Are We All Basically Trying To Mate Efficiently?

If you have not already guessed the book I am refering to, 'The Mating Mind' by Geofferey Miller is sort of a revelation, at least theoretically.

An excerpt
"Traditionally, evolutionary theory has explained intelligence as merely a by-product of surplus brain size. But psychologist Geoffrey Miller argues that it actively evolved, like the peacock's tail, for courtship and mating, and thereby shaped human nature.Miller maintains that both human sexes have evolved significant ways of displaying fitness via expression of creative intelligence such as storeytelling, poetry, art, music, sports, dance, humor, kindness, and leadership."

Intelligence is the root "cause" all questioning, imagination, speculation and creation. Its the reason why we can think and talk about conciousnessness, soul and God. Its the basis of self-realisation.

What if all this was simply an evolutionary strategy to attract better mates and thus multiply further into better life forms? (As senseless or sensible as a dogs' evolved ability to sniff, which even by the farthest stretch of imagination, doesnt seem to be affecting the workings of the universe in any way.)
Procreation, is probably the only universally acceptable reason for existence. Simply because death itself is such a stark reality. (I am rather extreme in wondering that "what end purpose does existence itself serve?". Thats deserves a different post.)

All creative activities that human beings indulge in seem quiet unnecessary for survival. Poetry, music, writing, painting.. all art forms, are not naturally adding to making the survival easier. (On the contrary it makes it tougher sometimes, for eg. when you ponder upon the reason of your existence real hard and feel frustrated at not having an answere.)

So are all the creative and intellectual faculties basically directed towards becoming a more suitable potential mate? If it is false, then fine. If its true, then doesnt it undermine the importance of all thought processes that are essentially creative? Doesnt the world seem fabricated? Can survival and procreation actually be the core principles driving the entire machinery of the cosmos?

PS. A rather weak argument that I could think against his theory is as follows. Its interesting to note that the brain (not necessarily mind) is a constituent of ALL organisms. A peacock's feathers (or featehrs in general), on the other hand, are not present across all animals. That gives brain a different status, and therefore weakens Geoffrey's hypothesis.
Also, I would like to know of more animals with an evolutionary drift specifically towards sexual selection. What is a dog's tool? (not that!). Or how do pigeons figure who is a better mate? Isnt everything in the body (and in the human case, mind) leading towards the decision of a better mate, so why the emphasis on intelligence?