I don't believe in any absolute standard of morals - there is only what various cultures deem convenient to adopt at various times. Morals cannot be objective because it is easy to concoct moral dilemmas with no unambiguous answer. Like humans, animals also possess morals. For example, for lions, it is customary to devour others' offspring, while among humans it is frowned upon. For ants, sacrificing 100 workers for the sake of the queen is worthwhile, while humans might calculate an analogous situation differently.
Personally, I do what I want, but I operate deterministically, taking into account feelings of justice or fairness as well as fear of punishment, that I acquired through both evolutionary traits and upbringing. For day-to-day life, these instincts serve well enough.
Morals are acquired mostly through evolution via simple negative feedback, for example:
-Murder and theft are bad because you are likely to receive retribution from the victim's friends
-Promiscuity is bad because you are likely to catch a disease or receive retribution from a jealous mate
-Cannibalism s bad because you are likely to catch a prion disease
etc.