2.　Some of the physical differences between human groups are due to differences in hereditary constitution and some to differences in the environments　 in　which　they have been brought up. In most cases, both influences have been at work. The science of genetics suggests that the hereditary differences　 among populations　of　a　single species are the results of the action of two sets of processes.　On　the one hand,　the genetic composition of isolated populations is constantly but gradually being altered by national selection and occasional 　changes　 (mutations)　 in　the　material　particles affected by fortuitous changes in gene frequency and by marriage 　customs.　On　the other hand, crossing is constantly breaking down the differentiations so set　 up.　The new mixed populations, in so far as they, in turn, become isolated, are subject to　 the same processes, and these may lead to further changes. Existing races are merely the result, considered at a particular moment in time, of the total effect of such processes on the human species. The hereditary characters to be used　in　the classification　of human groups, and thus the extent of the　 classificatory　subdivisions　adopted　may legitimately differ according to the scientific purpose in view.

3.　National, religious, geographical, linguistic and cultural groups do not necessarily coincide with racial　groups;　and　the　cultural　traits　of　such　groups　have　no demonstrated connexion with racial traits.　Americans　are　not　a　race,　nor　are Frenchman, nor Germans; nor ipso facto is any other national group.　Muslims and Jews are no more races than are Roman Catholics and Protestants; nor　are　people who live in Iceland or Britain or India,　or who speak English or any other language, or who are culturally Turkish or Chinese and the like, thereby describable　as　races. The use of the term "race" in speaking of such groups may be a serious error, but it is one which is habitually committed.

4.　Human races can be, and　have　been,　classified　in　different ways by different anthropologists. Most of them agree　in　classifying　the　greater　part　of　existing mankind into at least three large units, which may be called major groups (in French grand-races, in German Hauptrassen).　Such　a classification　does　not　depend　on any single physical character, nor does, for example,　skin colour by itself necessarily distinguish one major group 　from 　another.　Furthermore,　so　far　as　it　has　been possible to analyse them,　the differences in physical structure which distinguish one major group from another　 give　 no　support　to　popular　notions　of　any　general "superiority" or "inferiority" which 　are 　sometimes　implied　in　referring　to　these groups.
　Broadly speaking, individuals belonging to different major groups of　 mankind　 are distinguishable by virtue of　their　physical　characters,　but　individual　members,　or small groups, belonging to different races within the same major group are usually not so distinguishable. Even the major groups grade into each other, and　 the　 physical　traits　by　which　they　and　the　races　within　them　are　characterized　overlap considerably.　With respect to most, if not all, measurable characters, the differences among individuals belonging to the same race are greater then the　differences　that occur between the observed averages for two or more races within the　same　major group.

5.　Most anthropologists do not include mental characteristics in their classification of human races. Studies within a single race have shown that　both　innate　capacity and environmental opportunity determine the results of　tests　of　intelligences　and temperament, though their relative importance is disputed.
　When intelligence　 tests,　even non-verbal,　are made on　a group　of　non-literate people, their scores are usually lower than those of more civilized people. It has been recorded that different groups of the same race occupying similarly　high　levels　of civilization may yield considerable differences in intelligence tests.　When, however, similar environments, the differences are usually very slight. Moreover, there is good evidence that, given similar opportunities, the average performance (that　is　to　say, the performance of the individual who is representative because he is surpassed by as many as he surpasses), and the variation round it, do not differ appreciably from one race to another.
　Even those psychologists who claim to　have　found　the　greatest　differences　in intelligence between groups of different racial origin, and have contended　that　they are　hereditary,　always　report　that　some　members　of　the　group　of　inferior performance surpass not merely the lowest ranking member of the superior　 groups, but also the average of its members. In any case,　it has never been possible separate members of two groups on the mental capacity, as they can often be separated on　 a basis of religion, skin colour, hair form language.　It is possible, though　 not　 proved, that same types of innate capacity for　intellectual　and　emotional　　responses　　are commoner in one human group than in another, but it is certain that, within 　a　 single group, innate capacities vary as much as, if not more than, they do between different groups.
　The study of heredity of psychological characteristics is beset with difficulties.　We know that certain mental diseases and defects are transmitted from one generation to the next, but we are less familiar with the part played by heredity in the mental life of normal　 individuals.　The　normal　individual,　irrespective　of　race,　is　essentially educable.　　It follows that his intellectual and moral life is largely conditioned by his training and by his physical and social environment.
　It often happens　that　a 　national　group　may　appear　to　be　characterized　by particular psychological attributes.　The superficial view would be that 　this　due　to race. Scientifically,　however,　we realize that any common psychological attribute is more likely to be due to a common historical and social background,　and 　that　 such attributes may obscure the fact that, within different populations consisting of 　many human types, one will　 find　 approximately　the　same　range　of　temperament　and intelligence.

