Content revised 1997
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1. Proterozoic (Precambrian) Eon 4.5b?-545m
2. Phanerozoic Eon 570m-present
   1. Paleozoic Era 545m-245m
      1. Cambrian Period 545m*-500m <
         *-This date was formerly thought to be about 570 million years ago. A dramatic revision in 1993 forced scholars to reconsider the speed at which changes occurred in the fauna of that period.
      2. Ordovician Period 510m-439m
      3. Silurian Period 439m-409m
      4. Devonian Period 409m-363m
      5. Carboniferous Period 363m-290m
      6. Permian Period 290m-245m
   2. Mesozoic Era 225m-65m
      1. Triassic Period 245m-146m
      2. Jurassic Period 208m-146m (dinosaurs &c.)
      3. Cretaceous Period 146m-65m (arborial prosimians)
   3. Cenozoic Era 65m-present
      1. Tertiary Period 65m-1.6m±1
         1. Paleocene Epoch 65m-57m
         2. Eocene Epoch 57m-35m
         3. Oligocene Epoch 35m-24m (evolution of apes &c.)
         4. Miocene Epoch 24m-5m (very earliest hominids appear at very end)
         5. Pliocene Epoch 5m-1.6m
      2. Quaternary Period 1.6m±1-present
         1. Pleistocene Epoch1.6m±-10t
            1. Lower Pleistocene 1.6m-7ht
               1. Günz Glaciation 1.4m-7ht (roughly = Nebraskan Glaciation?)
            2. Middle Pleistocene 7ht-125t
               Reversal of Earth's polar field about 7ht
               1. Mindel Glaciation 640t-3ht (roughly = Kansan Glaciation?)
               2. Riss Glaciation 265t-100t (roughly = Illinoian Glaciation?)
            3. Upper Pleistocene 125t-10t
               1. Würm Glaciation 70t-10t (roughly = Wisconsin Glaciation)
         2. Holocene Epoch 10t-present *
            *-Some geologists have proposed the term "Anthropocene" to differentiate a post-Holocene, present epoch in recognition of human effects upon the planet, from radioactivity attributable to atomic bomb testing through carbon dioxide build-up in the atmosphere. Although in unofficial use, the term has not (yet) been formally adopted by international conventions.

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Note: There is a traditional, if somewhat misleading, "three age" system that divides prehistory into three stone (or "lithic") ages plus the bronze age and the iron age. Despite its many faults, prehistorians continue to use these terms, even while universally complaining about the inconsistencies in this scheme, especially if applied outside Europe. Here is a reasonably modern version for reference. (Geological epochs are included, but are grayed to stress that they are geology, while this chart is about archaeology.)

1. (Middle Pleistocene Geological Epoch 7ht-125t)
   and
   (Upper Pleistocene Geological Epoch 125t-10t)
   1. Paleolithic ?-10t
      (Listings after 150t BC are for the Classical European assemblages, some rather local, others widely found across Eurasia.)
      1. Lower Paleolithic 2.5m?-150t
         1. Oldowan (pebble tools, beginning about 2.5m yrs ago) (More About the Oldowan)
         2. Lower Acheulean (= Abbevillian) 1.5m-450t (More About the Acheulean)
         3. Middle Acheulean 450t-150t
      2. Middle Paleolithic 150t-40t (Neanderthals)
         1. Upper Acheulean 150t-100t (More About the Acheulean)
            NB: "Upper Acheulean" can perhaps best be taken to represent almost an Acheulean-Mousterian transitional assemblage (sometimes referred to as Levalloisian). Some writers use the term "Acheulean" only for Lower Paleolithic [Lower and Middle Acheulean] industries, but tools of this kind continue to be made to the present.
         2. Mousterian 100t?-35t? (More About the Mousterian)
            
            NB: Effectively all Neanderthal technology was Mousterian, with examples widely found throughout the Old World.) (Levallois technique comes into general use.)
      3. Upper Paleolithic (Homo sapiens, beginning with "Cro-Magnons")
         1. Aurignacians 40t?-30t (thinner blades) (More About the Aurignacian)
            NB: In France a somewhat separate "Perigordian" tradition has been differentiated, roughly contemporaneous with the Aurignacian, but beginning about 1t years earlier. The earliest or "Lower" Perigordian [Perigordian I] phase is also called the Châtelperronian; at one site, St. Césaire, Neanderthal bodies have been found with this assemblage.
            (More About the Perigordian)
            (More About the Châtelperronian)
         2. Gravettians 30t-20t (Venus figures) (More About the Gravettian)
         3. Solutreans 20t-17t (clay modeling, laurel blades) (More About the Solutrean)
         4. Magdalenians 17t-9t (reindeer) (More About the Magdalenian)
         5. Hamburgians & Ahrensburgians 13t-8t (North Germany) (More About the Hamburgian) (More About the Ahrensburgian)
2. (Holocene Geological Epoch 10t-present)
   1. Mesolithic 10t-9t (Europe only)
      *-NB: The term "Epipaleolithic" is sometimes used for post-Pleistocene, pre-Neolithic, microlithic assemblages. The most often mentioned is perhaps the Azilians, with the type site as Mas d'Azil in southern France. (More About the Azilians)
   2. Neolithic 9t-5t
      (More About Ground Stone Tools)
   3. Chalcolithic (pronounced "kalko-LITH-ic"; = Copper Age = Eneolithic) 5t-3t
   4. Bronze Age 3t-1t
   5. Iron Age 1t till arrival of the Romans
      (or, in areas outside the Roman Empire, till the 4th to 6th century A.D., or, for some writers, till the present)

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