(1) Stratigraphy. When there is accurate excavation of a site, the undisturbed remains in any given level may fairly safely be assumed to be earlier than the remains in the levels that overlie it.
(2) Typology. The age of a given culture may sometimes be determined approximately when most of the objects representing it appear to be identical in type with objects found elsewhere in a culture which has been dated by other means.
(3) Geology. The relative age of different remains can often be ascertained by finding the relative age of the geological strata in which the remains occur, as in the case of a series of sedimentary deposits, or river terraces and raised beaches, marking former shorelines or flood levels in valleys at times when the mutual relation of land and water was different from that of the present.
(4) Palaeontology. The presence (with the human remains) of extinct or still existing species of animals (including marine and lacustrine fauna) frequently provides a fairly exact basis for dating the human remains, in terms of geological periods.
(5) Palaeobotany. The presence of plant remains furnishes a further basis for assigning associated human remains to certain geological periods.
(6) Climatic evidence. When the past record of major climatic sequences in an area is known, human remains can often be dated in terms of glacial advances and retreats or pluvial and dry periods, if the remains are found in deposits characteristic of such periods. The kinds of animals and plants found in association with the human remains frequently show whether the climate of the period in question was wet or dry or warm or cold. Thanks to the great progress which has recently been made in palaeobotany it is now possible to trace climatic fluctuations (as reflected by the immigration of new forest forms) through microscopic examination of pollen grains preserved intact for thousands of years in peat beds and elsewhere. Associated archaeological remains can thus often be referred with great accuracy to a given climatic phase.
There is considerable room for error in the use of each of these methods, unless the greatest care is exercised, but they are all sound in principle and in general they may be relied upon, particularly when one confirms another. The ideal system would make use of all the methods listed above, establishing for any area the sequence of climatic changes, earth movements and deposits, and using this as a chronological framework into which to fit the successive cultures, reconstructed on the basis of the stratigraphy of the archaeological remains. For very few regions has this been done.