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Domestication begins with the selection of animals showing less fear of humans. In most domesticates, selection signals for tameness have been superimposed by intensive breeding for economical or other desirable traits. Old World camels, conversely, have maintained high genetic variation and lack secondary bottlenecks associated with breed development. By re-sequencing multiple genomes from dromedaries, Bactrian camels, and their endangered wild relatives, here we show that positive selection for candidate genes underlying traits collectively referred to as ‘domestication syndrome’ is consistent with neural crest deficiencies and altered thyroid hormone-based signaling. Comparing our results with other domestic species, we postulate that the core set of domestication genes is considerably smaller than the pan-domestication set – and overlapping genes are likely a result of chance and redundancy. These results, along with the extensive genomic resources provided, are an important contribution to understanding the evolutionary history of camels and the genomic features of their domestication., Robert R. Fitak et al. investigate the genetic basis for domestication in camels. They found that the positive selection of candidate domestication genes is consistent with neural crest deficiencies and altered thyroid hormone-based signaling. Their work provides insights to the evolutionary history of camels and genetics of domestication.

At world level, the current official number of large camelids cannot be determined exactly (it is estimated to be more than 35 million heads), and the role of camels in the livestock economy is highly variable. The only reliable statistics are provided by FAO since 1961. According to these data, five different patterns of demographic changes have been observed. In countries marked by a regular or drastic decline of their camelid population, a tendency to re-increase has been in force since the beginning of the century, except in India. Generally, countries marked by a sharp recent increase in their large camelid population have implemented a census and readjusted their data. Many inconsistencies occur in available data, most notably cases arising from changes occurring in state status (for example secession of Eritrea, Soviet Union collapse). Moreover, large camelid stocks in Australia, in countries of new camel establishment (Western countries) and those related to the expansion of camel farming, notably in Africa, are not recorded in the international database. In addition, there is no distinction between dromedary and Bactrian data. The present large camelid population in the world is probably more than 40 million and could reach 60 million after 25 years from now if the current demographic trend is maintained.