Inherently individual

Its a long way from fish to men but I suspect that the same would be true for man if ethics did not prevent the same experiment on humans. From Behavioural individuality in clonal fish arises despite near-identical rearing conditions by David Bierbach, Kate L. Laskowski & Max Wolf.

Behavioural individuality is thought to be caused by differences in genes and/or environmental conditions. Therefore, if these sources of variation are removed, individuals are predicted to develop similar phenotypes lacking repeatable individual variation. Moreover, even among genetically identical individuals, direct social interactions are predicted to be a powerful factor shaping the development of individuality. We use tightly controlled ontogenetic experiments with clonal fish, the Amazon molly (Poecilia formosa), to test whether near-identical rearing conditions and lack of social contact dampen individuality. In sharp contrast to our predictions, we find that (i) substantial individual variation in behaviour emerges among genetically identical individuals isolated directly after birth into highly standardized environments and (ii) increasing levels of social experience during ontogeny do not affect levels of individual behavioural variation. In contrast to the current research paradigm, which focuses on genes and/or environmental drivers, our findings suggest that individuality might be an inevitable and potentially unpredictable outcome of development.

Humans are a product of a complex, dynamic, multi-causal, chaotic system. Controlling for environment and controlling for genes is insufficient to produce identical outcomes. People will be differentiated individuals. The system is too complex for it to be otherwise.