Thursday, May 19, 2016

A Brief History Camels (And Humans)

Fig.1. Dromedaries in Israel (Credit: Wilson, 2011)

For the past 3,000 years, single-humped camels, known as dromedaries (Camelus dromedarius), have provided an important source of food and transport to desert communities. The origin of the domesticated dromedary, however, remains relatively unknown. A recent article published in the journal Proceedings of the National Academy of Sciences, reveals some clues as to where and when humans started to depend upon these animals.

An international team led by researchers at the University of Nottingham, the University of Veterinary Medicine in Vienna, and King Faisal University in Saudi Arabia analyzed genetic information from nearly 1,100 living dromedaries from 21 countries. They also went back in time with bone samples from early-domesticated animals dating between 400 to 1870 AD and even earlier with wild samples from 5,000 to 1,000 BC. A comparison of the ancient and modern genetic material suggested the dromedaries were probably domesticated in the Southeast Arabian Peninsula.

In addition to geographic information, the DNA analyses revealed a surprising amount of genetic diversity among the modern dromedary populations.  During domestication, both animal and plant populations usually lose genetic diversity overall as farmers breed for desirable traits. The researchers, however, found that dromedaries were very different from other domesticated animals.

The team determined that the high genetic diversity comes from the animal’s role as a transport animal over thousands of years. Caravans moving across great distances bring new populations of dromedaries in contact with one another, allowing for regular gene flow. The study revealed that only one population in East Africa had comparatively low diversity and was probably isolated through time, due to geography or cultural barriers.

Human migration and trade may have shaped dromedary diversity, but their adaptation to arid environments make them essential for people today living in what the authors call "marginal agro-ecological zones." These animals can survive for weeks without water and withstand scorching temperatures. Additionally, scientists are also interested in their roles as a natural reservoir for deadly pathogens, such as the Middle East Respiratory Syndrome (MERS) coronavirus.

Time and time again, ancient and modern samples show that understanding the evolutionary history of a species is essential to address modern concerns, such as tracing the development of maize or mapping biodiversity. This dromedary study certainly reveals a unique relationship between human movement and a domesticated animal, but it also holds lessons for future ecological and food security challenges.


References
Almathen, F., et al. (2016, May 09). Ancient and modern DNA reveal dynamics of domestication and cross-continental dispersal of the dromedary. PNAS. Doi: 10.1073/pnas.1519508113

Arabian (Dromedary) Camel. [n.d.] National Geographic. Retrieved from http://animals.nationalgeographic.com/animals/mammals/dromedary-camel/


Glossary

gene flow
Also called “migration” or “gene migration,” this is any transfer of genetic information from one population to another.

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