This is an extremely important study as it establishes the occurrence of lactase persistence in Neolithic Europe. This invalidates the idea proposed by some about a very late (post-Neolithic) introduction of lactase persistence into Europe by a pastoral population from the east, since we now have good evidence about the presence of this trait in a Neolithic sample from Atlantic Europe.
The frequency is higher than in the early Neolithic Linearbandkeramik (where it was absent in the tested samples), and lower than in present-day Basques, although levels of 27% are quite comparable to some modern south European populations. We are unlikely to detect the earliest occurrence of this trait (when it was limited to the original mutant and his descendants, prior to having a substantial advantage for digesting milk), but the new findings represent a new non-zero data point in the time series, which will certainly fill up as more points in space and time are tested.
European Journal of Human Genetics advance online publication 11 January 2012; doi: 10.1038/ejhg.2011.254
Low prevalence of lactase persistence in Neolithic South-West Europe
Theo S Plantinga et al.
The ability of humans to digest the milk component lactose after weaning requires persistent production of the lactose-converting enzyme lactase. Genetic variation in the promoter of the lactase gene (LCT) is known to be associated with lactase production and is therefore a genetic determinant for either lactase deficiency or lactase persistence during adulthood. Large differences in this genetic trait exist between populations in Africa and the Middle-East on the one hand, and European populations on the other; this is thought to be due to evolutionary pressures exerted by consumption of dairy products in Neolithic populations in Europe. In this study, we have investigated lactase persistence of 26 out of 46 individuals from Late Neolithic through analysis of ancient South-West European DNA samples, obtained from two burials in the Basque Country originating from 5000 to 4500 YBP. This investigation revealed that these populations had an average frequency of lactase persistence of 27%, much lower than in the modern Basque population, which is compatible with the concept that Neolithic and post-Neolithic evolutionary pressures by cattle domestication and consumption of dairy products led to high lactase persistence in Southern European populations. Given the heterogeneity in the frequency of the lactase persistence allele in ancient Europe, we suggest that in Southern Europe the selective advantage of lactose assimilation in adulthood most likely took place from standing population variation, after cattle domestication, at a post-Neolithic time when fresh milk consumption was already fully adopted as a consequence of a cultural influence.
Link
28 comments:
It is ridiculously low: the levels are within the Italy-Greece-Poland range (modern for the LCT allele: real lactose tolerance is much higher).
Do you know what site it is because the results may be hinting to a settler Neolithic population of (largely) different stock than modern (and ancient) Basques, so I am imagining some Ebro banks site like San Juan APL. Am I right?
The difference in the frequency of the relevant allele between the tested Neolithic samples and the present-day inhabitants of the same region is huge. It is unlikely to have been just due to the local dynamics. Migrations from outside seem to have played an important role in the change of the allele frequencies during the intermediate period. Basques or Proto-Basques must be post-Neolithic arrivals to that region.
"It is ridiculously low"
I don't see why it is ridiculously low? A litre of full fat milk is something like 800 calories and the average person needs 2000 calories a day. In environments where producing calories as milk is the most time-efficient choice then lactose tolerance could be a huge advantage but elsewhere only a small one.
So it seems reasonable that lactose tolerance would have been at low levels initially and only grown to very high levels in places where cattle-raising for milk was optimal.
(I assume that would be terrain that was wet with a lot of lush grass but not that great for crops i.e. mountains and atlantic coast e.g Dinaric Alps, Switzerland, Basque country.)
Every famine and extremely bad winter the percentage would go up slightly as more LP people survived.
I'm not much in agreement with what you say Grey, mostly because milk and dairy are not the staple food in any society... except probably those exclusively dedicated to livestock herding, in the steppe belts of the world - not in Atlantic Europe. However even these hyper-diary diets like those of the Fulani or Mongols and such have not made them to have such extremely lactose tolerant phenotypes. You can argue that Mongols eat yogurt and the Maasai mix the milk with blood... but Basques made cheese, had a varied diet and still are extremely latose-tolerant.
It's probably a fluke to some degree at least because there's no reason why people eating mostly corn and fish (or corn and meat and eggs and veggies), with just some dairies in the diet, would be so extremely selected to be lactose tolerant.
Basque milk is for kids, for desserts (delicious but evolutively trivial), for cheese and little more.
...
Whatever the case I can confirm that the two samples are from the Ebro river banks: San Juan APL in Arabako Errioxa (aka Rioja Alavesa) and Longar in Navarrese Rioja.
