If I told you that a bunch of Namibian people had kept the same
cultural mythology alive for over 70000 years, you'd probably think I
was a total nutjob or at least completely hopeless.
Well, you'd be right. The culture hasn't stayed the same.
However, the same creation myth has survived relatively unchanged for
just that long.
http://www.livescience.com/history/061130_oldest_ritual.html
Now, of course, this is many thousands and thousands of kilometres
(not to mention of years!) from our dear old Proto-Indo-Europeans.
HOWEVER! This dumbfounding survival of mythological tradition has
great gravity for us, as it does for any anthropology-based field of
study. This proves what has long been suspected: to paraphrase
Nietsche, mythology is deep, and deeper than we remember!
To prove that this example is not unique to the San culture, I invite
you to look at the most isolated continant and its cultures. There is
a common myth among most of the Australian Aboriginal cultures
of "The Dreaming", the childhood of the world. Now, judging from the
linguistic divergence of these cultures, they could not have
descended from a single tongue any later than - don't quote me, but
something to this effect - 40000 years ago. Yet they managed to keep
this common creation mythology!
How can this relate to PIE? Simply, this means that what we construct
mythologically could well be older than we think. Now, I know that we
have no undisputedly PIE artifacts, but the very fact that such
survival of tradition exists of ver such periods of time speaks for a
greater importance that ought to be placed in this field of research.
Also, one might do well to find similar elements in mythology and
tradition in other cultures, while obviously keeping in mind language
similarities and commonalities due to borrowing or environment.