Transcript The Origin of Agriculture

The Origin of Agriculture
“Cultural man has been on earth for some 2,000,000 years;
for over 99% of this period he has lived as a hunter-gatherer.
Only in the last 10,000 years has man begun to domesticate
plants and animals … Homo sapiens assumed an essentially
modern form at least 50,000 years before he managed to do
anything about improving his means of production … To
date, the hunting way of life has been the most successful and
persistent man has ever achieved” (Lee and Devore 1968:3)
Begin with the origins of Homo sapiens.
Most anthropology texts begin the line from apes to modern
humans about 5 MYBP with Homo habilis, or a more
generalized form, called Homo africanus. There are almost as
many schemes to get from the earliest Homo to us as there are
qualified anthropologists.
What they all have in common is an intermediate, Homo
erectus. They differ in having varying numbers of “side
branches” of Australopithecus spp.
The modern species, Homo sapiens, seems to have evolved by
about 500,000 years ago. It co-existed with H.
neanderthalensis from about 300,000 to 30,000 YBP
Australopithecus
reconstruction
Homo erectus
A comparison of the skulls of Homo neandrithalis and
Cro-magnon man (Homo sapiens)
A comparison of neanderthal
skeletal anatomy with that of
modern Homo sapiens.
The modern subspecies Homo sapiens sapiens was on the
scene about 170 KYBP.
They were hunter-gatherers. The ‘floors’ of campsites at
Olduvai Gorge show that humans ate a varied diet including:
fish, small rodents, fruits, roots and vegetables.
The evidence that shows what this diet includes: charred or
preserved remains of those foods, plant fibers, coprolites
(fossilized poop), seeds and pollen of consumed plants, and
microscopic evidence of crystals characteristic of particular
plants (phytoliths). From your text:
Plant remains clearly related to 25 different wild plant species
at Wadi Kubbaniya in the Nile River Valley have been dated to
~17,000-18,000 YBP.
Among those species are:
wild nut grass (a sedge) tubers – high in carbohydrates
and fiber, low in protein, but the protein is high in an
essential amino acid, lysine
acacia seeds – likely high in protein and lipids, as well
as carbohydrates
cattail rhizomes – rich in carbohydrates and fiber
palm fruits - carbohydrates
The tools needed to process those hunted and gathered foods
include grinding stones, digging tools (to gather tubers),
sickles to cut plants. The wear on hominid teeth indicates that
a fair amount of grinding occurred on eating.
There are still a few basically hunter-gatherer societies:
• !Kung San – savannahs surrounding the Kalihari desert,
southern Africa (Angola, Namibia, Botswana, Lesotho)
• Inuit – arctic Canada, Greenland, northern Russia, Alaska
– essentially
• Ainu – forced to move northward onto Hokkaido, the north
island of Japan by proto-Japanese cultures
• Australian Aborigines
• Bihors – northern India
Modern culture has impinged on all of these groups, probably
least so on the !Kung San.
Study of the !Kung San diet during the 1960s found they
utilized >100 plant species (about 2/3 of their diet) and 50
animal species.
The diet includes: mongongo nut, other fruits, berries, melons,
and roots; lizards, snakes, tortoises’ and birds’ eggs, insects
and caterpillars, and some small mammals trapped by the
women of the ‘tribe’. Meat from larger animals is only
infrequently available, and celebrated when returned to
villages.
Men are only allowed to marry after they have made their first
large animal kill.
!Kung San hunters
!Kung San musical instrument
Shepherd tree (Boscia albitrunca)
fruits and berries consumed, roots
used to make a coffee substitute
A gemsbok
Tsamma melon (Citrulus
lanatus) – watermelon-like,
except that it remains firm and
fresh for as long as 2 years.
A springbok
Caloric intake: 2,355 kilocalories/person/day
96 grams protein
Full daily requirement of vitamins and minerals
All this foraging only took 2.5 days/wk
Probably a healthier, and certainly a more efficient diet than
ours.
Inuit family in an igloo
Traditional hunting by kayak
A modern Inuit community, Kimmirut
(Lake Harbour)
Ringed seal (Phoca hispida)
being butchered on a beach
Blubber stew
Beluga whale being butchered
A few plants are consumed, e.g. fireweed, various berries,
Labrador tea, mountain sorrel. Most are high in vitamin
content.
Agriculture, meaning the culturing of plants and/or
animals, began between 10,000 and 14,000 years ago, and
arose without contact between cultures, at very similar times
in many places around the world.
What was first cultured differed among the key early sites?
Here is a global map of those early sites of agriculture:
Was the “origin” a revolution, or an evolution that involved
beginning to culture well-known wild plants? Almost
certainly the latter.
What was cultured represented a selection of plants key to
diets in the far-flung places where hunter-gatherer societies
shifted from nomadic movement to localized settlement.
In the fertile crescent (Iran, Iraq, Turkey, Syria, Lebanon,
Israel) remains indicating the beginnings of agriculture
date from 9,000 – 14,000 years ago.
1. Animals (dogs, goats, and sheep) were probably
domesticated well before plants
2. Barley was probably the first plant domesticated there
3. Followed by einkorn wheat, emmer wheat, pea, lentil and
vetch
Einkorn wheat and its distribution in the wild
Emmer wheat
There were a number of sites where plants were domesticated
in early agriculture in the Far East. The earliest site is along
the Yangtze R. in China. Agriculture spread both north and
south along the river.
1. Rice was domesticated ~11,500 years ago along the
Yangtze.
