With modern techniques for recording and dating botanical remains from archaeological sites and genetic studies to determine the relationships between wild and domesticated plants, their research pulls together a huge mass of information produced by scholars in various disciplines and provides a strong theoretical framework in which to interpret it. Key features include: arguments that tropical forest food production emerged at approximately the same time as that in the Near East and is earlier than currently demonstrated in highland Mexico and Peru; and contends that the lowland tropics witnessed climatic and vegetational changes between 11, BP and 10, BP, no less profound than those experienced at higher latitudes.
It appeals to anyone concerned with Latin American prehistory. It offers coverage of the development of slash and burn or swidden cultivation and, focuses on low and lower mid-elevations. Boks - K. Wybierz pakiet! Oferta od Osoby prywatnej.
The Paleobiolinguistics of Domesticated Manioc (Manihot esculenta)
On the other hand, the process of domestication has influenced significant changes of human societies and cultures. Domestication is recognized to be a continuous process that may occur on wild managed plant populations as well as in fully domesticated plant stands which are completely dependent on humans to survive and reproduce [ 3 , 6 , 11 ].
In areas where wild relatives of crops and the domesticated organisms coexist it is possible to identify continuous gradients of states or degrees of dependence of plant fitness according to the types of human actions [ 3 , 6 ]. Those plants that can be propagated and managed by people, but not necessarily depend on them for completing their life cycle are called by some authors semi-domesticated or incipient domesticates [ 6 ]. Incipiently domesticated plants are those that are in early stages of domestication, with relatively low phenotypic and genetic differentiation compared with their wild relatives.
Clement [ 28 ] has claimed a distinction between species in incipient state of domestication and those that are semi-domesticated. According to this author, incipient domesticated plants exhibit phenotypic variation within the range normally found in wild populations, whereas semi-domesticated plants are characterized by greater phenotypic variations than their wild ancestors, including the emergence of new characteristics [ 28 ]. However, plant populations of plant species in the wild and at initial stages of domestication may show patterns of high morphological variation associated to natural selection and therefore, other additional indicators are needed to arrive to a conclusion about the initial, intermediate or advanced degrees of domestication of plant populations.
The fact is that variation in plant populations may diverge by both natural and cultural processes and in all studies of domestication it is necessary to understand which aspects are influenced by natural factors and which ones by human culture. Therefore, more precise typologies for systematizing the degrees of variation between wild and managed populations are still needed. In all concepts of domestication, artificial selection is considered as the main evolutionary force, which is in turn influenced by cultural and ecological factors, as well as the amount of gene flow among wild and domesticated relatives.
Studying integrally all these factors is necessary to understand how domestication occurs. Some authors identify plant populations that have incidentally co-evolved with crop plant species e. According to Clement [ 28 ], weeds are plant populations adapted to disturbed habitats, possibly experiencing changes in their genetic structure resulting from ecosystem changes determined by humans although, in most cases, without direct human selection and management.
Landraces populations of semi-domesticated or fully domesticated plants display high phenotypic and genetic variation in particular geographic areas. In other extreme, modern cultivars have reduced genetic variation because of the high selective pressure and modifications made to better adapt them to intensive monocultures [ 19 , 26 , 29 — 31 ].
The Origins of Agriculture in the Lowland Neotropics
The interactions between people and plants start in their wild environment. Interactions become more complex with protected, enhanced or cultivated plants, and even more with plants involving different levels of artificial selection and domestication degrees [ 17 , 22 ]. Studying plant species in incipient and advanced stages of domestication make possible to analyze it as an evolutionary continuum of intensity of management and artificial selection, especially in areas where managed and wild populations coexist.
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In these areas it is possible to verify gene flow between wild and domesticated populations, their influence in maintaining local diversity, and the influence of natural and artificial selection on their genetic structure. But this is also possible among populations of plant species under incipient stages of domestication, which offers the opportunity to analyze how human management of plants could be in the early stages of agriculture. The Mesoamerican region is one of the main settings of domestication of plants in the world [ 1 — 3 , 5 , 16 , 32 , 33 ], and important research projects have been and are still being developed in that area to understand cultural and biological principles involved in the process.