This area per my manual of Basque Prehistory was colonized mostly (although not exclusively) by "gracile-Mediterranean" types who had migrated apparently up the river upon the arrival of Cardium Pottery culture Neolithic peoples. Previously, in the Epipaleolithic, there had been a migration from North to South of peoples of Pyrenaic type (proto-Basques presumably) but both flows may have met in the Ebro river banks.
I do not think these samples can be considered "Basque" without qualifications (in athropological contexts). Although they clearly are from the areas generally acknowledged as part of Euskal Herria (= Basque Country) or the seven historical Basque provinces, this is a historical and political construct rather than an anthropological one.
All one needs to be lactase persistent is one "T" at 13910. So, if just one parent passes that on - voila! - you're a milk drinker for life. Thus a figure of 27% in a Neolithic population could easily rise over time to the levels we see today - and without an influx of lactase persistent outsiders.
Surely some of those remains were male. I am wondering what their y haplogroup(s) were.
It is unlikely to have been just due to the local dynamics. Migrations from outside seem to have played an important role...
Onur,
I never understand this argument. People in most of Europe had about the same amount of time to establish lactose tolerance. You are just shifting this "quick evolution" to another population.
In fact, some of the areas with the highest levels of tolerance are the ones in which agriculture and cattle farming were introduced last (UK and Scandinavia).
Also, milk contains vitamins D and folic acid, so it can extend the range of skin color that is optimal for given sun shine conditions - which is particularly useful in regions with large seasonal effective sunlight fluctuations (due to fog, cold temperatures, and/or high latitude). Calcium also plays a role.
Maju, "from the sites of Longar
(Navarre) and San Juan Ante Portam Latinam (Araba)" - that is fairly far southwest.
I never understand this argument. People in most of Europe had about the same amount of time to establish lactose tolerance. You are just shifting this "quick evolution" to another population.
No, I am not. We currently do not have enough data to make a European or West Eurasian frequency map of the relevant allele during the Neolithic times or the intermediate period between the Neolithic and present. There may have been areas high in the relevant allele frequency during the Neolithic; we just do not have enough data to know whether there were or not.
In fact, some of the areas with the highest levels of tolerance are the ones in which agriculture and cattle farming were introduced last (UK and Scandinavia).
I am not entering into the question of whether the relevant allele or the lactase persistence in general had any evolutionary advantages for their carriers and to what extent. That is a very speculative subject, at least for now.
A timeline of 4500 BP to 5000 BP is Copper Age, not Neolithic, and the percentages are consistent with a transition era in terms of LP. Roughly speaking, in Basque Country, this timeline corresponds to a marked increase in cattle farming and corresponds to the influx of Bell Beaker people to the area who have a different physical anthropology from the original Neolithic people of Iberia (I'd be interested to see what relics and physical anthropology are associated with the sampled population). I've spelled out some of the pertinent contextual data points for the region in that era here.
This supports, rather than contradicts, the notion of LP in Southern Europe as a product of a metal age migration (although in this particular case, a migration from the North, rather than pastoralists from the East, is a better fit with archaeological cultures of the region).
Also, it isn't just LBK Neolithic samples that lack LP. It was also very low in a recent early Neolithic ancient DNA sample from Gascony, a population than then and now was low in LP.
How did the current distribution come about? A plausible theory is that LP provides significant selective advantage in Northern Europe and the European Steppe (where good alternatives to milk fats like olive oil are not widely available), but far less in Southern Europe where a mild climate, temperatures inappropriate for storing cow's milk for extended time periods even in winter, make LP less helpful. In this scenario, LP becomes more common someplace where it provides a strong selective advantage, and then, that population migrates into Southern Europe
Actually, Unknown, the data is for the T-allele apportion, not the phenotype. But it does not change much because there are double TT than TC people in both sites (strongly suggesting recent admixture in my opinion).
SJAPL: 4 TT, 2 TC, 13 CC
Longar: 1 TT, (0 TC), 6 CC.
"I am wondering what their y haplogroup(s) were".
While there is no one-on-one list that I know of, these two samples are the same (but reduced in number because of many failed analysis, I understand) as those in Izagirre and de la Rúa 1999 (however that paper only reports inferred haplogroups and does not list mutations, so its relevance is very limited).
>But it does not change much because there are more* double TT than TC people in both sites (strongly suggesting recent admixture in my opinion).
Good catch maju. It does suggest a recent migration but the question is what's the scale. Are they from a nearby town or from many miles away and represent a different people. It would be nice if they had better racial indicators.
