Related by context. Frequent words. (Click for all words.) 64 multicellular 59 mass extinctions 57 mass extinction 57 glaciation 57 Late Cretaceous 57 megafauna 57 eukaryotes 56 dinosaurs 55 Archaeopteryx 55 supernova explosion 55 speciation 55 single celled organisms 55 single celled 54 Precambrian 54 Homo sapiens 54 vertebrate 53 Pleistocene 53 volcanism 53 Ordovician 53 evolutionary 53 plate tectonics 53 Cretaceous 52 mammals 52 fossils 52 anatomically modern 52 diatoms 51 Australopithecus 51 tetrapods 51 Mesozoic 50 hominid 50 vertebrates 50 tyrannosaurs 50 Triassic 50 fossil 49 prehistory 49 primordial soup 49 Neandertals 49 Homo erectus 49 theropods 49 mammoths 49 archaea 48 hominids 48 vertebrate species 48 prehistoric 48 pterosaurs 48 extinctions 48 common ancestor 48 supernova explosions 48 lineages 48 Pliocene 48 Eocene 48 Homo habilis 48 scientists theorize 47 Holocene 47 chemical reactions 47 organisms 47 supernovae 47 domestication 47 organic molecules 47 fossilized remains 47 coelacanth 46 plesiosaur 46 evolution 46 flowering plants 46 sauropod 46 sauropods 46 Little Ice Age 46 quark gluon plasma 46 melanosomes 46 taxa 46 atmospheric carbon dioxide 46 pterosaur 46 eukaryotic 46 epochs 46 mammal 46 morphological 46 humans 46 mammalian 46 magnetar 45 Big Bang 45 Richard Feynman 45 arthropods 45 homo sapiens 45 lifeforms 45 Fertile Crescent 45 organism 45 supernova 45 evolutionary biologists 45 arthropod 45 fossilized bones 45 phylogeny 45 epoch 45 comets 45 diatom 45 dinos 45 PETM 45 landforms 44 hydrothermal vents 44 Homo floresiensis 44 Paleolithic 44 supernovas