Sure, religions have been the major force driving morality over the last few thousand years, and are largely to credit for enabling us to self organise into large civilisations in the first place, but they evolved on the back of an entire history of human thought that must be considered.  Secular moral philosophy has also played a large part, particularly since the enlightenment.

Religions have provided the philosophical framework for morality, metaphysics and [generally flawed] epistemology in all civilisations of history.  However, civilisations as we know them only go back 10,000 years or so (and only 3000 years for those based around the great monotheistic religions I assume you are talking about).  Previous to that, when we lived in small tribes, we would presumably have had beliefs much like those found in remote tribes today, far less structured belief systems based largely on superstition and passed on by word of mouth.  These tribes today are not 'savages' and have moral rules enforced by the tribe.  For the previous 2 million years of hominid history we can only speculate (although a look at gorilla and chimpanzee groups might help) but its pretty safe to say our belief systems would have been very different from those today, probably atheistic in nature (e.g. animism rather than theism), and yet the shape of our moral behaviour was conducive to allow us to survive in social groups.  Clearly the rule that murder is generally bad, for example, would have applied in those primitive moral systems too.