Andrew thinks it might be bell beaker peoples from the north. Do you think they could have been individuals high in double T?
Also the wiki article on the bell beaker culture says most of its places experienced racial discontinuity apart from the Czech republic and northern Spain. Maybe there were exceptions...
Look, Duadha, I can't discern every single element playing here and I do not believe in "races" (at most in morphotypes, which may be hereditary or not).
But I know that Wikipedia is pretty much wrong in that claim of "racial discontinuity": not only most BB sites everywhere appear to be burials of local people according to morphotype (with the rare exception) but also (maybe outside Germany and immediate surroundings) BB is a minority phenomenon within larger cultures (essentially Megalithism), much as Jews could be in Medieval Europe, for example.
"mostly because milk and dairy are not the staple food in any society... except probably those exclusively dedicated to livestock herding"
I agree it would have needed extreme circumstances to cause such a big shift in frequency but if you have a selectable trait with a very high frequency then it is plausible it was selected for?
For example if a population moves into a region where their existing agricultural package doesn't work as well or adopts a package that works in an adjacent region but not in theirs i.e. they produce less crops than usual but more milk, then those who can drink milk can switch to having more cows, drink half of it every morning and dairy the rest.
The thing about drinking the milk is you save the time spent dairying and that time can be used for something else like fishing or foraging.
So the selection pressure would have been applied early on as either a migrating people adapted to a new environment or an existing group adapted to a new way of producing food.
I think some are underestimating the benefit of milk (before poor people were able to afford a healthy diet and/or vitamin pills).
Poor people, including poor farmers, often had a diet that was only healthy seasonally. Since the advent of agriculture, loads of empty carbohydrates were substituted for overall healthy, nutritional food.
If a male was able to drink and digest milk from years 6 to 25, i.e. in the time he likely fathered the first 1-4 children, he was taller, stronger, healthier, had better bone density, and likely overall was more attractive than his peers. And because his mate(s) drank milk, they did not suffer from catastrophic folic acid or calcium deficiency, and bore much healthier children than average - to a local group culture that propagated these nutritional practices.
Building on two points by Maju:
"I do not think these samples can be considered "Basque" without qualifications (in athropological contexts)."
"there are double TT than TC people in both sites (strongly suggesting recent admixture in my opinion)."
Honestly, from what I've seen of the archaeological evidence, this time period of 3000 BCE to 2500 BCE is right around the point at which Basque ethnogenesis in an anthropological and cultural sense is probably taking place, and recent admixture is probably part of that process.
@Andrew: why do you say that? I see nothing peculiar happening in the 3rd millennium of all times.
@Eurologist: what's the difference between drinking raw milk or eating cheese, something that all lactose intolerant people can do very well? Basque have been making and eating cheese since immemorial times but for that they needed not to be lactose tolerant.
You may be right about proteins and other nutrients but why would milk be more easily available or less in this or that area? Didn't Greek farmers have goats and sheep and got milk from them? Indeed. Whether they consumed the milk as feta cheese or raw (a rare practice anywhere) does not make much of a difference. Similarly butter can be eaten regardless of lactose tolerance status, only basic milk but not other dairies is what is partly unaccessible to lactose intolerant peoples.
I really don't know of any culture in which drinking so much raw milk was important, except among peoples who are in fact largely lactose intolerant like Mongols or Maasai, nomadic pastoralists who must "trick" the milk in order to be able to digest it (and they do, demonstrating once again that culture is at least as efficient if not more than genes).
what's the difference between drinking raw milk or eating cheese, something that all lactose intolerant people can do very well?
It all depends on whether the cheese is fermented, since some ferments consume the lactose.
> This invalidates the idea proposed by some about a very late (post-Neolithic) introduction of lactase persistence into Europe by a pastoral population from the east
It's in the time frame of the copper age and the beaker people who some say came from the east and spread IE to western Europe.
> I do not believe in "races"
I was using races in a relative sense... I just meant people with a different heritage and different inherited trates, especially craniometry.
> But I know that Wikipedia is pretty much wrong in that claim of "racial discontinuity"
Here (http://www.buildinghistory.org/distantpast/bellbeaker.shtml) is another reference that specifically sites the evidence.
They latter say that there was discontinuity at most BB sites apart from the southwest. It may have been a more elite transition there but still bringing the LP trait there.
> what's the difference between drinking raw milk or eating cheese, something that all lactose intolerant people can do very well?
Nutrition, time, energy, and know how.
