Related by context. Frequent words. (Click for all words.) 63 Cretaceous Period 62 interglacial period 59 Late Cretaceous 58 Cambrian explosion 58 interglacial 56 Pleistocene era 55 Little Ice Age 55 Younger Dryas 54 glaciation 54 Fertile Crescent 54 marine sediments 53 trilobites 53 Paleocene 52 H. erectus 52 atmospheric methane 52 Quaternary 52 Eocene 52 Cretaceous 52 Burgess Shale 51 supercontinent 51 Carboniferous 51 dinosaurs roamed 51 microfossils 51 vertebrate species 51 fossil 51 Ordovician 51 Pleistocene 50 Medieval Warm Period 50 Mesozoic 50 mass extinctions 50 terrestrial ecosystems 50 lake sediments 50 fossilized remains 50 Pliocene 49 volcanism 49 stromatolites 49 fossils 49 Homo sapiens 49 temperate regions 49 continental crust 48 diatom 48 lavas 48 baleen whales 48 prehistory 48 glacial melt 48 hominins 48 species extinctions 48 degrees Fahrenheit warmer 48 mass extinction 48 megafauna 48 preindustrial 48 oceanic crust 48 Precambrian 48 marine reptiles 47 multicellular organisms 47 subtropical regions 47 tyrannosaur 47 genus Homo 47 foraminifera 47 geologic 47 millennia 47 prehistoric 47 sediment cores 47 Antarctic ozone 47 hadrosaur 47 Oligocene 47 evolutionary adaptation 47 solar nebula 47 mammal species 47 aridity 47 Paleolithic 47 coprolites 47 biogeography 47 millenniums 46 classical antiquity 46 marine invertebrates 46 extinctions 46 biodiversity hotspots 46 Lower Cretaceous 46 Ardipithecus 46 tyrannosaurs 46 Poinar 46 Neandertals 46 genetic variability 46 ocean acidity 46 ocean ridges 46 mammals 46 lineages 46 continental drift 46 temperate zones 46 Neolithic 46 #BC [003] 46 theropod 46 crocodilians 46 anatomically modern 46 Mesoamerica 45 epochs 45 diatoms 45 paleontological 45 CO2 concentrations 45 mammal