Origin hypotheses[ edit ] Indigenous Australian camp by Skinner Prout, Scholars have developed a number of hypotheses to explain the historical origins of agriculture.
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Studies of the transition from hunter-gatherer to agricultural societies indicate an antecedent period of intensification and increasing sedentism ; examples are the Natufian culture in the Levantand the Early Chinese Neolithic in China.
Current models indicate that wild stands that had been harvested previously started to be planted, but were not immediately domesticated. An abundance of readily storable wild grains and pulses enabled hunter-gatherers in some areas to form the first settled villages at this time. List of food origins Sumerian harvester's sickle, 3, BC, made from baked clay Early people began altering communities of flora and fauna for their own benefit through means such as fire-stick farming and forest gardening very early.
An example is the semi-tough rachis and larger seeds of cereals from just after the Younger Dryas about 9, BC in the early Holocene in the Levant region of the Fertile Crescent.
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Monophyletic characteristics were attained without any human intervention, implying that apparent domestication of the cereal rachis could have occurred quite naturally. Similar ploughs were used throughout antiquity.
Agriculture began independently in different parts of the globe, and included a diverse range of taxa. At least 11 separate regions of the Old and New World were involved as independent centers of origin.
Domestic pigs had multiple centres of origin in Eurasia, including Europe, East Asia and Southwest Asia,  where wild boar were first domesticated about 10, years ago.
Area 3 grey is no longer recognised as a centre of origin, and Papua New Guinea red, 'P' was identified more recently.
Feed source[ edit ] As in most aquaculture based systems, stock feed often consists of fish meal derived from lower-value species. Ongoing depletion of wild fish stocks makes this practice unsustainable.
Organic fish feeds may prove to be a viable alternative that relieves this concern. Other alternatives include growing duckweed with an aquaponics system that feeds the same fish grown on the system,  excess worms grown from vermiculture composting, using prepared kitchen scraps,  as well as growing black soldier fly larvae to feed to the fish using composting grub growers. The system relies on the relationship between the animals and the plants to maintain a stable aquatic environment that experience a minimum of fluctuation in ambient nutrient and oxygen levels.
Plants are able to recover dissolved nutrients from the circulating water, meaning that less water is discharged and the water exchange rate can be minimized. Aquaponic systems can also be used to replicate controlled wetland conditions. Constructed wetlands can be useful for biofiltration and treatment of typical household sewage. However, if a system is designed with energy conservation in mind, using alternative energy and a reduced number of pumps by letting the water flow downwards as much as possible, it can be highly energy efficient.
While careful design can minimize the risk, aquaponics systems can have multiple 'single points of failure' where problems such as an electrical failure or a pipe blockage can lead to a complete loss of fish stock.
Fish stocking[ edit ] In order for aquaponic systems to be financially successful and make a profit whilst also covering its operating expenses, the hydroponic plant components and fish rearing components need to almost constantly be at maximum production capacity.
Multiple age groups of fish share a rearing tank, and when an age group reaches market size they are selectively harvested and replaced with the same amount of fingerlings. Large quantities of fingerlings are stocked at once and then split into two groups once the tank hits maximum capacity, which is easier to record and eliminates fish being "forgotten".