> Look, Duadha
Lol, your just making yourself look bad... errrrr, worse : )
"what's the difference between drinking raw milk or eating cheese"
time spent dairying
"why would milk be more easily available or less in this or that area?"
Well that would be the condition. If that situation could arise then it's plausibly selective. If not it isn't.
It would have to be somewhere where grass was very lush and plentiful but crops were weak - at least before new strains were developed better suited to that area.
My guess would be higher (and wetter and colder) altitudes i.e mountainous regions and along the Atlantic coast. If so the highest rates of LP would be
- Dinaric Alps
- Swiss Alps
- Carpathians
- Pyrenees
- Atlantic coast
and the highest of all would be where you had both conditions like the northern coast of Iberia and the mountains along the west coast of Ireland.
http://www.euratlas.com/Atlasphys/euromont2.jpg
That wouldn't prove the theory was true but it might disprove it if there was no match.
If those same areas also had the highest levels of things like wheat allergies that might reinforce the theory.
"Didn't Greek farmers have goats and sheep and got milk from them"
Logically that would have to be the second condition. Cattle would have to be more efficient than sheep under some conditions but not others. For the theory to be true cattle would have to be more productive in wetter conditions with lush grass and sheep / goats more productive in dry conditions with more sparse grass.
The same basic idea would apply elsewhere. In a region where the crop package didn't work very well dropping back to some form of pastoralism would be like a fail-safe. The form of pastoralism would depend on which animal was the most productive in that region, some places sheep, some places pigs, some places cattle.
If that theory is correct the only difference with cattle would be it left a genetic marker of where this process of a phase of extreme reliance occurred - maybe - or maybe places where people relied on pigs or sheep for a long time also developed a high frequency of some connected trait but no-one has looked because it's not as obvious as LP?
But before all that the first step would be are those places listed above the places with the highest frequency of LP (and maybe also wheat allergies).
"what's the difference between drinking raw milk or eating cheese, something that all lactose intolerant people can do very well? Basque have been making and eating cheese since immemorial times but for that they needed not to be lactose tolerant."
Maju,
In addition to what Grey said, it is also the combination. When dairy is plentiful and a focus of production, easily-stored protein and fat from cheese and fat from butter are available in addition to the much richer in vitamins, calcium, and instant sugar benefits of fresh milk. Milk also makes otherwise rather empty serials a more complete dish - all while limiting saturated fat intake.
But don't forget the seasonal benefit of milk. Calories available from cheese and butter can be stored, but green leafy vegetables are scarce in the winter, while milk is available year-round. It acts like a buffer that smoothes out vitamin D and Calcium deficiencies during fall and winter, while preventing folic acid deficiency during high sun-hours spring and summer. Being able to at times rely highly on dairy production also protects against climatic fluctuations that periodically minimize serial production.
The fact is that there are two populations "caught in the act" of mixing in this genetic snapshot. I really don't care much if the alleles are adaptive or mere fluke (the same that Rh- or R1b got randomly fixated or quasi-fixated at some point for no reason at all other than drift, the T allele could have done the same) or something in between but I'd expect that, if these alleles would be so extremely adaptive, that they (or rather the actual phenotype) would be dominant in specialist pastoralist populations around the globe.
This only happens in one population: the Fulani (maybe some Arabs too), with others like Maasai, Dinka, Mongol... being in the low end of phenotypic lactose tolerance. And then farmer populations like the Sindhi in the high end. There is reasonably high lactose tolerance even among totally unlikely populations such as the Maori but then Central Asians (with origins in some of the most radically pastoralist cultures of Eurasia) are almost devoid of the phenotype, go figure!
Also I do not see any particular reason to emphasize cows ("cattle"): Arabs don't have cows but camels (and sheep and goats), Basque, Irish and Scots are more commonly associated with sheep than cows and that's actually what we see in early Basque Neolithic as well: plenty of sheep, cows only became important later.
"Also I do not see any particular reason to emphasize cows"
http://www.sheep101.info/dairy.html
"sheep usually produce less milk than goats and much less than cows"
Some googling
=============
http://epp.eurostat.ec.europa.eu/statistics_explained/index.php/Livestock_statistics_at_regional_level
map of dairy cows 2005
http://epp.eurostat.ec.europa.eu/statistics_explained/index.php?title=File:Dairy_cows,_by_NUTS_2_regions,_2005_Dairy_cows_per_hectare_of_total_area.PNG&filetimestamp=20090430100026
SHEEP
Three particular characteristics of sheep mean that they can use land that is too hilly, cold or rough for other livestock:
- their hardiness thanks to the protection offered by their wool;
- their ability to graze on grass that is short or of poor quality;
- their sure-footedness on very steep slopes.
