Monday, March 05, 2007

Monday Maps - Lactase persistence in Europe

I have several maps today. Still intrigued by the lack of the supposed lactase persistence allele (LCT 13910-T) in the 7 European Neolithic skeletons, I was trying to find a map of the frequency of that allele across Europe (or the world). This was mainly an internet search, and I only looked at a few of the published papers. This is what I found:
This one (above) shows the percentage of people who are lactose intolerant (however that was measured??)
This one shows pretty much the same thing, but inverse - those who are lactose tolerant -- here again, highest in Northwest Europe and not all that high in central, eastern, and southeastern europe (where those neolithic skelonts were found)
This one shows the lactose absorption across Europe. This is from the website of Karin Haack, a PhD student interested in "Exploring human diet in prehistory through the genetic trait of lactase persistence". In referring to this map, she says:

"Looking at the map of percentages for lactose absorption in Europe one can see a distinct cline from the north-west to the south east. This is very interesting for the following reason: animals were domesticated in the Near East around 10,000 years ago and then subsequently spread over Europe till animal domesticates reached the British Isles around 6,000 years ago. One would therefore expect populations in the Near East to have highest percentages of lactose absorption and populations in north-western Europe to have lowest percentages of lactose absorption, if lactase persistence was selected for with the domestication of animals and development of dairying. But percentages for lactose absorption are highest in those regions where domesticated animals arrived last in Europe not where animal where domesticated. Therefore the selection for lactase persistence should be a north-western European event which essentially means that there should be multiple origins for lactase persistence all over the world since high percentages occur elsewhere in the world. An indication that there must be multiple origins for lactase persistence is given by my revision of genetic data generated by Hollox et al. (2001)."

Well anyway, one of my points for this long post is that the absence of the LCT 13910 allele in the Neolithic skeletons may not be inconsistent with the relatively high frequency of lactose intolerance in many parts of Europe. There are still many unanswered questions, for me at least. Do we know the allele frequency of 13910-T in different parts of Europe today ?(we probably do) and to what extent is that the causative allele (any physiological evidence?), and finally, to what extent is the phenotype plastic?

9 comments:

Dude in Hammock said...

I'm not sufficiently expert in these matters to know whether or not this is a viable theory, but what if lactase tolerance didn't originate with domesticated cows, but with reindeer? There is a very long tradition of the Laps having semi-domesticated reindeer as the central part of their culture and diet (I know that they even drank reindeer piss after the animals ate amanita muscaria, and the piss was psychoactive), so milking them doesn't seem an impossibility. If true, this would explain the conundrum of the numbers you discuss.

Yann Klimentidis said...

I'm not sure what to think about this . How would reindeer milk explain the absence of lactase persistence in those neolithic skeletons? lactose is the same in cows as it is in reindeer, I would guess.

Rancher said...

The gene for lactose tolerance in Europe originated in Scandinavia. It first became expressed when the Funnelbeaker culture introduced animal husbandry to the area about 4000 bce. The prevalence of the gene is nearly universal in the territorial extents of the Funnelbeaker culture.

The occurrance of the gene in Europe can easily be explained by the migrations of Germanic peoples.

It is quite possible to use milk as a food without being able to digest lactose. Yogurt and cottage cheese are just two examples of fermented milk products that are virtually lactose free. The ability to digest fresh milk is a convenience, but only a minimal survival advantage in a pastoral culture. In warm climates, milk doesn't remain fresh for long. If you put milk in a clay pot with a lid, you have cottage cheese within 24 hours.

The lactose tolerance in East Africa is apparently an independent mutation, even more recent than the Scandinavian gene.

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batman said...

What if the origin of domestic animals did not originate in Anatolia, but in the green fields of N Germany, Denmark or southern Sweden?

Isn't the need for extra fat and proteins consequent with the harsher climate of the north, where more energy (work) is required to maintain the basic life-functions than in the tempereate and far more pleasant south?!

Please dont forget that the thesis of the fertile crescent - as THE origin of everything - is no more than a hypo-thesis...

Viagra Online said...

hi Yann!, you found very intriguing pictures and I have the exact same question you asked, how the hell did they measure that? it would have to be a huge census to have a valid percentage, not just a small sample.

Rachel said...

The most recent thinking is that lactose tolerance directly correlates with areas of poor soil and high rainfall and/or cold climate. Upon the adoption of agriculture, pastoral groups in Northern Europe would have relied more on fresh milk as an immediate calorie and protein source because of the difficulties in growing crops, coinciding with the stress on wild resources arising from the 8.2ka and 4.2ka event (http://books.google.com/books?id=RA1hTh34LDYC&printsec=frontcover&dq=holocene&hl=en&ei=LvrrTJXkLcLNhAf4ioXODA&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCMQ6AEwAA#v=onepage&q&f=false)
@batman: the origins of farming in the Fertile Crescent is not a thesis, it's been proven through extensive flotation during excavation and rigorous and widespread dating on many remains, including carbonised seeds and pottery.

Anonymous said...

hi,
the northern german deep plain (direct under danmark, northern germany) is the center of lactose tolerance and viking gene like Y-haplo R1a & R1b.
The lower difference cames from the immigrations in the last 1000 years from non-lactose tolerant country. Scandinavia had not so a lot emigrants = it came to a higher concentration of lactose tolerance. German genetic is in 60% of all north and middle europeans like uk, irland, island, france, austria, northern italy, poland, balcan, balticum and so but the nordish countrys is not really interesting for immigration, too cold for the most.

50 Mio Americans say, she have german roots in her tree. The most cames from England, German, Netherlands, east France, west Poland and south Scandinavia = all country with lactose tolerance region about 60%.
The source is a small population from balkan (not more as 1000 people with R1a and R1b genetic) what is immigrated to german before 5000 BC and build the german tribes with this genetic. the origin celts and slavic was not lactose tolerant! It exist a hard break in the middle of poland, austria and france.

And interesting, the blond hair came from the russian tundra northern black sea. It is not a scandinavian mutation of the sun, but the same effect - isolation and concentration.
The region of euroasian tundra before 1000 BC has a european phenotype before the darkhair turkfolks came later like attila. A lot kurgans from caucasus, altai, mongolia to nw china had blond hairs and nordish phenotype.
But this openings is not good for national interests.

Spontan translate from german archeology results. greets and sorry for bad english. i hope it is understanding.

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