lecture 9: Documenting domestication Flashcards
LAST LECTURE - TAKEAWAYS
mtDNA (non-recombinant) and
nDNA (recombinant through sexual
reproduction) are two types of
genetic information that can reveal
the precise timing and nature of
domestication
7 lessons for the power, use and
limitations of genetic techniques.
SUMMARY OF GENETIC
APPROACHES
DNA can address many questions in
domestication
Only as good as the biological and
genome samples available
Wild populations have changed a lot since early Holocene: need ancient DNA!
DNA cannot always distinguish between independent domestications and gene flow from new wild populations
Recent breeding programs have
significantly modified domestic populations
CAUSAL CHAIN OF DOMESTICATION
behavioural change > genetic change >morphology change
Behavioural markers
1. Circumstantial evidence of
the relationship between
humans, animals and
plants.
Morphological Markers
1. Genetically driven, heritable,
selective responses to domestication (is passed down)
2. Plastic responses in individual
animals that are more episodic
in nature.(is occuring during the life of an individual animal)
BEHAVIOURAL MARKERS:
PLANTS
- Archaeological/Artifact
evidence (technologies) -
Ecological Evidence
ex:large field - Biomolecular evidence (isotopes, residues)
- Historical Sources, Iconography
NEW ARTIFACTS &
TECHNOLOGIES
New tools and technologies
Field preparation (hoes)
Plant collection and processing
(scythes, grinding stones)
Food storage (ceramics)
New archaeological features
Storage pits or silos
Field walls, hearth
Threshing floors
PLANT MACROFOSSILS &
MICROFOSSILS
Macrofossils
-Charred/desiccated seeds, nuts, pits,
-Charred/desiccated husks, stems, cobs
Microfossils
-Pollens, Starches, Phytoliths
Reflect use of different parts of the plant
May be species specific
NEW FOODS IN THE DIET
Microscopic analysis of dental
calculus to reveal new plant
foods
- Plant starches & phytoliths
Especially important for
vegetatively propagated crops
which decay in archaeological
contexts
Banana seed phytoliths found in
the tartar of Lapita people in
Remote Oceania shows the
import of early banana cultivars
ECOLOGY & LANDSCAPE
Evidence for anthropogenic landscape
alterations
Field systems
Pollen evidence for forest clearing &
burning
Weedy species that thrive in disturbed soils
Water management
-Canals, check dams
-May occur millennia after adoption of
crops
AMAZONIAN
DARK EARTHS
Plant remains rarely preserve
in tropical environments
Small patches of highly fertile
soils - Anthropogenic Dark
Earths (or terra preta de Índio).
High nutrient and soil organic
matter stocks and allow sustainable agriculture.
Pot-sherds of pre-Columbian
origin and settlement activities
show terra preta is human
made.
STABLE ISOTOPE ANALYSIS
- Isotopic analysis of human bones can reveal food pathways, individual long-term food intake.
-
Isotopes are atoms of the same element but with different masses
(same # of protons but with a different # of neutrons) -
Stable isotopes do not decay through time (14C is not stable
isotope)
Carbon (C)
mass of 12 = 12C
mass of 13 = 13C
know the graph!
CARBON ISOTOPES
- During photosynthesis, plants discriminate against heavier 13C, and instead preferentially take up 12C (i.e., containing a smaller proportion of 13C than atmospheric CO2) (~ -6.5 to -35‰)
Temperate plants (C3),:
* take up very little 13C (depleted)
* Majority of plants (95%):
rice, wheat, barley, potatoes, etc.
Drought adapted plants
(C4)
* take up relatively more13C (enriched)
* Some tropical cereals: Maize, sorghum, sugarcane, millet…
VARIATION BY FOOD SOURCE AND
SPECIES
- lower in the food hierchy have lower isotope
ex:plants.deers - because the higher ups are eating the lower isotops witch add to their own
ISOTOPES ANALYSIS OF DIET
Carbon (C13) δ13C (C13/C12)
Diet with C4 plants
(maize in Americas; millet in SE Asia);
Diet is derived from marine or
terrestrial protein source
Nitrogen (N15) δ15N (N15/N14)
Indicates “trophic level” (how high on
the food chain, how much protein was
obtained)
δ (lower case Δ delta) - denotes
relative differences of ratios between stable isotopes
INTRODUCTION OF MAIZE
- Enriched C13 values of human bone collagen after 500AD provided
the first evidence for maize cultivation in North America
INTRODUCTION OF FARMING
Depleted C13 values of human
bone collagen after 5,000BP provided
evidence from the shift from marine
resources (hunter- gatherers) to
terrestrial sources (farmers) in Britain
AGRICULTURAL INTENSIFICATION
The use of fertilizers
increases N15
ICONOGRAPHY & HISTORICAL
SOURCES
Imagery or documenting relating to interactions between humans and plants.
Propagating techniques
Physical appearance
Economic transactions
Document later aspects of domestication