These researches provide insight into factors that originated agriculture and mechanisms of evolution under domestication [ 9 , 23 , 26 ]. According to [ 34 ], studies on management forms of plant populations and communities by traditional cultures allows analyzing processes of domestication since it has measurable results. It is possible to investigate cultural aspects of artificial selection, management methods involved and to quantify the effects of such practices on biological variables of plant populations. Studies in Mesoamerica have allowed the identification and characterization of three main types of plant population management strategies by traditional communities: gathering, incipient management, and cultivation of domesticated plants or agriculture.
It is also worth noting that this gradient can be observed in hundreds of species of dozens of plant families. Some in depth studies have been conducted with members of the families Agavaceae [ 20 ], Bombacaceae [ 35 ], Cactaceae [ 21 , 36 — 41 ], Malpighiaceae [ 42 ], Solanaceae [ 43 — 50 ], Curcubitaceae [ 51 , 52 ] and Fabaceae [ 53 — 62 ] among others, and some general management patterns and evolutionary trends of managed plants have been identified in the Mesoamerican region. Several authors analyzing forms of incipient management of plants have identified the following types of management: tolerance, protection, and promotion [ 17 , 22 , 64 ].
Individual plants with desirable traits to the humans that manage them can be tolerated in particular areas, promoted by dispersing their vegetative or sexual propagules, and protected from competitors or herbivores [ 27 , 35 , 64 ]. However, all these practices not only involve the intention of increasing numbers of desirable plant resources.
Also, people look for increasing the better resources and this practices involve artificial selection favoring quality of the resources managed in a system. According to these authors, selective incipient management is directed to increase and maintain the availability of desirable phenotypes in a population, with a consequent reduction in the frequency of undesirable phenotypes. Such a process may therefore maintain or increase the availability of desirable resources and increasing their quality according to human values.
These authors concluded that plants are within a gradient of management intensity following a gradient of manipulation from simple gathering of useful plant products to nonselective incipient management, selective incipient management, occasionally ex situ cultivated plants, and permanently cultivated domesticated plants. Blancas et al. The type and intensity of artificial selection associated to the different management forms discussed above trigger a series of structural changes which may be part of what has been called domestication syndromes [ 6 , 16 , 18 ].
Such syndromes are not easily discernible in species at incipient stage of domestication [ 52 ], but trends and consequences of selection are measurable and therefore analyzable from different perspectives as discussed below.
The characteristics of the domestication syndromes were proposed mainly based on studies of annual species from temperate areas [ 65 ]. However, hundreds of plant species domesticated throughout the world have different characteristics; therefore, a deeper analysis of domestication syndromes deserves a broader scope of human experiences and ecological contexts and evolutionary trends associated to these variable aspects. Artificial selection acting on plant populations may determine morphological, physiological, reproductive, and genetic changes, leading to phenotypic and genotypic divergence between wild and managed populations; the desirable characteristics being conserved and promoted by management practices [ 36 , 40 , 54 ].
Examples of this process have been extensively documented in Mesoamerican annual plant species such as maize Zea mays , common beans Phaseolus vulgaris [ 66 ] and Phaseolus lunatus [ 61 ]. Among perennial plant species, several members of the Cactaceae family especially columnar cacti and prickly pears, whose fruits are consumed by local people are among the most studied [ 17 ]. For instance, species of Opuntia [ 67 ] and columnar cacti such as Stenocereus stellatus Pfeiffer Riccob.
Weber F. Species such as Leucaena esculenta Moc. Agave species, such as A. In the case of Cactaceae, studies of wild, managed in situ, and cultivated populations showed that their edible fruits are highly appreciated by local people of several regions of Mexico. Fruit size smaller sizes usually being more frequent in the wild whereas larger sizes are more frequent in cultivated populations , taste sweeter fruit are more frequent in cultivated populations , thorniness plants of wild populations are thornier , and mesocarp color mainly red pulp in wild populations and other colors being more frequent in cultivated populations are the main characteristics under selection [ 21 , 36 — 38 ].
Phenotypes producing fruit with the most desirable attributes according to local people are cultivated, which represents the highest level of artificial selection intensity.
