While I hold the Pāli Canon as authentic it is not without some corruption. It is important to bear in mind that the material was transmitted orally for hundreds of years before beings set to text. Even in the Buddha's time there was a "counterfeit dhamma" circulating (see SN 13:16) and being taught. It would be unreasonable to believe that there are no flaws in the Pāli literature. It is my personal opinion that the majority of these flaws are found within the Digha Nikāya. There is a theory circulating among academics that this text was designed to bring new prospects into the Sangha (see Joy Manné's "Categories of Sutta in the Pali Nikayas and Their Implications for Our Appreciation of the Buddhist Teaching and Literature," Journal of the Pali Text Society 15 (1990): 29-87.) If this were true it would make sense that this volume would make reference to some of the prevailing Vedic beliefs of the time, particularly those that outline cosmology. The "32 marks of a great man" would possibly be another example. If these were meant to be a physical description of the Buddha one would have to ask why King Ajattasatu was unable to pick the Buddha out of the crowd as he looked like any other monk (DN 2).
Despite whatever flaws the Pāli literature may contain these texts are the closest thing we have to the Buddha's actual words.