Although it is occupying quantitavely a marginal place among the domestic herbivorous (0.4% only of the world domestic herbivorous), the large camelids (dromedary and Bactrian) are present in almost all the arid lands of the old world (except in Southern Africa), wide spread over 35 millions km². They are overall remarkable enhancer of these spaces by their productive potential and by their role in the agro-ecosystemic balance of the arid lands, especially with the current climatic changes. Elsewhere, they are known for their physiological peculiarities linked to their adaptation ability to harsh conditions of the desert and of its margin. In consequence, they represent a fabulous biological model for the scientists from different disciplines. Their place in the "modern world" has to be re-evaluated by considering these trends and these particularities.