April 1, 2011

Horse's double origins

Pootok arra Orbelaunen
Pottoka
The archaeological evidence was very much inconclusive in this matter of where modern horses originated. While horses were obviously central to Paleolithic cultures of SW Europe, who ate and painted them with almost religious devotion, since the end of the Ice Age and until the Metal Ages there is a fossil gap on horses, not just in SW Europe but also everywhere else.

Then the first domestic horses show up in the Eurasian steppes, north of the Caspian Sea, (notably Botai culture but also Samara and Dniepr-Don) and there is a clear expansion of this animal along the routes taken by the Indoeuropean invaders of the Kurgan cultural phenomenon.

In this sense, some believed that horses had gone extinct in SW Europe upon the arrival of Holocene. A new paper challenges this idea based on genetic diversity:


Abstract

The role of European wild horses in horse domestication is poorly understood. While the fossil record for wild horses in Europe prior to horse domestication is scarce, there have been suggestions that wild populations from various European regions might have contributed to the gene pool of domestic horses. To distinguish between regions where domestic populations are mainly descended from local wild stock and those where horses were largely imported, we investigated patterns of genetic diversity in 24 European horse breeds typed at 12 microsatellite loci. The distribution of high levels of genetic diversity in Europe coincides with the distribution of predominantly open landscapes prior to domestication, as suggested by simulation-based vegetation reconstructions, with breeds from Iberia and the Caspian Sea region having significantly higher genetic diversity than breeds from central Europe and the UK, which were largely forested at the time the first domestic horses appear there. Our results suggest that not only the Eastern steppes, but also the Iberian Peninsula provided refugia for wild horses in the Holocene, and that the genetic contribution of these wild populations to local domestic stock may have been considerable. In contrast, the consistently low levels of diversity in central Europe and the UK suggest that domestic horses in these regions largely derive from horses that were imported from the Eastern refugium, the Iberian refugium, or both.


BGD Ranch's Caspians
Caspian horse
Notice that all but one of the samples from the Iberian peninsula are from the North and that also Occitan horse breeds like the famous Camargue show very high diversity. Hence talking of Iberian refugium may be a misnomer and we should better talk of SW Europe.


In the Eastern area, there is a limitation of sampling sites, with only two breeds representing all the potential diversity once extant in Eastern Europe, West and Central Asia. These are the Caspian horse from Northern Iran and the Ahal Teke breed from Turkmenistan (also very popular in Russia and the North Caucasus).

The essence of the results of this study is visible in fig. 1:




3 horses on pasture
Camargues
Following table 2, the highest genetic diversity (Nei's H) of all surveyed breeds corresponds to the Occitan and Basque horse breeds: Camargue and Pottoka (H=0.776 and H=0.775 respectively). Follow closely the Caspian horse of Iran (H=0.770) and the Garrano of Portugal (H=0.763) and the Galician horse (caballo gallego, H=0.762).

Another way to measure diversity is allelic richness (Rs). By this measure, the most outstanding breed is the Galician horse (6.82), followed by the Caspian horse (6.70), Garrano (6.56), Pottoka (6.52) and Camargue (6.43).

Overall we find that these five breeds cope all the highest diversity positions, being all from SW Europe, except the Caspian horse.

Caballo tipico gallego
Galician horse
Garrano-02
Garrano

See also in this blog: Horse had multiple domestication events (ancient equine mtDNA) (Dec 2010).

8 comments:

  1. One wonders if the population structure in horses doesn't have a parallel in the population structure of epi-paleolithic people.

    Were there highly segregated populations of pre-farmer hunter-gatherers in forested and non-forested areas, which presumably took very different lifestyles?

    The presumably farmer biased lore of legend and fable suggests immense fear of forests (this could also be an artifact of horse centered Indo-European cultural roots as horses aren't best suited to forests).

    The fact that Italy was a largely forested refugia, while the Franco-Canibrian and SE European refugia were largely unforested is also interesting. What impact did that have?

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  2. That map is an approximation, first of all. For example it is known that much of Iberia was densely forested in part of the Epipaleolithic period, corresponding (it seems now) to a peculiar "macrolithic culture" based on saw-toothed implements (once confused with a facies of Mousterian).

    For what it matters all the West and Central parts of Europe were of Magdalenian and then "Epi-Magdalenian" culture (Azilian, Sauveterre-Tardenois), excepting the far North, which corresponds with the Ahrensburgian-Hamburgian-Maglemosean tradition, which seems to be a different one.

