Old World camels in a modern world - a balancing act between conservation and genetic improvement

Abstract

Old World camels have served humans in cross-continental caravans, transporting people and goods, connecting different cultures and providing milk, meat, wool and draught since their domestication around 3000-6000 years ago. In a world of modern transport and fast connectivity, these beasts of burden seem to be out-dated. However, a growing demand for sustainable milk and meat production, especially in countries affected by climate change and increasing desertification, brings dromedaries (Camelus dromedarius) and Bactrian camels (Camelus bactrianus) back onstage and into the focus of animal breeders and scientists. In this review on the molecular genetics of these economically important species we give an overview about the evolutionary history, domestication and dispersal of Old World camels, whereas highlighting the need for conservation of wild two-humped camels (Camelus ferus) as an evolutionarily unique and highly endangered species. We provide cutting-edge information on the current molecular resources and on-going sequencing projects. We cannot emphasise enough the importance of balancing the need for improving camel production traits with maintaining the genetic diversity in two domestic species with specific physiological adaptation to a desert environment.

Keywords: Bactrian camel; domestication; dromedary; evolutionary history.

Figure 1

Migration map of the historical camelid family. The current distribution of dromedaries and Bactrian camels is presented in red and green colours. The last refugia of the wild two‐humped camels in China and Mongolia are shown as dark‐green patches. The map was adapted from Mesa Schumacher/AramcoWorld (https://www.aramcoworld.com/en-US/Articles/November-2018/The-Magnificent-Migration). Reprint permits were granted by AramcoWorld on March 6, 2019.

Figure 2

Mitochondrial DNA neighbour joining network of ancient (red) and modern (grey) dromedary samples. Wild extinct dromedary samples are marked with an asterisk. The geographical origin of the archaeological specimen is shown in Fig. 3. Reprinted from Supplementary Material of Almathen et al. (2016).

Figure 3

Schematic representation of the historical network of caravan routes (i.e. Incense and Silk routes) according to descriptions from Bulliet (1975) and Heiss (2012). The historical repartition of domestic dromedaries is depicted with dashed lines. Archaeological sites of the ancient specimens used for phylogeographic analyses (Fig. 2) are shown with black stars. Solid lines show the human‐driven camel migration along historic caravan routes: (i) from the Gulf of Aden to the North Arabian Peninsula as part of the Incense Road; (ii) the trans‐Saharan route; and (iii) the Silk Road, which bordered the Mediterranean coast and connected northwestern Africa to the north of the Arabian Peninsula from where caravans departed for southern Asia. The most contemporary migration route started in the 1860s and linked Pakistan to Australia, where several thousand camels were imported. Reprinted from Supplementary Material of Almathen et al. (2016).

Figure 4

Camel types. (a) Camel hybrid F1 (Bactrian camel × dromedary) used for camel wrestling, a traditional event in Turkey. (b) Arvana dromedary in Turkmenistan. (c) Al‐Homor dromedary in Saudi Arabia. (d) Racing camel Al‐Hurra in Saudi Arabia. (e) Mongolian Bactrian camel with its high‐quality fur. Photo credits: Bernard Faye.