The Olmecs were the earliest known major civilization in Mexico following a progressive development in Soconusco. They lived in the tropical lowlands of south-central Mexico, in the present-day states of Veracruz and Tabasco. It has been speculated that the Olmecs derive in part from neighboring Mokaya or Mixe-Zoque. The Olmecs flourished during Mesoamerica's formative period, dating roughly from as early as 1500 BCE to about 400 BCE. Pre-

The beginnings of Olmec civilization have traditionally been placed between 1400 and 1200 BCE. Past finds of Olmec remains ritually deposited at El Manati shrine (near San Lorenzo) moved this back to "at least" 1600-1500 BCE. It seems that the Olmec had their roots in early farming cultures of Tabasco, which began between 5100 BCE and 4600 BCE. These shared the same basic food crops and technologies of the later Olmec civilization.  What is today called Olmec first appeared fully within the city of San Lorenzo Tenochtitlan, where distinctive Olmec features occurred around 1400 BCE. The rise of civilization was assisted by the local ecology of well-watered alluvial soil, as well as by the transportation network provided by the Coatzacoalcos River basin. This environment may be compared to that of other ancient centers of civilization: the Nile, Indus, and Yellow River valleys, and Mesopotamia. This highly productive environment encouraged a densely concentrated population, which in turn triggered the rise of an elite class. The elite class created the demand for the production of the symbolic and sophisticated luxury artifacts that define Olmec culture. Many of these luxury artifacts were made from materials such as jade, obsidian, and magnetite, which came from distant locations and suggest that early Olmec elites had access to an extensive trading network in Mesoamerica. The source of the most valued jade was the Motagua River valley in eastern Guatemala, and Olmec obsidian has been traced to sources in the Guatemala highlands, such as El Chayal and San Martin Jilotepeque, or in Puebla, distances ranging from 200 to 400 km (120-250 miles) away, respectively.  The state of Guerrero, and in particular its early Mezcala culture, seem to have played an important role in the early history of Olmec culture. Olmec-style artifacts tend to appear earlier in some parts of Guerrero than in the Veracruz-Tabasco area. In particular, the relevant objects from the Amuco-Abelino site in Guerrero reveal dates as early as 1530 BCE. The city of Teopantecuanitlan in Guerrero is also relevant in this regard.

Answer the following question by taking a quote from the article: How did they start
These shared the same basic food crops and technologies of the later Olmec civilization.