Related by context. Frequent words. (Click for all words.) 66 Cretaceous Period 65 Late Cretaceous 64 Carboniferous 63 Pleistocene 63 glaciation 61 Precambrian 59 Quaternary 59 Ordovician 59 interglacial 59 Pliocene 58 Cretaceous 58 megafauna 58 multicellular 57 mass extinctions 56 Mesozoic 56 Eocene 56 fossils 55 volcanism 55 Tiktaalik 55 Ardipithecus 55 prehistory 54 tetrapods 54 Neandertals 54 dinosaurs roamed 54 Paleozoic 53 Homo sapiens 53 fossil 53 diatoms 53 landforms 53 Little Ice Age 53 vertebrates 53 Archaeopteryx 53 taxa 53 anatomically modern 53 eukaryotes 53 domestication 52 Australopithecus 52 theropods 52 hominid 52 hominids 52 Holocene 52 vertebrate 52 speciation 52 plate tectonics 52 sauropods 52 Proterozoic 52 mass extinction 51 eukaryotic 51 mammoths 51 palaeontologists 51 extinctions 51 Triassic 51 single celled organisms 51 dinosaurs 51 fossilized 51 morphological 51 Neolithic 51 mammals 51 Medieval Warm Period 50 lake sediments 50 tyrannosaur 50 prehistoric 50 Oligocene 50 diatom 50 radiocarbon 50 fossilized remains 50 palaeontology 50 archaea 50 Homo erectus 49 radiocarbon dating 49 Paleolithic 49 Homo habilis 49 plesiosaur 49 lineages 49 hunter gatherers 49 Devonian 49 morphology 49 nitrogen fixation 49 carnivorous dinosaurs 49 isotopic 49 cyanobacteria 48 sedimentary rock 48 biota 48 paleontologists 48 biogenic 48 coelacanth 48 embryogenesis 48 sediments 48 abundances 48 Neanderthals 47 melanosomes 47 Archaea 47 evolutionary 47 overhunting 47 geologic 47 crustal 47 desiccation 47 Jurassic 47 continental drift 47 woolly mammoths 47 atmospheric carbon dioxide