It is time to set aside the old term 'heliacal rising' insofar as the first annual appearance of Sirius is a lateral motion of a distant star with the central Sun as a focus for the Earth's orbital motion which makes the appearance possible -

http://www.skyandtelescope.com/obser...liacal-rising/

I suspect that a lifetime spent referencing stellar motion within the boundaries of the local horizon make it difficult for observers to adjust to a Sun centered perspective or leave behind a rotating stellar circumpolar framework limited to Polaris.

This feature could have presented at any time where the lateral appearance of Sirius displaces its 'rising' as the observer shifts emphasis to the orbital motion of the Earth alone.