First of all, eating, sleeping, mating and defending are things that all animals do, so human life's goal can't be any of those. There are people that strive for money to just get one or more of above, or some other materials, that are short-living; so earning money can't be it either. What I mean by short-living is that human life span can be small or large depending on perspective changes, but if one looks at other things from the perspective of life's length, then life outlives them. So, in toto, they're short-lived).
Modern science discovers (as against invents!) various things that are considered to give comfort and progress in lots of areas of living. But any peek at scientific history would show that even earlier theories discovered are refuted and replaced by new findings! So although it may be called as progress, it is impermanent and hence not the aim. Some parts of science may well be roads that lead to the aim gradually, but not the purpose.
Some people consider their love to be the whole and sole purpose for themselves, be it towards anyone. Consider this love of theirs fails for reasons like anger, jealousy, etc, even for fractions of time. During that period of failure, it gives a miserable feeling and that shows the transient nature of love too! Ofcourse, things like selfless love are pure and don't have any dependency on failures, but that is only a means, not the end goal. Similarly, bhakti, all sorts of yogas, etc, are just mechanisms to purify and ready one towards the goal but as they're means, they can't be held on for ever.
Consider another case as given in tripuraa rahasya: A man enjoys the union with his wife, but the latter doesn't. For him, it seems like making love to a piece of wood! On enquiring, she tells him that whatever gives him pleasure can't give her pleasure, since she knows it to vary from person to person and that it is impermanent. Even what the husband is considering as the greatest pleasure, he is not so happy about it due to his wife's indifferent behaviour during the union. She then narrates to him a set of stories due to which he gets a feeling of disgust and realizes that all pleasure in worldly things is derived temporarily!
Wondering why I'm saying that such-and-such is not a goal as against such-and-such is the goal? Well, its because the end is something that cannot be defined in terms of its qualities, characteristics, or what it is. It can only be defined by saying what it is not. To quote Sherlock Holmes, "When you have eliminated the impossible, whatever remains, however improbable, must be the truth". That is quite true in life, while searching for an answer. Anything that is impermanent can't be true, so it has to be discarded. Cling onto something thats true. Thats the neti-neti principle of advaita. Everything in life needs to be analyzed from the objective of investigation and then discarded based on the substratum behind the thing analyzed, which is truth for that analysis. Then take the next case and go on to find the substratum behind that result, and so on, till the Ultimate Truth is *realized*. That would be the purpose of life, the sole aim, the goal, the permanent, the existence-consciousness-bliss, the brahmaN.
om tat sat