2. Later (~8000 years ago) along the Yellow R. foxtail millet
and, to lesser extents, broomtail millet, rapeseed
(predecessor of canola) and hemp
3. Slightly later (but completely independently) plants were
domesticated ~7,000 years ago in New Guinea highlands.
Main crop species were taro and banana.
4. Animals domesticated in the Far East included chickens,
pigs, dogs and cattle.
In the New World, in Mexican highlands and Peru, a large
number of plants and a few animals were domesticated,
beginning about 8 – 10,000 YBP.
1. The earliest dated domestication is squash from a cave in
southern Mexico. There are also phytoliths that indicate
squash had been domesticated in Ecuador between 9 –
10,000 years ago.
2. By around 5,500 years ago there are numerous evidences
of agriculture. Domesticated plants include: corn, chili
peppers, amaranth, avocado, gourds, beans, various white
(and coloured) potatoes, and sweet potatoes. Later peanuts,
guava, and tomatoes were added.
3. Domesticated animals were dogs, llamas, alpacas, guinea
pigs, and later muscovy ducks and turkeys.
Amaranth (Amaranthus
retroflexus) seeds are
ground into flour. It was
the main grain crop into
the time of early
European settlement.
Purple Peruvian potato, a
progenitor of the modern types
of potatoes.
In eastern North America (U.S. and Canada) agriculture began
independently about 4,000 years ago. The major crop species
were sunflower, marsh elder, wild gourd, and Chenopodium
album, common name lamb’s quarters.
Lamb’s quarters leaves are cooked as a pot herb, and taste a lot
like spinach, with similar food value.
Marsh elder (Iva spp.)
Admission of failure: I’ve been unable to learn how marsh
elder was used.
Corn – there is a long history. The original domesticated corn
was a perennial grass with very small cobs.
The originally domesticated wild corn was not the modern
agricultural species, Zea mays, but a perennial species still
found in some sites in the highlands of central Mexico, Zea
mexicana, common name teosinte.
grains
the plant
Through artificial selection and saving grains from better and
better Zea plants (probably mutants that appeared), we got
from teosinte to modern corn:
What are the characteristics that we might want in our
domesticated plants? How do those characteristics relate to
what can be expected from natural selection?
1. One of the first characters artificially selected (and
opposite from desirable characters from natural selection)
is how readily seeds are released and scattered from a
plant.
Natural selection points towards shattering fruit heads. Seeds
or fruits are readily broken free by weak force (a breeze,
and animal brushing by).
To harvest seeds we want agricultural plants to be nonshattering.
A single recessive gene makes Arabidopsis non-shattering.
The gene in this species (AGL 15) is called shatterproof,
and regulates the expression of other genes.
A plant scientist at UCSD (Marty Yanofsky) has applied this
genetic knowledge to canola growth.
On the left, an Arabidopsis thaliana plant, and on the right the
seed head of a shatterproof arabidopsis.
2. Plants are naturally selected to maximize fitness. In many
cases that results in the production of smaller fruits, tubers
or seeds, but larger numbers. In small-seeded plants like
cereal grains the reverse may occur, with larger seeds
having greater survivorship. We generally want more and
larger.
In barley, two-rowed barley
is the wild character, while
domesticated barley is sixrowed. The presence of sixrowed barley is considered
an indication of agricultural
domestication.
The story of strawberries shows the results of sheer luck in
artificial selection. Wild strawberries are tiny – the size of
your little fingernail. There are a number of genetically
distinct wild strawberries.
There are two in Europe – a smaller English one and a
somewhat larger one from Alpine meadows.
In North America there is a wild scarlet strawberry and in
South America a large-fruited, pale yellow strawberry
described as tasting like pineapple.
The two New World strawberries were exported back to
France and, grown in common gardens, crossed by chance.
Result: large size, almost scarlet colour, and lots of flavor.
3. We select for cooking and/or mechanical properties that
clearly have nothing to do with natural selection. Two
examples:
•
Nearly all commercial french fries are cut from ‘Russet
Burbank’ cultivar
•
Selection for fruit shape optimizing shipping qualities is
ongoing in tomatoes and watermelon
4. Winter dormancy is naturally selected. The mechanism is
frequently hormonal. Abscisic acid accumulates in the seed
coat of maturing seeds. It prevents embryo germination
even when hydrated. It is broken down by an extended
period of cool, wet conditions (spring).
Selection for early or rapid germination (probably) selects
for lower levels of sequestered abscisic acid in seed coats.
This has been achieved in rapeseed. Its seed oil is used in
cooking and for ‘biodiesel’ fuel.
Sometimes the artificial selection introduces problems that
were not, but (probably) should have been expected:
1. Selection for reduction in anti-herbivore chemicals, e.g.
mustard oils, in a number of agricultural Brassicacea
(canola,…) make them more vulnerable to pest insect
attack.
2. Large scale monocultures produce large sources of cueing
chemicals that attract insect herbivores, e.g. glucosinolates
in crucifers (cabbage) attract diamondback moths. In us the
glucosinolates (toxins) can cause liver and kidney lesions
and thyroid enlargement.
3. Chemical content we want (higher sugar content in
strawberries (Fragaria vesca) attracts egg-laying insect
pests like aphids.
We know where some of our agricultural plants were first
domesticated, but where do modern agricultural species come
from originally?
A Russian geneticist, Nikolai Vavilov, gathered much of the
early, key evidence from 1916-1936. His research was ended
when he was sent to the Gulags. He was a Mendelian
geneticist, but the Stalinist leader of agricultural genetics was
Trofim Lysenko, who believed (mistakenly) in Lamarkian
genetics. Vavilov died in the gulags in 1943.
Vavilov proposed eight centers of origin, shown on the map of
figure 11.6.