Are we born to an evolutionary purpose?

Well there is in the sense that evolutionary explanations attempt to provide a deeper understanding. An understanding based on origins of behaviour in terms of ancestral environment and gene propagation. Goddidit just begs the unanswerable question as to WHY Goddidit. It provides no understanding whatsoever as to why we are the way we are.Understanding human nature (whether we accept certain aspects of that nature as undesirable in modern society or not), it's origins, the environment it developed in and the differences our current environment requires of us, must be an important step in looking at "what do WE do next"?Edited by Straggler, : No reason given.

I also question the validity of looking for an answer for every sort of inividual human behaviour. Given the complexity of the subjects involved (i.e. us)it would seem to be pointless task doomed to error and failure.
Maybe your sister should investigate her need for such answers...........However broader tendancies do seem to have genetic foundations. There may not be a "murder gene" but there may be a genetically related tendancy to aggression and violence which will make some individuals in some environments more likely to commit murder than others.I don't think science claims to tell us what we should or shouldn't do. It merely provides us with the knowledge on which we can make those decisions if we choose to make them.
Would you stop studying human behaviour scientifically because you might not like the results?
Goddidit provides us with nothing except perhaps false reassurance.

It is true that natural = good is a common misconception in this sort of area. However this does not mean that becuase something is "'meant' to be that way" (as you put it) we have to accept it as morally right or socially acceptable.Just because humans have a natural inclination to fatty sugary foods due to an ancetral environmnet where these sources of energy were relatively scarce does not mean it is good to pander to these inclinations.The same is even more true of rape, murder etc. should these be found to have an overriding "natural" basis.We may need to factor in human nature in making such decisions but claiming natural (in whatever sense) necessarily equates to right or even desirable is just silly.

In my view neither irrational religious convictions nor demonstrations of what is "natural" alone should define what we decide is right, wrong, desirable or advantageous in modern society. We are intelligent enough (hopefully) to come up with better and more inclusive methods of deciding those things.However understanding human nature may well guide us as to the extent to which it is possible in practice to construct reasonable laws and moral coes that we, as a species, are actually able to follow.In my view people should be free to do what they choose as long as they are not harming anyone else. That applies as much to homosexuality as it does to a preference for red wine over white. Regardless of either preference being due to genetic, cultural or a combination of the two reasons.Outlawing sexual relationships that hurt nobody is going to be a stupid law if the need and desire for mutually satisfying sexual relationships is so ingrained in human nature as to be effectively impossible to nullify on any realistic scale.Whether homosexuality is due to biology or not does not make it right or wrong. However if homosexuality is so ingrained in human nature as to be inevitable then any morality that excludes homosexual practices would seem to be doomed to conflict, hypocrisy and eventual failure. Thus making it a foolish and bad code of morality.As a counter example consider rape. If rape is natural does that make it right? A law system and moral code that protects people from being the victims of rape, regadless of how 'natural' or otherwise rape may be found to be is one that places the rights of the innocent individual above the natural urges of the rapist and is a perfectly viable code of morality. It may well not eradicate rape but it should reduce it through stigmatisation and punishment of rapists.Edited by Straggler, : No reason given.