    I speculate this one corresponds to Y-DNA R1b1a2a1a1a (M405/S21/U106), while the Magdalenian-plus tradition would correspond to R1b1a2a1a1b (P312/S116) - see here for details on their distribution and relatedness.

    "The presumably farmer biased lore of legend and fable suggests immense fear of forests"...

    Not Basque mythology. But Basque mythology does not seem to fear almost anything, as long as you are respectful. Also Basque farms are typically scattered through the forest ('baserri': farmhouse but literally "forest village").

    "... this could also be an artifact of horse centered Indo-European cultural roots as horses aren't best suited to forests"...

    It could well be indeed. Resistants to all Indoeuropean invasions must have found refuge in the forests, where they could deploy guerrilla tactics Robin Hood style.

    But for the Celts, the most Western of all Indoeuropean peoples, forests were sacred anyhow (yet druidism seems to have been imported from pre-Celtic Britain - hard to judge where each element fits).

    "The fact that Italy was a largely forested refugia, while the Franco-Canibrian and SE European refugia were largely unforested is also interesting. What impact did that have?"

    No idea but I'm guessing that the map is just too approximate to reach to any conclusion. For example NW Iberian paleobotanics were explained in great detail here. While they do not reach to as late as 6 Ka ago, I understand that at that time vegetation was like modern (prior to human intervention - mostly). And NW Iberia today would be a land of oaks would not for the industrial plantation of pines and eucalyptuses. Same for all the northern strip of the peninsula.

    It is anything but "dry" (ask my English roommate who always complains that it rains more here than in London).

    Also forest and pottokas are more compatible that one may think. Your typical established oak forest is not that dense but actually a nice place to walk through, even for a horse, specially a small one.

    In general, highly forested areas would have supported smaller populations, I presume - but unsure. But that map is anything but trustworthy in any case.

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  3. "Resistants to all Indoeuropean invasions must have found refuge in the forests, where they could deploy guerrilla tactics Robin Hood style."

    Just what I was getting at, and your comment seems to resolve the timing of anti-forest legends.

    "(ask my English roommate who always complains that it rains more here than in London)."

    I think I'll wait for reports from the daughter of my good friend who is in Pampalonas now as part of a half year study abroad program. Then again, living in the arid West, we stop everything to go out and get wet and frolic every time it rains, so she may be ill suited to know the difference. The local saying is that ranchers use tin roofs so they can deceive themselves into thinking the rain is more than it really is. Then again, within the last week we had 84 degrees F (about 37 C) followed by snow the next day, our weather is just weird.

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  4. Pamplona is more arid than this: it is in the Mediterranean side of things, in the Ebro basin. It's still so-so because it's the piedmont but not anymore the Atlantic strip (or the Pyrenees), where woodlands are clearly and spontaneously hegemonic (in absence of human intervention).

    It's not like the rainforest... but almost: it rains every other day (sometimes A LOT) and it's only cold like 1/3 of the year.

    "Then again, within the last week we had 84 degrees F (about 37 C) followed by snow the next day, our weather is just weird".

    Kinda hot for early Spring, right? Even if the climate is continental it should not be that hot until June or so I understand. Much less followed by snow. :D

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  5. Beautiful write-up and pictures. Made me mad that Portugal's military just flat out decided to alter the ancient make-up of that horse breed (oh, wait, I didn't read that here, but in one of the wikipedia entries on these horse breeds). Do some of them look almost like wild undomesticated horses, or maybe it's just a pseudo-look because they're pony-ish.

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  6. I was not really aware how all were small horses. Being used for riding, I thought that the Garrano and Camargue would be larger - but seems not. The Camargue horse is famous for the cowboys and bull riding - I did not really expect the horse to be small (they do not look that small here nor here).

    But I guess that most ancient horses were small and that a larger size is a feature selected by breeders. Przewalski are not large either.

    ...

    Btw, Andrew, 84 F = 29 C, almost 10 degrees less than what you say. Hot but not so extremely hot.

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  7. For the record, in the ancient mtDNA paper, Garrano horses (as well as other West Iberian breeds) show up as having local Iberian 'grandmothers', while Pottokak have continental ones, which may be even 'Siberian' at the Paleolithic stage.

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  8. "Kinda hot for early Spring, right?"

    Apologies for the bad conversion. Still, it was hot for early Spring - eight degrees F (a little less than five degrees C) above the all time record high for that day of the year. New records aren't that unusual, but that huge a jump over record highs and that rapid a change in temperatures is remarkable.

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