...approximating those from the Middle Ages
The breeds that were around in the Middle Ages no longer exist. There weren't really "breeds" in the modern sense until the very late 18th century, and virtually all the known modern breeds were developed in the last 200 years. Even a breed labeled as "primitive" or "ancient" has not remained in a vacuum; modern sheep farmers may select for different traits than their ancestors did, which has an impact on the flock's characteristics.
I have compiled a list of some modern breeds that bear a strong enough resemblance to sheep of the Middle Ages that their fleece would be preferable to use in reproduction projects. For the moment I am focusing on English sheep; since England was a strong exporter of wool in this period, their wool ended up across Europe and so is appropriate for a much wider area than just England. (The Spanish merino is a whole different story, which I shall tackle at a later date...)
Middle Ages: The Sheep
There was a great variability among medieval livestock. So, while general observations can be made, keep in mind that the range was much greater.
In general, medieval English sheep are pictured as small white sheep with long tails and no horns. Occasionally rams are shown with horns, while ewes almost never are. However, sheep skulls in the archaeological record prove that while rams were indeed horned, ewes could be either horned or polled (no horns). Skeletal remains also show that sheep were much smaller than modern breeds, and were closer to the size of the modern Soay (ewes average 53 lbs., rams 84 lbs.) or Shetland (ewes 75-100 lbs., rams 90-125 lbs.) By contrast, some modern breeds can reach 300 lbs. or more.
Middle Ages: The Wool
Color: While colored sheep did exist in the Middle Ages, as evidenced by pictorial depictions and surviving textiles, white wool was far more common.
Staple length: Given that most surviving wool has already been made into something, staple length is difficult to determine. Four unspun wool samples from Perth show a range of 1"-2.4" in length, but of course that is only four samples. One reason for the popularity of English wool was that it was reportedly longer than its Continental cousins, and therefore made better worsteds, where the fibers are combed instead of carded. I think it is safe to assume, however, that staple lengths like the modern longwools (developed in the late 18th century) of 10" or more were unlikely to have been around.
Fiber diameter: This is much easier to determine from remaining wool samples and textiles. One study of English medieval wool from two sites, Perth and Aberdeen, shows a range of fiber fineness and percentage of hairy fibers. M. L. Ryder's hypothesis is that the two main wool classifications of the Middle Ages, coarse and fine, correspond to what he calls "hairy medium" and "general medium." The summarized measurements of these two groups are below. Range is the modal range, in which the outliers have been omitted. For the full chart, see M. L. Ryder's "Medieval Sheep and Wool Types" page 27.
- Hairy Medium (medieval "coarse"): 20-40 microns, 17% medullated
- General Medium (medieval "fine"): 20-31 microns, 3-4% medullated
While the majority of the 105 samples fell into these two categories, there was quite a range overall of both diameter and medullated fibers: 10-128 microns and 0-65% medullated. This encompasses everything from the modern Merino (with ranges from 11-26 microns) to the sturdiest carpet wools-- a testament to the wide variety of sheep in the era before recognized breeds.
Here is a list of modern breeds with enough characteristics to medieval sheep and wool that their wool would be preferable to use for reproduction projects. None of these sheep is a perfect match, remember; hundreds of years have come and gone, with changes in everything from livestock breeds to the English language. I have indicated what makes these sheep "close enough" to medieval sheep, and what does not quite match up. Breeds are listed in alphabetical order.
The Sheep: Cheviots are white-faced sheep. Both sexes are polled (no horns). Ewes average 120-160 lbs., rams 160-200 lbs., larger than medieval sheep but not quite so hefty as the more modern meat breeds. They are also relatively independent and need less husbandry than some breeds.
The Wool: Staple length is about 3-5" and 27-33 microns. The wool's helical crimp gives it both durability and resilience, important qualities to consider when making an item that will receive some wear. Cheviot wool probably fits in between the medieval "coarse" and "fine" classifications, and would depend on the individual sheep.
The Sheep: If any sheep has a possibly legitimate claim to being virtually unchanged since the Middle Ages, it's the Icelandic. They were brought to Iceland by the Vikings about a thousand years ago where they remained isolated. It is now illegal to bring any other sheep to Iceland. As a result, this breed is genetically the same as it was in the Viking era. Icelandic sheep were first brought to North America in 1985, then again in 1990, and all Icelandic sheep in North America are descended from these two groups. Keep in mind that any Icelandic sheep outside of Iceland might have been crossed with something else at some point; check the sheep's records to be sure. Why am I including a breed from Iceland in a discussion of English sheep? Because of their isolation, Icelandics show many characteristics of medieval English sheep, and as the Vikings visited England in addition to other places, it is likely that this type of sheep was found in a much wider range at the time. All Icelandics are mostly horned, though some of either sex can be polled. Despite their ancient ancestry, Icelandics are still larger than skeletal remains of medieval English sheep: ewes are 130-160 lbs. and rams 180-220 lbs. They also have a naturally short tail while most medieval depictions show long-tailed sheep. These sheep are quite hardy, have strong immune systems and are relatively independent.