In the managed in situ or silviculturally managed populations the wild individuals showing the best attributes are let standing and enhanced and this artificial selection is relatively less intense than that practiced in cultivated populations. Leucaena esculenta Fabaceae is another tree species studied in the context of incipient domestication. The number of seeds higher amounts in those cultivated and managed in situ , the size of seeds and pods larger in those cultivated and managed in situ than in the wild are the variations that are most relevant to the morphological differentiation of wild populations, those tolerated in situ, and those that are cultivated.
Also, flavor of seeds was identified as a relevant characteristic for local people. The phenotypic patterns found in cultivated and tolerated populations included traits that were more desirable compared to traits in wild populations [ 17 , 54 , 73 ]. The reproductive biology of some species has been studied hypothesizing changes in breeding systems associated to human management.
Studies in several species of columnar cacti revealed that in most of them either wild and managed populations have self-incompatible breeding systems, indicating that in those cases artificial selection has not altered their breeding system [ 27 , 74 ].
However, in species such as Polaskia chichipe [ 41 ] and Myrtillocactus schenckii [ 39 ], self-compatibility occurs in wild populations and is significantly more frequent in silviculturally managed and cultivated populations. In addition, different animal species visit flowers of wild and managed populations, and periods of blooming peak may also differ among populations. Therefore, in addition to artificial selection, the reproduction systems may also help to explain morphological and genetic differentiation of wild and managed populations [ 27 , 39 , 41 , 75 ].
Human manipulation of natural resources not always decreases genetic diversity [ 76 ]. Studies evaluating the effects of human selection on genetic variation of plant populations were conducted in species, such as Polaskia chichipe [ 77 ], Escontria chiotilla [ 78 ], and P. In general, these studies have concluded that there is a slight reduction in genetic variation of silviculturally managed and cultivated populations when compared with wild populations. However, the opposite was recorded for Stenocereus stellatus [ 76 ] and S.
One explanation to this increased diversity proposed by the authors is the continuous replacement of individuals in plantations, as well as the inclusion of types of these species from other villages. Furthermore, the authors also argued that tolerance and caring for seedlings and juveniles as well as seed dispersal by humans and animals appeared to contribute to the maintenance of local genetic diversity.
In general, the methods used for characterizing the patterns of domestication conducted in Mesoamerica, are helpful in the analysis of general patterns of plant domestication, since the selection associated with handling provides similar "measurable" results that allow researchers to visualize and investigate the human cultural causes of management and artificial selection on plants and their results.
Even though studies on domestication of Brazilian plant species using ethnobotanical and evolutionary approaches are scarcer than in Mesoamerica, studies in the Amazon region have documented that fruit trees include a large number of species under different degrees of domestication, especially at incipient stages [ 11 ]. According to Clements et al. Peach palm , Paullinia cupana Kunth. Brazilian chestnut tree , and Theobroma grandiflorum Willd. Another important case study is that on Spondias tuberosa Arruda which is pioneering in some study methods. Our studies found that individuals of S.
This conclusion is based on the fact that the S. Fruits can be found in various sizes and flavors in both managed and unmanaged areas, but in managed areas the fruits are significantly larger and tastier [ 15 , 80 ]. People maintain local phenotypic diversity in the fruit of S. Levels of genetic diversity are also well maintained in managed populations [ 81 ], which allowed to concluded that the local management practice of tolerance is strongly related to conservation of both morphological and genetic diversity of this plant species.
In the southern region of Brazil, Santos et al. Berg , finding phenotypic differences mainly in shape and color of the fruit between wild and managed populations and concluded that this species is in incipient domestication [ 82 ]. The studies referred to above are those that have started in Brazil documenting the use and management of plant species from the perspective of incipient domestication.
However, due to the ecosystem, biological and cultural diversity of Brazil, certainly the application of methods for studying domestication of plants developed in Mesoamerica may potentially show interesting points in common and those that are particularly different. However, it should be noted that for trees such as Crescentia spp. Considering the biological and cultural diversity of Brazil, studies on plant management and domestication should be intensified.
