the lives and achievements of actual personages. He also believed that the southern centers such as Copán and Quiriguá had been united in the Classical period under what he termed the "Old Empire". This empire mysteriously collapsed, but the remnants later migrated to the northern sites (such as Chichen Itza) to form a "New Empire". It is now generally accepted that at no time was the Maya region united under a single polity, but rather that individual "city-states" maintained a somewhat independent existence, albeit one with its fluctuating conquests and local subservience to more dominant centers. In support of his view, Morley devised a 4-tier classification system of relative importance, which he ascribed to all of the then-known main Maya sites (about 116); many more sites are now known, and his classification system is now seen as an arbitrary one, contradicted in places by the sites' texts which can now be (substantially) read. Other ideas Morley put forward include the proposal that the ancient Maya were the first in Mesoamerica to domesticate maize (Zea mays ssp. mays), with the wild variety known as teosinte being its progenitor. Recent genetic studies have shown Morley to be largely correct in this, although the beginnings of its domestication (12,000 to 7,500 years ago) pre-dates the establishment of anything resembling Maya society. In general, Morley held that the ancient Maya had been the pre-eminent civilization of Mesoamerica, from which other cultures had drawn their influences. It is now accepted that other societies (such as the Zapotec and Olmec) preceded that of the Maya and the influences—such as development of writing and the Mesoamerican calendars—were rather the other way around; even in the later stages of Maya history, their region came under significant influences drawn from central Mexico, such as the Toltec "invasion". However, the Maya did also exert a widespread influence over neighboring contemporary cultures, one which was significant and not to be overlooked. Maya writing In common with most other Maya scholars, Morley was particularly interested in the mysterious nature of the Maya script. The essentials of the calendric notation and astronomical data had been worked out by the early 20th century, and by the 1930s John E. Teeple had solved (with Morley's encouragement) the glyphs known as the "Supplementary Series", proving that these referred to the lunar cycle and could be used to predict lunar eclipses. However, the bulk of the texts