The Romans believed that the species of animals, including humans, were spontaneously generated from the materials of the Earth, because of which the Latin word "mater", "mother", descends to English-speakers as matter and material. In Lucretius the Earth is a mother, Venus, to whom the poem is dedicated in the first few lines. She brought forth humankind by spontaneous generation. Having been given birth as a species, humans must grow to maturity by analogy with the individual. The different phases of their collective life are marked by the accumulation of customs to form material civilization: