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Earliest development of bilateral symmetry, mesoderm, head (anterior cephalization) and various gut muscles (and thus peristalsis) and, in the Nephrozoa, nephridia (kidney precursors), coelom (or maybe pseudocoelom), distinct mouth and anus (evolution of through-gut), and possibly even nerve cords and blood vessels. [8]
Chalcolithic (or "Eneolithic", "Copper Age") Ancient history (The Bronze and Iron Ages are not part of prehistory for all regions and civilizations who had adopted or developed a writing system.) Bronze Age; Iron Age; Late Middle Ages. Renaissance; Early modern history; Modern history. Industrial Age (1760–1970) Machine Age (1880–1945) Age ...
In the course of the 4th century a great change took place; the Lucanians (an Oscan people), who had been gradually extending their conquests towards the south, and had already made themselves masters of the northern parts of Oenotria, now pressed forwards into the Bruttian peninsula, and established their dominion over the interior of that ...
Extensive development of sponge reefs. 176 Ma First Stegosaurian dinosaurs. 170 Ma Earliest salamanders, newts, cryptoclidids, elasmosaurid plesiosaurs, and cladotherian mammals. Sauropod dinosaurs diversify. 168 Ma First lizards. 165 Ma First rays and glycymeridid bivalves. First vampire squids. [92] 163 Ma Pterodactyloid pterosaurs first ...
Human history or world history is the record of humankind from prehistory to the present. Modern humans evolved in Africa around 300,000 years ago and initially lived as hunter-gatherers.
The Rise of Bronze Age Society: Travels, Transmissions and Transformations. Cambridge University Press. ISBN 978-0521843638. Turner II, Christy G.; Ovodov, Nicolai D.; Pavlova, Olga V. (2013). Animal Teeth and Human Tools: A Taphonomic Odyssey in Ice Age Siberia. Cambridge University Press. ISBN 978-1-107-03029-9.
Based on a dataset of average population density of hunter-gatherer groups collected by Lewis R. Binford, which indicate a mean density of 0.1223 humans per km 2 and a median density of 0.0444 humans per km 2, the combined human population of Africa and Eurasia at the time of the LGM would have been between 2,998,820 and 8,260,262 people.
The ages of more recent layers are calculated primarily by the study of fossils, which are remains of ancient life preserved in the rock. These occur consistently and so a theory is feasible. Most of the boundaries in recent geologic time coincide with extinctions (e.g., the dinosaurs ) and with the appearances of new species (e.g., hominids ).