BLGY1211 Domestication and Agriculture 2
Initial domestication
Hunter-gatherer societies knew nothing about genetics, breeding inheritance ect but
they probably knew a huge amount about local plants and animals
They had no teleological goal of domesticating crops but may have had the goal of
increasing food supply
Pre-conditions for domestication
In the case of plants – sedentary lifestyle; somewhere to grow plants
Knowledge and management of local species
Pre-farming societies in the Levant – diet included at least 157 species of plant
Hunting and herding of animals a likely precursor for their domestication
Unconscious domestication
The best candidates or domestication were practically there already
Edible, high-yielding, storable (and fast-growing, self-pollinating)
H-g societies in the fertile crescent already harvested wild grasses
Yield of 1 ton/hectare; 1 kcal spent harvesting 50 kcal of seed
Provided a stable source of food throughout the year
Wild barley and wheat spikes shatter – seed dispersal
Harvesting and transporting automatically selects for shatter resistant spikes and
tends to select for largest grains
Storing inevitably leads to escapees
Shatter-resistant grasses growing nect to settlements; a massive bonus
You can purify natural variation without thinking about it
The key human decision is to actively re-plant from locally harvested seeds
Wild grass seeds are programmed to germinate over ~4 year periods
By planting, harvesting and re-planting, plants with weak dormancy and synchronous
germination were automatically selected for These two changes were sufficient
for wheat/barley domestication
Many subsequent improvements, but not needed for the initial domestication
Maize was domesticated by the same general process
A much slower process, because the wild ancestor was far from an ideal crop
therefore greater degree of improvement required
The teosinte-maize kinship has only been recently recognised teosinte seeds likely
gathered as a last resort by h-g’s
5 major genetic changes occurred and all were unconsciously selected for;
Prevention of seed dehiscence
Reduction in seed case
Increase in ear size
Increase in flower number
Alteration of branching architecture
Maize took much longer to domesticate because;
It had lower potential to begin with
More major genetic changes were needed to domesticate it
Combining traits without knowledge of plant breeding is difficult
Initial domestication
Hunter-gatherer societies knew nothing about genetics, breeding inheritance ect but
they probably knew a huge amount about local plants and animals
They had no teleological goal of domesticating crops but may have had the goal of
increasing food supply
Pre-conditions for domestication
In the case of plants – sedentary lifestyle; somewhere to grow plants
Knowledge and management of local species
Pre-farming societies in the Levant – diet included at least 157 species of plant
Hunting and herding of animals a likely precursor for their domestication
Unconscious domestication
The best candidates or domestication were practically there already
Edible, high-yielding, storable (and fast-growing, self-pollinating)
H-g societies in the fertile crescent already harvested wild grasses
Yield of 1 ton/hectare; 1 kcal spent harvesting 50 kcal of seed
Provided a stable source of food throughout the year
Wild barley and wheat spikes shatter – seed dispersal
Harvesting and transporting automatically selects for shatter resistant spikes and
tends to select for largest grains
Storing inevitably leads to escapees
Shatter-resistant grasses growing nect to settlements; a massive bonus
You can purify natural variation without thinking about it
The key human decision is to actively re-plant from locally harvested seeds
Wild grass seeds are programmed to germinate over ~4 year periods
By planting, harvesting and re-planting, plants with weak dormancy and synchronous
germination were automatically selected for These two changes were sufficient
for wheat/barley domestication
Many subsequent improvements, but not needed for the initial domestication
Maize was domesticated by the same general process
A much slower process, because the wild ancestor was far from an ideal crop
therefore greater degree of improvement required
The teosinte-maize kinship has only been recently recognised teosinte seeds likely
gathered as a last resort by h-g’s
5 major genetic changes occurred and all were unconsciously selected for;
Prevention of seed dehiscence
Reduction in seed case
Increase in ear size
Increase in flower number
Alteration of branching architecture
Maize took much longer to domesticate because;
It had lower potential to begin with
More major genetic changes were needed to domesticate it
Combining traits without knowledge of plant breeding is difficult
