No not really. In early cultures religion was often devoted to more everyday things and fears, like illness, lions, and hunger. Fear of death perhaps always existed to a degree, but a lot of exaggerated fear of death was created by religion. Since as they are always using the god of the gaps, anywhere they can find mystery they can create fear and pretend to have answers. So since they are selling fake gap filler, it pays to exaggerate the size and importance of the gaps. A huge amount of religious propaganda has being devoted over the years to promoting a fear of death, and building that exaggerated fear into our cultures.

Humans did not create the ideas of religion and life after death out of fear of death, they created it for the use of those in power to retain power.
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"Therefore it is unnecessary for a prince to have all the good qualities I have enumerated, but it is very necessary to appear to have them. And I shall dare to say this also, that to have them and always to observe them is injurious, and that to appear to have them is useful; to appear merciful, faithful, humane, religious, upright, and to be so, but with a mind so framed that should you require not to be so, you may be able and know how to change to the opposite." - Niccolo Machiavelli