Evolution And History

236 CHAPTER 10 | The Neolithic Revolution: The Domestication of Plants and Animals

Their bones are far more common in human refuse piles

than those of other animals. This is significant, for most

of these animals naturally move back and forth from low

winter pastures to high summer pastures. People fol-

lowed these animals in their seasonal migrations, mak-

ing use along the way of other wild foods in the zones

through which they passed: palm dates in the lowlands;

acorns, almonds, and pistachios higher up; apples and

pears higher still; wild grains maturing at different times

in different zones; woodland animals in the forested zone

between summer and winter grazing lands. All in all, it

was a rich, varied fare.

The archaeological record indicates that, at first, ani-

mals of all ages and sexes were hunted by the people of the

Southwest Asian highlands. But, beginning about 11,000

years ago, the percentage of immature sheep eaten in-

creased to about 50 percent of the total. At the same time,

the percentage of females among animals eaten decreased.

(Feasting on male lambs increases yields by sparing the fe-

males for breeding.)

This marks the beginning of human management of

sheep. As this management of flocks became more effi-

cient, sheep were increasingly shielded from the effects of

natural selection, allowing variants preferred by humans

to have increased reproductive success. Variants attractive

to humans did not arise out of need but at random, as mu-

tations do. But then humans selectively bred the varieties

they favored. In such a way, those features characteristic of

domestic sheep—such as greater fat and meat production,

excess wool, and so on—began to develop.

By 9,000 years ago, the shape and size of the bones

of domestic sheep had become distinguishable from

those of wild sheep (Figure 10.3). At about the same

flourish where people were living. Under such circum-
stances, it was inevitable that eventually people would
begin to actively promote their growth, even by deliber-
ately sowing them. Ultimately, people realized that they
could play a more active role in the process by trying
to breed the strains they preferred. With this, domesti-
cation shifted from an unintentional to an intentional
process.
The development of animal domestication in South-
west Asia seems to have proceeded along somewhat
similar lines in the hilly country of southeastern Turkey,
northern Iraq, and the Zagros Mountains of Iran. Large
herds of wild sheep and goats, as well as much environ-
mental diversity, characterized these regions. From the
flood plains of the valley of the Tigris and Euphrates Riv-
ers, for example, travel to the north or east takes one into
high country through three other zones: first steppe, then
oak and pistachio woodlands, and finally high plateau
country with grass, scrub, or desert vegetation. Valleys
that run at right angles to the mountain ranges afford rel-
atively easy access across these zones. Today, a number of
peoples in the region still graze their herds of sheep and
goats on the low steppe in the winter and move to high
pastures on the plateaus in the summer.
Moving back in time prior to the domestication of
plants and animals, we find the region inhabited by peo-
ples whose subsistence pattern, like that of the Natufians,
was one of food foraging. Different plants were found
in different ecological zones, and because of the differ-
ence in altitude, plant foods matured at different times
in different zones. Many animal species were hunted for
meat and hides by these people, most notably the hoofed
animals: deer, gazelles, wild goats, and wild sheep.

Wild hairy sheep Early woolly domestic sheep

Early domestic

hairy sheep

Hair follicle

Wool follicle

Hair follicle

Wool follicle

Rolling Uplands Anatolian Plateau

Mesopotamia

Both hairy and woolly

sheep being raised

AB

12,000 11,000 10,000 9,000 8,000 7,000 6,000 5,000

Years ago

Figure 10.3 Domestication of
sheep resulted in evolutionary
changes that created more wool.
Inset A shows a section, as
seen through a microscope, of
skin of wild sheep, showing the
arrangement of primary (hair) and
secondary (wool) follicles. Inset
B shows a section of similarly
enlarged skin of domestic sheep,
showing the changed relationship
and the change in size of
follicles that accompanied the
development of wool.