Proto Indo Europeans used agricultre.
http://en.wikipedia.org/wiki/Proto-Indo-European_society
"Proto-Indo-European society depended on animal husbandry. Cattle
(*gʷōus) were the most important animals to them, and a man's wealth
would be measured by the number of cows he owned. Sheep (*H₃ówis) and
goats (*gʰáidos) were also kept, presumably by the less wealthy.
Agriculture and catching fish (*písḱos) were also practiced."
http://www.geocities.com/Paris/LeftBank/6507/chronicle120.html#technol
ogy
"We can learn more about the earliest Indo-Europeans from other
aspects of their reconstructed vocabulary. Some words, for example,
describe an agricultural technology whose existence dates back to
5000 B.C. By that time the agricultural revolution had spread north
from its origins in the Fertile Crescent, where the first
archaeological evidence of cultivation dates back to at least 8000
B.C. From this region agriculture also spread southward to sustain
the Mesopotamian civilizations and westward to Egypt. The Indo-
European words for "barley," "wheat" and "flax";
for "apples," "cherries" and their trees, for "mulberries" and their
bushes; for "grapes" and their vines; and for the various implements
with which to cultivate and harvest them describe a way of life
unknown in northern Europe until the third or second millennium B.C.,
when the first archaeological evidence appears."
http://www.robotwisdom.com/science/pie/
"They had already adopted livestock-herding from the non-caucasian
mideast where agriculture had been evolving for 5000 years, and where
small cities were already starting to form, though writing was still
a millennium off.
Reconstructed pIE vocabulary likely included: cow, ox, steer, cattle-
raid, sacrifice, butter, cheese, plow, yoke, wheel, axle, boat,
sheep, wool, weaving, belt, pig, horse, dog, grain, sowing, grinding,
sickle, house, post, door, doorpost, hearth, clan, chief, fort, pot,
whetstone, hemp, flax, bow, arrow, dagger, fart, widow, lead-home
(wed), put-heart (worship), father-god, sun-god, storm-god, three
estates (white priest, red warrior, dark farmer), three cures
(spells, surgery, herbs), twin, right-good, left-sinister"
another theory
http://www.esd.ornl.gov/projects/qen/Indo2.html
Kelkar: So the extent to which reconstrcuted PIE vocabular reflects
agriculture can be used both to support and refute Renfrew's theory.
M. Kelkar