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RESEARCH PRODUCT

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Let us sit on the terrace of a street cafe and watch the crowds pass by. The first basic unit we observe is the individual: tall, small, fat, long-faced, round-faced — the diversity is large. Among these individuals there will be a few with particular features, such as colour of skin or type of hair, which differ from the vast majority of local individuals, thereby indicating that they originated from another part of the world. We shall install a video camera at this site and will carry out the same observations simultaneously in Paris, Dakar, and Tokyo. When the films are then brought together and shown in the same room, the observers will not fail to note that the individuals of one city have certain dominant characteristic which set them apart from the individuals of the other cities, there is thus a group of individuals who have similar features and constitute a local population. However, despite the particular features characterizing the local population, the various individuals will show a much larger number of common features. Furthermore, they may mix, as shown by couples where the two individuals are from different populations; the children accompanying such couples are proof of their fecundity. The large number of shared common features, and especially the fecundity of these combinations, show that the various individuals belong to the same species.