The primary addressee of this message is Sabine, who asked
about Sherratt's secondary products revolution. But I'd like to invite
comments from anyone iterested in linguistic palaeontology.
The term "secondary products revolution" was introduced by A.
G. Sherratt (1981, 1983); it refers to the "second Neolithic
revolution" dated at the late fourth millennium BC and characterised by such innovations as the exploitation of domestic
animals for traction (especially for pulling ards and wheeled vehicles), the
processing of the secondary products of animal husbandry (milk, wool, hides) to
make further derived products (such as cheese or woven textiles), and the use of
animal fertiliser. As a result, previously neglected areas became suitable for
colonisation, and road systems were built to enable the bulk transport of raw
materials and finished products across long distances.
As PIE seems to have had words for concepts associated with
the secondary products revolution (ard, yoke, wagon, wheel, axle, wool, weave,
etc.), linguistic palaeontology suggests that the dispersal of IE languages must
have taken place somewhat later (say, 3000-2500 BC) -- of course if the premises
are correct, i.e. if there was a second Neolithic revolution at all, if the
cultural inventions in question have been correctly dated, etc.
Piotr