The ability of sheep to cope with relatively arid conditions, and hence poor grass growth, is an important aspect in regions such as Extremadura in Spain.
CATTLE
Unlike sheep, which are subject to footrot in boggy conditions and bloat when feed is too rich, cattle thrive in conditions where rainfall is plentiful and the grass is good
There are two possible modes of milk production. Firstly from cows on grazing land, which requires sufficiently productive grassland
=======================
So seems to me sheep are generally better except in specific locations where there's a lot of flat, wet, particularly lush grassland. (I'd add another possible condition that the same areas would have to be sub-optimal for crops at the same time). In those specific conditions cows produce a lot of calories as milk.
========================
Although this report from Ethiopia seems to suggest camels produce more?
http://www.tropentag.de/2008/abstracts/full/18.pdf
"only the morning milk is sold, while the evening milk is used for home consumption."
Ethiopians lactose tolerant?
Your own first link, Grey, says at the very beginning: "Sheep have been raised for milk for thousands of years and were milked before cows".
I have the strong impression that cows were initially used, at least over here, mostly for meat and work (oxen). The local breed of cow is certainly not a milk breed but a semi-feral one for meat and work. All traditional dairies (cheese, curdled milk) are made of sheep milk. Cow cheese is a Castilian thing.
The same happens in so many other places, even if I'm not privy to each detail of local traditions and archaeology.
Also sheep, not to mention goats, are cheaper (in cost and maintenance) and hence more widely available: if you need a source of milk for everyone (in order to justify the evolutionary hypothesis of the lactose tolerance alleles), I'd say that in most cases goats are the animal of choice, because nearly everybody could own one or more.
Your map of EU's modern cow milk production is not relevant in principle because the methods of milk production in cows nowadays have become radically industrialized and (sadly enough) those cows almost do not see the sun, much less green grass. Meat cows however are in many areas still raised in traditional ways.
"@Andrew: why do you say that? I see nothing peculiar happening in the 3rd millennium of all times.
@Eurologist: what's the difference between drinking raw milk or eating cheese, something that all lactose intolerant people can do very well? Basque have been making and eating cheese since immemorial times but for that they needed not to be lactose tolerant.
You may be right about proteins and other nutrients but why would milk be more easily available or less in this or that area? Didn't Greek farmers have goats and sheep and got milk from them? Indeed. Whether they consumed the milk as feta cheese or raw (a rare practice anywhere) does not make much of a difference. Similarly butter can be eaten regardless of lactose tolerance status, only basic milk but not other dairies is what is partly unaccessible to lactose intolerant peoples.
I really don't know of any culture in which drinking so much raw milk was important, except among peoples who are in fact largely lactose intolerant like Mongols or Maasai, nomadic pastoralists who must "trick" the milk in order to be able to digest it (and they do, demonstrating once again that culture is at least as efficient if not more than genes)."
This whole post is you rattling off your head something you don't obviously never took the time to learn about.
Mongols only drink fermented milk which removes the lactose and the less lactase you produce the more the cheese needs to drier/harder (less liquid component) and be aged, which also removes lactose. But if you've reached the point were you produce no more lactase, like myself, even aged cheese or butter, in large amounts will give you problems as they are not lactose free. And the experience is not a benign one that you'd be temped to gamble with over and over.
http://en.wikipedia.org/wiki/Kumis
During fermentation, the lactose in mare's milk is converted into lactic acid, ethanol and carbon dioxide, and the milk becomes an accessible source of nutrition for people who are lactose intolerant.[10]
Before fermentation, mare's milk has almost 40% more lactose than cow's milk.[11] According to one modern source, "unfermented mare's milk is generally not drunk", because it is a strong laxative.[1] Varro's On Agriculture, from the 1st century BC, also mentions this: "as a laxative the best is mare's milk, then donkey's milk, cow's milk, and finally goat's milk...";[12] drinking six ounces (190 ml) a day would be enough to give a lactose-intolerant person severe intestinal symptoms.
@Maju
"Your own first link, Grey, says at the very beginning: "Sheep have been raised for milk for thousands of years and were milked before cows"."
It also says cows produce much more milk than sheep. If there was a selective advantage and it came from calorie production then quantity of milk produced is one half of the equation.
