Biological cohesion
The ecological niche can be defined as: the environmental conditions and resources necessary to a normal development of a population.  It has been used in a number of ways in anthropology: as a specialised part of human society, as synonymous with culture, and as a segment of the habitat.  It is actually the multi- dimensional concept of the human ecological niche which renders the niche idea of greater value to studies of human ecology.  The importance of biological factors is stressed, and particular attention is paid to the principle of competitive exclusion, to human niche specialisation and to Cohen's criteria of huiman adaptive success.
This ecological niche concept was developed by Hutchinson, and it was entitled as multidimensional or Hutchinsonian niche. The multidimensional niche concept is one of the most adequate tools to study interactions between man and its surrounding environment. The utility of ecological niche concept, applied to the man, was firstly discussed and systematized by Hardesty and has been useful to understand the use of natural resources by human populations.
The use of ecological niche concept has allowed evaluating the food resources dependence degree and seasonal variations on a diet of a person, families or communities of local social groups. This approach also allows establishing important relations among the analysis units, which diet may differ depending on social, economical and cultural factors, or on the distinctive ways of using resources.
One of the striking facts about contemporary society, and indeed of much of recorded history, is the division of the human species into distinct ethnic groups, whose interrelations are sometimes antagonistic and sometimes mutualistic.  While there are many interesting ways that social scientists are analysing this phenomenon, ecological theory may provide some additional insights.
One of the most important ecological aspect relevant to biological cohesion is that human beings are biologically adapted for culture in ways that other primates are not, as evidenced most clearly by the fact that only human cultural traditions accumulate modifications over historical time (the ratchet effect). The key adaptation is one that enables individuals to understand other individuals as intentional agents like the self. This species-unique form of social cognition emerges in human ontogeny at approximately 1 year of age, as infants begin to engage with other persons in various kinds of joint attentional activities involving gaze following, social referencing, and gestural communication. Young children's joint attentional skills then engender some uniquely powerful forms of cultural learning, enabling the acquisition of language, discourse skills, tool-use practices, and other conventional activities. These novel forms of cultural learning allow human beings to, in effect, pool their cognitive resources both contemporaneously and over historical time in ways that are unique in the animal kingdom.