Mill's View of Lower/Higher Pleasures

Mill is a utilitarian philosopher who lives by the Greatest Happiness Principle, in which there is a clear distinction between both lower and higher pleasures. Though thoroughly explained, one must also question the justification of these pleasures. Many of these beliefs leave the reader hanging on the edge, with further questions that need to be answered. What is the exact distinction between the lower and higher pleasures? And how are higher pleasures measured as most valuable? How clearly is Mill’s view of lower and higher pleasures justified?
Mill, unlike some utilitarians (Epicureans), believes that there is an immense distinction between higher and lower pleasures. Lower pleasures, according to Mill, are those based off of sensations. “Few human creatures would consent to be changed into an of the lower animals for a promise of the fullest allowance of a beast’s pleasures…” (Mill, Self-Love 506) Both humans and animals are capable of experiencing these pleasures, but what Mill believes is that only Humans are capable of the higher pleasures, and therefore no intelligent human being would chose to become an animal incapable of these more valuable pleasures. The lower pleasures are based off of sensations in which include things such as our five senses: taste, hearing, touch, sight and the sense of smell. One will experience these pleasures multiple times daily, thus reducing the amount of satisfaction one feels when experiencing a lower pleasure. Mill believes that animals and human beings both share similar experiences when it comes to the lower pleasures, but that only human beings are capable of the higher pleasures. How one measures the justification of the distinction between the lower pleasures and the higher pleasures is based mostly on opinion. It does make sense that since human beings are most definitely superior in the intellectual field that in order to achieve a greater value of happiness one must experience the higher pleasures, but