The Mesoamerican methods and models may be helpful for constructing a Brazilian framework to understand the dynamics of domestication guided by local Brazilian peoples. The increasing number of ethnobotanical studies conducted in the Northeastern region of Brazil, allows a favorable scenario to understand the processes of domestication of plants in semiarid areas as well as in the Amazon.
Studies during the s evaluated the morphological variation among wild relatives and domesticated plants and focused on the deepening of morphometric intraspecific analyses of populations with different management histories [ ]. Previously, morphological variations were evaluated among cultivated and wild relatives to address where the variations originated and why the process of domestication began.
The Origins Of Agriculture In The Lowland Neotropics (ePUB/PDF)
Since the s, the main interest shifted to the process of domestication itself, focusing the attention on how domestication occurs [ ]. From the s, there has been an increasing number of studies concerning the genetic variation of plant populations under different management forms [ ]. In the s, ethnobotany developed a close interaction with evolutionary genetics and ecology, allowing considerable advances to understand the process of domestication.
In such a context, ethnobotany has a crucial role to play for understanding the constellation of cultural aspects, motives and mechanisms of artificial selection and managed gene flow [ 21 ] put in practice by peoples to determine domestication of species and landscapes according to their constellation of purposes. Ethnobotanical studies of incipient domestication in Mesoamerica have focused mainly to analyze domestication as an ongoing process [ 17 , 34 , 37 , 38 , 40 ]. These studies try to answer questions such as what are the targets of artificial selection in a species?
How does the local cultural, economic and ecological factors influence the processes of domestication? What types of species are recognized locally?
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How are they perceived? Which are preferred and why? What are the main management practices locally used to direct artificial selection and gene flow? How different management forms determine different intensities of artificial selection? In this way, ethnobotany seeks to elucidate aspects related to the domestication as a holistic socio-ecological or bio-cultural process. The following questions are also priorities in further studies: What makes a plant likely to be chosen among other plants with similar potential use?
Why to invest effort in managing a species but not in others? There may be numerous motives influencing how the choice is directed; therefore studies focused on these issues are imperious, as stated by Cleveland et al. Nevertheless, we must highlight that such decision-making by selection agents is crucial, not only to improve our understanding of the process of domestication, but also because it is helpful to identify main potential resources, priorities for conservation issues and local solutions developed to decrease risk in those important plant resources.
In few years, ethnobotany has developed and improved its methodological framework which is now a valuable body of tools for testing hypotheses and developing theories to elucidate questions about interactions between people and plants [ ]. Interaction of ethnobotany with ecology, evolutionary genetics, and archaeology is nowadays a reality that has generated a research approach to understand the evolution of plants under domestication.
Comparing patterns of domestication with similar methods provides the opportunity to understand general and particular contextual factors influencing domestication of species and landscapes of peoples of the World. In the New World it is particularly important to conduct deeper analyses comparing processes now occurring in main centers of origin of agriculture such as Mesoamerica, the Andean region of Peru, Bolivia, Argentina and Ecuador, as well as regions exceptional because of their high biological and cultural diversity, as are the Brazilian Amazonia and the semi-arid caatinga.
It is a process involving nature and society and should be therefore studied through holistic approaches. Ethnobotany has played an important role documenting the main cultural and biological factors influencing artificial selection and other evolutionary processes guided by humans to domesticate species and landscapes in territories. Processes of domestication are alive throughout the world and understanding how currently operate is crucial to analyze factors that in the past conducted to the origin of agriculture.
But also, these studies provide key information for sustainable management of genetic resources for the future. The Mesoamerican methods and frameworks developed to analyze domestication are similarly applicable to understand the processes occurring in Brazil and vice versa. Therefore implementing research using similar methods should be emphasized in further studies in order to produce comparable information to understand general patterns of domestication.
Edited by: Byers DS.
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A summary of the subsistence, Volume one: environment and subsistence. Harlan JR: Crops and Man. Foundation for Modern Crop Science. Origins of Agriculture. Edited by: Reed CA. Flannery KV: The research problem. Gepts P: Crop domestication as a long-term selection experiment. Plant Breeding Reviews.