Friday mystery object #138 answer

On Friday I gave you this object to identify:

The idea was to provide a sense of how tricky it can be to identify bits of postcranial bone, even fairly characteristic bits like the humerus (which is what this is).

There were various suggestions, with sheep, goat and deer all getting a mention, but henstridgesj and Jake both got the same identification as the collector when they suggested Domestic Pig Sus scrofa domesticus Erxleben, 1777.

Now you may wonder why I’m being slightly circumspect about whether that answer is actually correct – so I will give you my thoughts.

Erith Marshes are (rapidly becoming ‘were’) an area of grazing land by the Thames on the East side of London. Various domestic animals would have been reared there, so a variety of options present themselves.

Narrowing it down can be done by looking at size and shape. In respect to this Jake said:

This one is 17cm. I have a 8 month old red deer hind humerus which is about 20cm, so it is too [small] to be red but the proportions are right. I have a young roe deer one which is about 16cm but roe is much thinner. So I am going to stick with deer but say axis or sika.

This is useful, because it introduces the idea of robustness of the bone as well as the length. This bone is too short for a Red Deer, but too robust to be Roe Deer. Other options might indeed be Sika or Axis, but given the locality that seems unlikley. So what other options are there?

Sheep, Goats and Pigs are all in the right size range and given the nature of the Erith Marshes they may all have been present in the late 1950’s. To distinguish which we have here then falls to morphology – which is somewhat hampered by the fact that bits of this bone have been damaged.

UCL Boneview provides us with a helpful resource here:

From this image it looks like the most similar bone is in fact the Ovis/Capra (Sheep/Goat) humerus, although it looks relatively longer and thinner than the mystery object. The Sus (Pig) humerus looks far more robust, with a much larger area for muscle attachment.

This robustness in the pig is a bit of a problem for identification, because pigs vary in body mass considerably depending on the breed and how the Pig is reared. This means that the amount of force being transferred through the bones of each individual Pig will vary a lot – which will influence how robust the bone becomes.

Of course the same can be said for Sheep and Goats, although their body mass doesn’t vary anywhere near as much as that of Pigs, so unless the bone from Erith is from a very chunky and squat Sheep it probably is from a lightweight Pig. I’m still not 100% certain which it is, but I think the Pig is a little bit more likely.

Such uncertainties are most unsatisfying, but they are all too common and it’s better to acknowledge them than labour under unfounded certainty.

6 thoughts on “Friday mystery object #138 answer

  1. This was a great lesson on morphology. I didn’t realize how much a skeletal element can be affected by breed or lifestyle. Post cranial FMOs are a lot of fun. They’re my favorite challenges here because of all the discussions and comparisons in morphology and how related animals are. Thanks, Paolo! And congrats to the henstridgesj and Jake for another week solved!

  2. Hmmm. Late 1950s, grazing land in south east England. A couple of counties further north, growing up on a farm, I never saw free ranging pigs. They were too valuable. Robust sheep, yes, plenty of those.

  3. Considering the morphology of the proximal end and the trochlea, I’d say it’s not pig, but sheep. The pig trochlea is more uneven in size and lacks the lateralmost little end that sheep has. Also, I can’t see it in this picture, but the distal third of the shaft in pig has a strong slant, whereas the sheep is more round/square. As for the proximal end, if you compare not only the anterior view in the UCL link but the proximal one, you can see that the pig humerus looks very different from your specimen. Differences in species size and robusticity can make bone identification difficult, but there are usually very little differences in general morphology in animals from the same species.

    I think therefore that this is a case of mis-identification in the original records.

    • Thanks Lena, I think you could be right about the misidentification and I spent quite a considerable time wavering between Pig and Sheep when writing the answer. The trochlea difference in particular had me thinking it was Sheep. However, I have seen humeri of young Pigs that are much more Sheep-like than humeri of adult Pigs. I will take your observations on board and consider them when I next look at the specimen – there is nothing like having specimens to hand when faced with an equivocal identification!

  4. Pingback: Friday mystery object #143 answer « Zygoma

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