"Your map of EU's modern cow milk production is not relevant in principle because the methods of milk production in cows nowadays"
The linked page mentions two methods. The first is the traditional method which involves grazing cows on lush flat grassland i.e along the Atlantic coast and some wet high altitude areas like the Alps.
@Justin
"but why would milk be more easily available or less in this or that area?"
Because cows produce much more milk than sheep but only in certain specific areas i.e. along the Atlantic coast and up in the Alps.
@Justin:
"Mongols only drink fermented milk"...
That's exactly what I said: tricking the milk into edibility is easier that tricking the body into milk digestion mode, which needs just too many dead people (or people in very poor shape, unable to effectively reproduce) generation after generation.
Also eating something else, like the meat of the veals, may prove an easier source of proteins after all (that's another way of making milk edible). The only thing for which milk is almost incomparable among foods is calcium (although figs are also a good source AFAIK).
"It also says cows produce much more milk than sheep".
Sure. They are bigger and need more food as well. Poor farmers could never have cows historically, goats on the other side were available for nearly all (sheep are the next best in availability and produce wool).
@Grey:
"cows produce much more milk than sheep but only in certain specific areas i.e. along the Atlantic coast and up in the Alps".
I doubt that is the case. Cows have been used for milk production in many different ecologies but specially the steppes, where agriculture is less of a possibility, and very specially the African steppe (sahel, savanna). The role of cows has been much more obviously important among African pastoralists (first of all, most of which are not lactose tolerant and need to "trick" the milk into edibility as butter and/or as blood-and-milk) and also among those cultures that have declared cows sacred: Ancient Egypt and Hindu South Asia. Again none of these peoples is particularly lactose tolerant.
I find that you are constructing a "theory" on very feeble evidence, sincerely. We know that the role of milk and specially of cows historically in the areas that are mostly lactose tolerant was not so large.
"Sure. They are bigger and need more food as well."
Which is the point about rainy conditions.
http://epp.eurostat.ec.europa.eu/statistics_explained/index.php/Livestock_statistics_at_regional_level
"Unlike sheep, which are subject to footrot in boggy conditions and bloat when feed is too rich, cattle thrive in conditions where rainfall is plentiful and the grass is good. Thus Map 5, which shows the distribution of dairy cows, includes a number of clear contrasts with the previous map, reflecting, in particular, altitude and climate differences. Western Europe lies squarely across the predominant westerly airstreams at this latitude.
///
"I doubt that is the case."
Typically, where these moisture-rich winds strike the coast, rainfall is abundant and as a result rich pasture is available for cattle. The Spanish region of Cantabria falls into this category, as do Bretagne and Basse-Normandie in France. Further north, this applies to the Southern and Eastern regions in Ireland, Northern Ireland and the whole western seaboard of England (however, the mountainous nature of Wales and Scotland means sheep remain important there). A similar well-watered coastal crescent is visible across the north-western part of continental Europe comprising the Oost-Vlaanderen, West-Vlaanderen, Liège and Hainaut regions of Belgium, most of the Netherlands, and into the Schleswig-Holstein region of northern Germany. The ‘coastal rainfall’ effect is less noticeable in the much drier Mediterranean environment but still clearly apparent in Lombardia in Italy, which faces onto winds moving north up the Adriatic, and Malta."
"There are two possible modes of milk production. Firstly from cows on grazing land, which requires sufficiently productive grassland, and from cows kept in stalls."
///
"I find that you are constructing a "theory" on very feeble evidence"
The evidence is very clear. Under certain conditions
- wet
- flat
- heavy rainfall
- lush grass
cows produce much more milk than either cows or sheep produce outside those conditions and much more than sheep do in the same conditions.
The areas of maximum LP coincide with the areas of maximum natural milk production.
I'd rather consider map#3 at your link: grassland per area: which shows that most high dairy regions (Netherlands, Brittany, Lombardy) have limited (or even very low) grassland availability. The areas of high grassland availability are traditionally mostly associated with sheep:
"Sheep (...) are important grazing animals and their distribution is comparable to that of grassland. Regions with the largest proportion of grassland (see Map 3)"...
Milk cow number, is explained later, often depends on imported food, what allows regions like Netherlands or Brittany to produce much more milk than would be sustainable with their own local resources of grass. This industrialized form of production should be removed from all analysis, hence going back to the grasslands' map which is directly identified in text with sheep density.
Hence sheep (if anything) and this is my last post on the matter because we can agree to disagree as well.
"because we can agree to disagree as well"
Indeed, no prob.
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