who can say that, given the same exposure to the sun, the Egyptians working in the fields wouldn't have the same colour as those cracking the whip in the shade of a papyrus?

 

[Piousflea84]

From a medical perspective, it's highly plausible that starvation, cold exposure, torture etc could result in physiological changes in eggs/sperm that could be passed on to children. This is even more likely if injurious conditions persist during pregnancy - for example, a Holocaust survivor is still suffering from PTSD when she becomes pregnant post-war, so her hormonal status is different from someone without any traumatic experiences. This is entirely scientifically plausible and very different from the Lamarckian superstition where wearing heavy earrings causes your children to be born with big ears.

The research on mice and cherry blossoms is much more interesting, because it at least suggests a possible mechanism for so-called "genetic memory". That said, it is a single study that hasn't been replicated (as far as I can tell). If you click on the Nature link, even the original article has quite a bit of skepticism about the results.

Coming from a molecular biology background, I find it highly implausible to think that a sperm could carry enough any significant percentage of someone's life experiences. A human genome contains approx. 3 billion base pairs, the equivalent of 750MB of information. If you assume 10 bytes of epigenetic information for each byte of genetic information, you get 7.5GB of data in a sperm. That's one movie DVD's worth; nowhere near enough data to hold all of the significant events in your life. It is plausible that hormonal+psychological conditions during pregnancy could impart a much larger amount of hereditary information, but this would be a strictly mother-to-child phenomenon.

***
Re: the Great Threadjack: Skin pigmentation is very much genetically determined, not epigenetic. You can't flip someone's skin color just by exposing them to sunlight for a few generations - just ask any bloke from Australia, mate. There is a huge difference in skin tone between a really tan white guy and someone from India, Nigeria, etc. The phenomenon of "light skinned Africans", "dark skinned Frenchmen" etc are entirely due to interbreeding and not any sort of Lamarckian effect.

http://www.nature.com/jid/journal/v132/n3-2/full/jid2011358a.html

 

[Stephen Palmer]

A famous example of epigenetics.

 

[Ray McCarthy]

There is a huge difference in skin tone between a really tan white guy and someone from India, Nigeria, etc.

Yes. But babies can be born darker because their very pale parents moved to a much sunnier clime. It's not about the child's actual exposure to sunlight. If I find the article, I'll link. So it may not be entirely due interbreeding, was the article conclusion.
May not be true for India. For Nigeria it's true.