Plant and Animal Domestication - Lifelong Learning Mississauga

Plant and Animal Domestication - Lifelong Learning Mississauga

People and Planet Earth 4 Plant and Animal Domestication From last week; 1. subantarctic lakes

2. asteroid impacts and plate tectonics 3. evolution of whales

Subantarctic lakes There are nearly 400 known subglacial lakes in Antarctica. The largest is Lake Vostok. Its 500 m below sea level, 250 km long and 50km wide. Lake temp. is about -3C.

Water is replenished every 13,000 years. Presence of water related to pressure of ice and geothermal heat. In another lake, Lake Whillans, there are over 4000 species of microbes. No photosynthesis so

they survive by processing methane, sulphur and iron. Asteroid impact and plate tectonics Most of the literature focusses on the

early Earth and the premise that at around 3.6 billion years ago a large asteroid (1000 km diameter) fractured the crusted Earth to initiate PT. The kink in the Hawaiian seamount chain has also been interpreted as a product of impact.

Evolution of whales Whale evolution probably began around 50 MY ago from the same

animal group that contains the hippopotamus. The earliest ancestor appear to be Eocene. Whales derive from the Pakicetidae, the first cetaceans.

Human impact on environment seems to have been modest until the Late Pleistocene/Early Holocene. By then humans had developed increasingly sophisticated material technologies and complex social arrangements.

We saw earlier that our first major impact may have been our role in the extinction of the Late Pleistocene megafauna. The transition from the LP to the Holocene is marked in a large

number of places by a major change in human-biosphere interactions the domestication of plants and animals.

In 1987, Jared Diamond described plant and animal domestication as The Worst Mistake of the Human Race (Discover Magazine). He claimed that the process brought with it malnutrition, starvation, epidemic disease and class and gender divisions.

This suggests that conscious decisions were to adopt domestication over foraging. As we shall see, it wasnt that simple. Before we get into this, we need a few basic definitions;

Cultivation the use and management of plant resources which may or may not involve domestication. Domestication the use and management of plant and animal resources in such a way as to make them dependent on human intervention for

establishment and survival. Agriculture most assume that this is related to the scale of activity and the complexity of the manipulation.

These changes began with a stone technology, in the Neolithic. The process of domestication has been called the Neolithic Revolution, but in most places the changes were the consequence of long and increasing interactions between

people, plants and animals; perhaps an inevitable extension of huntergatherer economies. Interactions between people and their food plants Domestication has been described as an evolutionary continuum of plant-people interaction.

Simply, humans applied selective pressures. Initially, these would have been accidental; a consequence of food gathering, for example. Emmer wheat Accidental selection for non-shattering

wheat What was domesticated? Where and when did it happen?

How and why did it happen?

What was domesticated? Plants and animals existing in close proximity to humans components in the foraging economy, weedy species around camp sites, etc. For plants, these were species that were

(a) pre-adapted to domestication, (b) mostly disturbance related, (c) genetically flexible (polyploidy), and (d) were commonly self-fertilizing. The earliest plant domesticates were cereals. Plants less easily manipulated were domesticated later. These include crops grown as vegecultures and tree crops.

Species of wheat (Triticum) from the Middle East Rice The worlds major food crops

For animals, suitable animals were those that; Were dietary generalists Had a strong herding instinct Were unaggressive Were non-territorial Were promiscuous maters Were easy breeders

Had a fast growth rate Were multipurpose animals Where and when?

First, its useful to consider how where is determined. What lines of evidence suggest domestication? (a) settlement form and function (b) animals remains (type, age, size of bones,etc). Zooarcheology. (c) archeobotanical remains (carbonized plants remains, pollen, etc.) (d) impressions and residues on pottery and

tools (e) food procuring and processing tools (f) isotopic composition of human bone, dentition, coprolites, etc.

Crop marks Bronze age hut circles and enclosures

Magnetometer survey Ground penetrating radar Skara Brae, Orkney, a Neolithic village about 5000 years old House interior, Skara Brae

Bronze Age urn burial Carbonized materials recovered by flotation Pollen grains Corn pollen Farming tools sickles and scrapers

More tools sickles, manos and metates (mortars and pestles) Where? Plants and animals seems to have

been domesticated in several widely spaced locations in a variety of environments. This suggests independent origins. A number of hearths of domestication are recognized. Some are small but others are less defined (centres and noncentres).

Early centres of food production What was domesticated and where Centres of animal domestication Fertile Crescent

Nowhere else had the same richness of plants and animals available for domestication When?

Depends on what is taken as a reliable indicator of domestication, and the ability to date items considered to represent the process (14C and AMS). Until recently is has been assumed that the earliest domestication was that of wheat and barley in the Fertile Crescent, perhaps 10,500 BP. New AMS dates on

rice from China may change that view. How and why?

These are the most difficult questions to resolve. Domestication can be seen as a consequence of mostly accidental selection pressures that make plants and animals increasingly dependent on human intervention. People become critical for protection and reproduction. How does

this work?

For plants, increasing interaction meant; (a) general increase in size (for plants) and in the size of the part used by people (seed, root, etc.) (b) genetic changes (polyploidy)

(c) reduction in ability to disseminate naturally (d) loss of delayed seed germination (e) simultaneous crop ripening

(f) loss of protective mechanisms (g) increased diversity in form and function (local races) . The most common rice species is Oryza sativa, but there are probably over 80,000 races. (h) changes in life style (annual to perennial)

Corn and its progenitor Teocinte For animals, increasing interaction meant; (a) increasing dependence on humans for food, protection, etc. (b) increasing selection for certain attributes (meat, wool, hides, etc.) (c) changes in life cycles, etc.

Why? The most difficult question to answer. Why would people who had existed as foragers for so long and apparently

successfully change their basic system of food procurement? A number of hypotheses have been proposed. A. Environmental Change;

The Pleistocene-Holocene boundary was a time of rapid environmental change. Perhaps traditional foods were no longer available and alternatives needed to be found. Some have suggested that the Younger Dryas, an early Holocene episode of rapid climate shift

may have been responsible. This coincidence only works well for the Middle East and China.

In many other places the process is obvious only well into the Holocene. B. Population Pressure;

Simply put, increasing population forced foragers to adopt agriculture. On what grounds? More food per unit area? How would they know? In general, population pressure is considered a consequence not a cause.

C. Coevolution; Here domestication is seen as a natural consequence of long-term interaction between people, plants and animals. Many of the things domesticated were pre-adapted.

Part of the answer, but it doesnt explain when. D. Optimal Foraging; This hypothesis suggests that

changing food supply associated with overexploitation may have forced people to adopt alternative food sources and different production strategies. All of these hypotheses have merit, but no single one is sufficient.

Consequences

In essence, plant and animal domestication allowed the emergence of civilization. Food surplus brought population increase, sedentism and urbanization. Stratification of society. Centralized government.

Organized religion. Art, writing, warfare, colonization, etc. Environmental degradation. Next week well take a look at some of those early societies ; at how and where they were

established and why they declined.

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