The person it is proud calls himself "the tsar of the nature", but on many indicators he fairly concedes to other animals. First of all, it belongs to sense of smell.
From all feelings inherent in the person, the sense of smell should be put on the last place. Sometimes it saves to people life – helps to find leak of gas in time or to reject stale food – and still loss of sense of smell does not do the person by such heavy disabled person as loss of hearing or sight. People often face temporary loss of sense of smell, having cold, and it is transferred quite easily. Such small part of sense of smell in human life is connected with its weakness: it cannot be of great importance as gives not enough information on the world.
Easing of sense of smell happened according to fundamental laws evolutions: the sign which stopped being critical for survival and leaving of posterity was not maintained by natural selection. In origin of the person the big role was played by transition to meat food, but it occurred not at once: long enough ancient primacies were "vegetarians". By search of fruits among foliage the sight plays more significant role, than sense of smell, and visually impaired individuals had much more chances to die from hunger, without having left posterity, than at individuals with a bad scent. But in order that a certain sign was fixed, insufficiently, that it was not harmful – it is necessary that it brought some benefit.
The solution lies in a way of life ancient a hominid. Once scientists built idea of it on the example of the animal, closest to the person, – a chimpanzee. Promiscuity is inherent in these monkeys: any female in pack can copulate with any male, and only the hierarchy of males somehow orders this process, high-rank individuals get more "girlfriends", than low-rank. Further researches of fossil primacies – in particular, Ardis – forced to introduce amendments in this picture.
At males of monkeys in whom promiscuity is inherent the canines are much larger, than – they in literal sense "win" from females to themselves the right for reproduction. At the person and his fossil ancestors of such line is not present, and it forced the American anthropologist O. Lavdzhoya to assume that ancestors of the person ensured reproductive success in a different way – creating constant couples.
The strategy of a monogamy is peculiar to only 5% of mammals, and the principle "sex in exchange for food" is the cornerstone of it. The leading role when choosing the partner belongs to the one who puts more resources in posterity – at primacies it is females, and in such conditions those males who feed "ladies" better have the greatest chances. In this sense the males deprived of good sense of smell owing to mutations were out of competition.
The female receives the greatest number of food from a male those days when she is most attractive to it – during an ovulation, and in other time he can not be interested in a female at all and not to feed her. Males determine approach of such days by a smell, instinctively reacting to its change. If the male differed in weak sense of smell, change of a smell did not matter for it, he showed interest in a female and fed her constantly. Such "gentlemen" were pleasant to "ladies" more and, respectively, had more chances to leave posterity. Easing the sense of smell is the price which evolutionary ancestors of the person paid for the strategy of survival of a look.