3 years ago

O Homem seguiu as plantas ou as plantas seguiram o Homem?

O Homem seguiu as plantas ou as plantas seguiram o Homem?


DID MAN FOLLOW PLANTS OR DID PLANTS FOLLOW MAN TRACKS OF PREHISTORIC MAN AND WAYS OF CONTACT IN THE AMERICAS, ACCORDING TO CULTIVATED PLANTS. CASE-STUDY – MAIZE Introduction The colonization of the Americas by prehistoric man still provokes controversy, above all the date of man’s first arrival from Asia (Neves et al, 1989;Pena et al, 1989; Prous, 19889; Roosevelt, 1996). Independent from when this happened, as soon as man stepped on American soil, he began to migrate and colonize the country, from the extreme north to the south of the continent. Populations, traditions and ethnic groups flourished and started to spread over time and space. To track down these “internal” migrations, depends on actual evidence, starting with surviving populations from the first inhabitants, as well as on historical data from the last 500 years and on archaeological evidence (Harlan, 1975). Approx. 8.000 years ago, after an initial period of settling down some species were domesticated or semi-domesticated by man, and many of them constitute the basis of the crops which feed us today. Prospective species like maize, tomatoes, beans, peanuts and manioc, among others began to be grown, were domesticated from their wild ancestors by man. (Harlan, 1971; 1975; Gepts & Debouck, 1991). These domesticated plants were distributed by man from where he started out and when Europeans arrived in the 15 th century, the principal domesticated species of the new world had already begun to spread over the American continent. This is the case of maize, which the colonizers discovered as being grown in the three Americas, in the high latitudes of the two hemispheres as well as on sea level or up in high altitudes, reflecting its genetic diversity to cover such a large range of different environments. This diversity may partly be explained by the value this plant had and still has as the staple food for the majority of the American populations. Maize was regarded by many cultures as something sacred and during its course of evolution and dissemination was selected because of the characteristic environmental factors where it would grow and by proper man according to his cultural traditions, his tastes and uses, ranging from the preparation of food and drink to decoration. These natural and artificial selections of cultivated plants caused a series of variations/local breeds often correlated directly to specific human groups. Thus, analyzing different local variations of a given cultivated species, a connection between these might be claimed, determining those variations with a major or minor affinity. When geographical specifications are added, a topographical relationship between samples can be established. Furthermore, including archaeological data, a time dimension is added, pointing out what characterizes the given sample, where it is located and when this happened (Freitas et al, 2003). FUMDHAMentos VII - Fábio Freitas et alii 109

Objective We are going to present possible roads of diffusion for maize, in ancient times, and, parallel to that, possible ways of migration and contact of peoples in the past. Materials and Methods For this paper we analyzed directly 45 specimens of traditional and indigenous maize from different locations in Brazil and Paraguay, also 7 archaeological samples from caverns situated in the Peruaçu valley – Minas Gerais – Brazil, with ages varying between 1.100 and 560 year BP. We included data from literature, with samples from the area where maize originated, in Mexico and Guatemala and specimens from the Cordilleras, three of which were archaeological (with ages varying between 4.500 and 400 years BP). (Goloubinoff et al, 1993) From each sample a segment of genetic material (DNA) was extracted. The method applied was the genomic extraction using CTAB, with a secondary purification as reported by Allaby et al (1997), where the analyzed target sequence belongs to gene Adh2 (Freitas et al, 2003, Bustamante, 2005). The DNA segments thus obtained were then sequenced and compared by Network permitting to identify the mutations which took place in each sequence during the evolution of maize (Allaby & Brown, 2000; Freitas, 2001; Bustamante, 2005). Results and discussion In the first place the analysis showed that maize has got a high degree of genetic diversity. Generally speaking, all sequences of the samples fluctuate within three principal pattern groups, one of them being the “simple” type, the older one, the two others being more complex and more recent. These denominations are due to its particular genetic properties. It is interesting to note that these patterns show a specific geographical distribution (figure 1) and one of the patterns, the most primitive, (sample in white colour in the figure) was basically restricted to the highlands, along the Cordilleras, while the other two (blue and red in the figure) are predominant in the low regions (figure 1). This strongly indicates that distinct types of maize came from Central America to South America and, which is more, by different routes. The first type of maize entering South America was of the simple kind, a fact which is reinforced by the archaeological samples of the study, where this type is exclusively present in samples encountered in Peru, with ages of approx. 4.500 years BP (Goloubinoff et al, 1993). Apparently this type spread over the entire Andean region. FUMDHAMentos VII - Fábio Freitas et alii 110

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