6.　The scientific material available to us at present does not　 justify　the　conclusion that inherited genetic differences are 　 major　factor　in　producing　the　differences between the cultures and cultural achievements of different peoples of groups. It does indicate, on the contrary, that a major factor in explaining　such　differences　is　the cultural experience which each group has undergone.

7.　There is no evidence for the existence of so-called "pure" races.　Skeletal remains provide the basis of our limited knowledge about earlier 　races.　In　regard　to　race mixture, the evidence points to the fact that human hybridization has been　 going　 on for an indefinite　 but　considerable　time.　Indeed,　one　of　the　processes　of　race formation and race extinction or absorption　 is　 by means of　hybridization　between races.　As there is no reliable evidence that disadvantageous　effects　are　produced thereby,　no biological　 justification 　exists　for　prohibiting　intermarriage　between persons of different races.

8.　We now have to consider the bearing of　these　statements　on　the　problem of human equality.　We wish to emphasize that equality of opportunity and equality in law in no way depend, as ethical principles, upon the assertion that human beings are in fact equal in endowment.

9.　We have thought it worth while to set out in a formal manner what is　at　present scientifically established concerning individual and group differences.

　(a)In matters of race,　the only characteristics which anthropologists have　so　far been able to use effectively as a basis for classification are physical　(anatomical and physiological).

　(b) Available scientific knowledge provides no basis for believing that the groups of mankind differ in their 　innate 　capacity 　for 　intellectual 　and 　emotional development.

　(c) Some biological differences between human beings within a single race　may　be as great as, or greater than, the same biological differences between races.

　(d) Vast social changes have occurred that have not been connected in any way with changes in racial type.　Historical and sociological studies thus support the　view that genetic differences are of little significance in　determining　the　social　and cultural differences between different groups of man.

　(e) There is no evidence that race mixture produces disadvantageous results from a biological point of view. The social results of race mixture, whether for good or ill, can generally be traced to social factors.

(Text drafted, at Unesco House, Paris, on　8　June　1951,　by:　Professor R. A. M. Bergman, Royal　Tropical　Institute,　Amsterdam;　Professor　Gunner　Dahlbelg, Director, State Institute for Human Genetics　and　Race　Biology,　University　of Uppsala; Professor L. C. Dunn, Department of Zoology, Columbia University, New York; Professor J. B. S. Haldane, Head, Department of Biometry, University College, London; Professer M.F. Ashley Montagu, Chairman, Department of Anthropology, Rutgers University, New Brumswick, N.J.　;　Dr. A. E.　Mourant,　Director　Blood Group Reference Laboratory, Lister Institute, London; Professor Hns　Nachtscheim, Director, Institute fur Genetik, Freie Universitat,　Berlin　;　Dr. Eugene　Schreider, Directeur adjoint du Laboratoire d'Anthropologie Physicure de l'Ecole des Hautes Etudes, Paris; Professor Harry L. Shapino, Chairman, Department of Anthropology, American Museum of Natural History,　New York;　Dr. J. C. Trevor,　Faculty　of Archaeology and Anthropology,　University of Cambridge:　Dr. Henri V. Vallois, Professeur au Museum d'Histoire Naturelle, Directeur du Musee de l'Homme, Paris; Professor S. Zuckerman, Head, Depertment of Anatomy, Medical School, University of Birmingham; Professor Th. Dobzhansky, Depertment of Zoology, Columbia University, New York, and Dr. Julian Huxley contributed to the final wording.)