“If you could compare yourself with any animal, which would it be and why?”
Apparently this is a common odd-ball question at job interviews. I like to think I am goat. Curious, independent, playful and highly adaptable. You would have pictured something entirely different if I had said I was a sheep. Soft and fluffy? A mindless follower? Anxious?
But is there really that much of a difference between a goat and a sheep?
They are both relatively small-sized ruminants that bleat. Both are often white. In reality, sheep and goats bring different things to the table – literally. There are differences in the quality of their meat. Although sheep milk is fattier, goats tend to produce milk in larger quantities. Sheep obviously give us wool but goats are also useful. For example, they have been used by Pastoralist people in Africa as a defense against tsetse flies: they eat the vegetation, destroying the flies’ habitat.
So what is the quickest way to distinguish the domestic goat (Capra hircus) from the domestic sheep (Ovis aries)?
Goats have horns? Wrong, some sheep also have horns!
Goats have beards? Also wrong, not all goats are equally handsome.
It’s all in the tail! The tail of a goat points up, and sheep have hanging tails. Differences between the two taxa are elegantly portrayed in the infographic below:
But not for an archeologist… Many of these differences are in the soft tissues or behaviors and thus do not preserve in time. As a result, archeologists often lump together bones or fossils from goats and sheep because they cannot distinguish them. Goats and sheep were both domesticated in the Fertile Crescent region in the Near East and Mediterranean during the Early Neolithic and their remains are often found together at sites from this period. There are some differences in their bone morphology, but they are very subtle to the non-expert and not always reliable.
Another confounding factor is that the evolution of these animals was highly influenced by selection of desired traits by humans (artificial selection for early sexual maturity, coat color, smaller horns). There are also multiple species of wild goats and sheep which further complicate the family portrait.
There’s one way sheep and goats are clearly different: genetics. Sheep have 54 chromosomes, and goats have 60. In the last 15 years or so, genetics studies have become increasingly popular and started tackling archeological questions. Some have looked at the early domestication of various animals, including the bleaters in question. Genetic studies have not only allowed us to distinguish between the archeological remains of a goat and a sheep, but they have also provided significant insights into the speciation of each taxa. At least 6 mtDNA haplogroups (or genetics “types”) of domestic goats have been found, which would correspond to multiple domestication events. Similarly, at least 5 sheep haplogroups have been found. Although it’s worth pointing out that DNA is just a useful tool – not magic. DNA, and particularly ancient DNA, can suffer from contamination at the site, the lab or anywhere in between.
But generally speaking, if you’re a goat and someone mistakes you for a sheep, don’t worry, just request a DNA test!
For more on sheep and goat genetics:
Luikart, Gordon, et al. Multiple maternal origins and weak phylogeographic structure in domestic goats. Proceedings of the National Academy of Sciences 98.10 (2001): 5927-5932.
Meadows, Jennifer RS, et al. Five ovine mitochondrial lineages identified from sheep breeds of the near East. Genetics, 175.3 (2007): 1371-1379.
To learn how archeologists differentiate the two animals:
Zeder, Melinda A. (2010). Assessing the reliability of criteria used to identify postcranial bones in sheep, Ovis, and goats, Capra. Journal of archaeological science, 37 (11), p. 2887 – 2905.