Related by context. Frequent words. (Click for all words.) 64 Cretaceous Period 58 Late Cretaceous 56 interglacial 54 Ordovician 54 Pliocene 53 Cretaceous 53 Carboniferous 53 glaciation 52 mass extinctions 50 Triassic 50 Quaternary 49 Holocene 49 Little Ice Age 49 Eocene 49 mass extinction 49 Oligocene 49 Lower Cretaceous 48 Pleistocene 48 Precambrian 47 dinosaurs roamed 46 Medieval Warm Period 46 supernova explosion 46 Proterozoic 46 multicellular 46 anatomically modern 45 Paleozoic 45 volcanic eruptions 45 megafauna 44 volcanism 44 Devonian 44 Australopithecus afarensis 44 marine sediments 44 Mesozoic 44 Australopithecus 44 lake sediments 44 El Ninos 44 epochs 43 Ann Thorac Surg 43 Homo habilis 43 sedimentary rock 43 Article PubMed ISI ChemPort 43 multicellular organisms 43 trilobites 43 sedimentary rocks 42 Ardipithecus 42 terrestrial ecosystems 42 Article PubMed ChemPort 42 Tambora 42 hadrosaur 42 influenza pandemics 42 Mentalist CBS #.# 42 PETM 42 #BC [003] 42 sediments 42 JAMA. 42 Jurassic 41 Ice Age 41 geologic 41 Archaeopteryx 41 magmatic 41 extinctions 41 basalts 41 Silurian 41 Uranium mineralization 41 Sassanid 41 Ming Dynasty #-# 41 Fertile Crescent 41 ca. 41 Miocene 40 species extinctions 40 Grimsvotn 40 millenniums 40 fossilized remains 40 tetrapods 40 prehistoric 40 Archean 40 Cancer Res 40 genus Homo 40 geologically 40 atmospheric carbon dioxide 40 Han Dynasty 40 retreating glaciers 40 preindustrial 39 Homo erectus 39 #-# [015] 39 millennia 39 Homo sapiens 39 oceanic crust 39 radiocarbon 39 atmospheric CO 39 hominids 39 mammoths 39 Posted -# sec 39 hominins 39 Neolithic 39 lavas 39 fossils 39 plesiosaur 39 dinosaurs 39 hominin 39 crustal