The Wool: Icelandic wool is dual-coated, a more primitive feature that there is some evidence of in medieval textiles. The coarser outercoat has a staple length of 4-18" and 27-31 microns; the softer, wooly undercoat is 2-4" long and 19-22 microns in diameter, definitely a good medieval "fine". Both coats can be spun together or separately. Icelandics exhibit a dizzying variety of colors and patterning, including all-white (a good medieval choice), black, brown, gray, and various patterns including spotted.
The Sheep: Ryeland sheep seem to be the descendants of the famous "Lemster" (Leominster) wool sheep. They are relatively small for modern sheep, with ewes averaging 141 lbs. and rams 192 lbs., though this still makes them much larger than medieval sheep. Both rams and ewes are polled. Varieties in the British Isles and Australia have retained the older characteristics than those in New Zealand.
The Wool: The staple length is 2-5" and the micron count (for the British Isles varieties) is 25-28. This puts the wool within the ranges of medieval samples, for both length and diameter, and would be a good medieval "fine" wool. The shorter staples would be ideal for carding, while the longer ones could be combed. Both white and colored varieties exist.
The Sheep: As you might expect, this sheep has a black face. Both sexes are horned, with ewes averaging 140 lbs. and rams 180 lbs.
The Wool: The fleece is always white. Staples are long, 6-14", so you would want to select something on the shorter end to approximate medieval wool. While the diameter ranges from 28-40 microns with some kemp, the fiber is generally described as both coarse and strong. This would be a good choice to match the medieval "coarse" classification.
The Sheep: This is another breed that retains many primitive characteristics. It is small, with ewes usually 75-100 lbs. and rams 90-125 lbs. It is similar in size to the skeletal remains of medieval sheep. Both sexes can be either horned or polled, although ewes are normally polled.
The Wool: Shetlands are known for variety! They can be either single or double coated, the latter of which is a more primitive feature; there is some evidence of double-coated fleeces being used for textiles in the Middle Ages. There is a great variety in fleece color and patterning, and while there were some colored sheep in the medieval period, solid white was more common. Shetland staples are usually 2-4", a good medieval length, though some can have staples up to 10" (which should probably be avoided for a medieval representation). Fiber diameter ranges from 20-30 microns. Fleeces without much kemp would probably be considered a medieval "fine" wool, while the more kempy varieties would be "coarse."
The Sheep: This is the size of medieval sheep: tiny, compared to modern breeds. Ewes average 53 lbs. and rams 84 lbs. They display the usual medieval horn patterning too: rams are horned, and ewes can be horned or polled. The Soay is considered a feral breed and displays many characteristics of ancient sheep: it is quite variable in appearance, it naturally sheds its wool, and has a double coat. It does show signs of alteration through breeding programs though, so it is not a completely wild variety.
The Wool: The staple length of 1.5"-4" falls perfectly within the medieval range, as does the typical fiber diameter of 29-36 microns, with a fair amount of kemp, making it a medieval "coarse". However, this sheep always has some type of coloring pattern; in the Middle Ages, while there were colored sheep, most were white.
The Sheep: Let me be clear: the Southdown breed was developed in Sussex in the late 1700s. It is not a medieval sheep. However, it is older than many modern breeds and has characteristics that are similar to its medieval ancestors. For instance, it is still on the smaller side, with ewes weighing in at 130-180 lbs. and rams at 190-230 lbs. Both sexes are naturally polled.
The Wool: A staple length of 2-4" and micron count of 23-29 with very little kemp makes it a good choice for approximating a medieval "fine" wool. Nearly all Southdown fleeces are white with only a few colored individuals, which exhibits a typical medieval mix.
The Sheep: Welsh Mountains have naturally long tails, like many sheep do (including those in the Middle Ages). Ewes are polled and rams are usually horned. Adults average 100-130 lbs., making them a smaller sheep and closer to the medieval size than most.
The Wool: Welsh Mountains can be all white, white with black markings on the face ("badgerface"), or all-black. For the medieval effect, all-white is preferable, though the occasional black sheep would not be out of place. (The all-black breed known as Black Welsh Mountains was developed in the mid-1800s by from selecting and breeding those few black individuals occasionally found in a white flock.) The staple length is 2-4" but can be longer, and the diameter 30-40 microns with coarser kemp. This makes it an ideal medieval "coarse" wool.
Crowfoot, Elizabeth, Frances Pritchard, Kay Staniland. Textiles and Clothing 1150-1450. Boydell Press: 2012.
Icelandic Sheep Breeders of North America http://www.isbona.com/
The Livestock Conservancy http://www.livestockconservancy.org/
North American Mule Sheep Society http://www.mulesheep.com/
Oklahoma State University Department of Animal Science http://www.ansi.okstate.edu/breeds/sheep/
Robson, Deborah and Carol Ekarius. The Fleece & Fiber Sourcebook. Storey Publishing: 2011.
Ryder, M. L. "Medieval Sheep and Wool Types" The Agricultural History Review, Vol. 32 No. 1, 1984, pp. 14-28.
Shetland Sheep Society http://www.shetland-sheep.org.uk/
St. Kilda Soay Sheep Project http://soaysheep.biology.ed.ac.uk/