Related by context. Frequent words. (Click for all words.) 72 Cretaceous Period 64 interglacial 61 Pliocene 61 Pleistocene 61 Little Ice Age 60 glaciation 60 Late Cretaceous 58 Eocene 57 mass extinctions 57 Medieval Warm Period 55 Holocene 55 Ordovician 55 Quaternary 55 Ice Age 55 Carboniferous 55 dinosaurs roamed 55 Cretaceous 52 anatomically modern 52 Mesozoic 51 mass extinction 51 Fertile Crescent 51 El Ninos 51 Triassic 51 Neandertals 51 megafauna 50 Precambrian 50 Homo sapiens 50 continental drift 50 epochs 50 terrestrial ecosystems 49 sediment cores 49 Australopithecus 49 fossils 49 hominins 48 Homo erectus 48 fossil 48 plate tectonics 48 volcanism 48 millenniums 48 PETM 48 radiocarbon 48 Australopithecus afarensis 48 fossilized remains 48 Oligocene 47 Weddell Sea 47 dinosaurs 47 supernova explosion 47 hominid 47 atmospheric carbon dioxide 47 sunspot activity 47 Homo habilis 47 multicellular organisms 47 temperate regions 47 radiocarbon dating 47 lithosphere 47 Ellesmere Island 47 lake sediments 47 millennia 47 hominids 47 Miocene 46 geologic 46 equinoxes 46 glacial melt 46 biome 46 Paleolithic 46 mammoths 46 landmasses 46 Paleozoic 46 prehistory 46 Jurassic 46 gyre 46 temperate zones 46 Neanderthals 46 substorms 46 prehistoric 46 Mayan civilization 45 multicellular 45 Tiktaalik 45 mid latitudes 45 vertebrate species 45 journal Geology 45 atmospheric CO2 45 vernal equinox 45 tropics 44 Ardipithecus 44 volcanic eruptions 44 diatom 44 biodiversity hotspots 44 geomagnetic 44 Archaeopteryx 44 common ancestor 44 woolly mammoths 44 extinctions 44 Mesoamerica 44 diatoms 44 CO2 concentrations 44 greenhouse warming 44 single celled 44 Greenland glaciers 44 landforms 44 migrations