All purposes we humans have are of our own making. As far as we know, there is no other species which can think of a purpose of, say, something to do next week.Quote
How can you fulfil a purpose unless you know what it is?
Is there a definite purpose of things is or is it something you invent for yourself?
All species behave in a way which enables them to survive. If they do not happen, by natural or random means, to have acquired a behaviour which means they are able to survive a change in conditions, then that species becomes extinct.