The old nature vs. nurture argument. Honestly, to me this is a bit of a misnomer. It implies that one is dominant over the other. In truth, there is a feedback mechanism. Your genes direct certain chemical processes which are triggered by your environment. Of course similar genetic make up would cause similar chemical responses, which in turn would provide a strong weighting factor for similar behaviors. An article I read recently said that introvert and extrovert brains are physically wired different. A recent article David posted talked about the role of cells guiding/generating the brain map. So it stands to reason that genetically identical individuals would have brains that were wired similarly, which would give a strong tendency to introversion/extroversion and the associated characteristics. If you follow the work of Carl Jung, you would know that one change alone cuts the number of personality types in half. However, this study demonstrates that even with all those changes, even with so many similarities, there is still personality variation. (something we already knew). Other studies show that stress/joy actually changes body chemistry, which we know changes how certain things are expressed.So, combined, they actually answer the question: nature informs nurture informs nature etc.

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What is the purpose of living? How about, 'to reduce needless suffering. It seems to me to be a worthy purpose.

George (under “Evolution: a different view”): This article reports research which suggests that variation within populations may itself be written in the genes, not just reactions against environmental changes.-https://www.quantamagazine.org/20150512-fruit-flies-individuality/?utm_source=Quanta+Ma...-dhw: The only thing that surprises me in this article is the fact that scientists themselves seem surprised that individual organisms behave differently. Yet again it is the arrogance of humans to assume that the less an organism looks like us, the more we can regard it as an automaton. 
The authors try to trace differences to genetic factors. The article has nothing to do with innovation in evolution, and everything to do with behaviour - and exactly the same arguments could be applied to humans. To what extent is our behaviour regulated by our genes? THAT is the burning question, and so I'm putting it on a different thread.-DAVID: Identical twin studies when separated and raised apart strongly support the proposal that they inherit very similar attitudes in the way they conduct their lives.-Thank you. This suggests that those attitudes are regulated by the genes. But the article is very confusing on this issue:-QUOTE: "The animals' behavior varied much more than he expected, even when the flies were more or less genetically identical and raised under the same conditions. “If you hold genetics constant and the environment mostly constant, you still see a lot of variation,” de Bivort said.-QUOTE: By comparing soldier and dancer strains, de Bivort thinks he's identified both a gene and a neural circuit that may underlie some of these differences."
-“Some of these differences” leaves plenty of leeway, and so does “more or less genetically identical”, but the second quote implies that individuality IS caused by the genes, and the first that it is not.-The whole subject is very rich. I have repeated my first comment, as it is a clear rebuttal of your own beliefs, David, that the so-called lower forms of life (bacteria, insects) are automatons. The rest raises the old and never resolved question of free will. If flies make different choices when confronted with the same options, one is tempted to say they have free will. But if their individual decisions are governed by their individual genes, they are individually preprogrammed to act the way they do. Why should not the same argument apply to humans?