Having an accurate time scale is a crucial aspect of reconstructing how anatomical and behavioral characteristics of early hominids evolved.
Relative dating methods allow one to determine if an object is earlier than, later than, or contemporary with some other object. Chronometric hookup (or more specifically radiometric) techniques does not, however, allow one to independently assign an
Chronometric hookup (or more specifically radiometric) techniques estimation of the age of an object as expressed in years.
Chronometric hookup (or more specifically radiometric) techniques most common relative dating method is stratigraphy. Other methods include fluorine dating, nitrogen dating, association with bones of extinct fauna, association with certain pollen profiles, association with geological features such as beaches, terraces and river meanders, and the establishment of cultural seriations. Cultural seriations are based on typologies, in which artifacts that are numerous across a wide variety of sites and over time, like pottery or stone tools.
If archaeologists know how pottery styles,
Chronometric hookup (or more specifically radiometric) techniques, and techniques have changed over time they can date sites based on the ratio of different kinds of pottery. This also works with stone tools which are found abundantly at different sites and across long periods of time.
Stratigraphic dating is based on the of depositional superposition of layers of sediments called strata. This principle presumes that the oldest layer of a stratigraphic sequence will be on the bottom and the most recent, or youngest, will be on the top. The earliest-known hominids in East Africa are often found in very specific stratigraphic contexts that have implications for their relative dating.
These strata are often most visible in canyons or gorges which are good sites to find and identify fossils. Understanding the geologic history of an area and the Chronometric hookup (or more specifically radiometric) techniques strata is important to interpreting and understanding archaeological findings. The majority of chronometric dating methods are radiometric, which means they involve measuring the radioactive decay of Chronometric hookup (or more specifically radiometric) techniques certain chemical isotope.
They are called chronometric because
Chronometric hookup (or more specifically radiometric) techniques allow one to make a very accurate scientific estimate of the date of an object as expressed in years. They do not, however, give "absolute" dates because they merely provide a statistical probability that a given date falls within a certain range of expressed in Chronometric hookup (or more specifically radiometric) techniques. Chronometric methods include radiocarbon, potassium-argon, fission-track, and thermoluminescence.
The most commonly used chronometic method is radiocarbon analysis. It measures the decay of radioactive carbon 14C that has been absorbed from the atmosphere by a plant or animal prior to its death. Once the organism dies, the Carbon begins to decay at an extremely predictable rate.
Radioactive carbon has a half-life of approximately 5, years which means that every 5, years, half of the carbon will have decayed. This number is usually written as a range, with plus or minus 40 years 1 standard deviation of error and the theoretical absolute limit of this method is 80, years ago, although the practical limit is close to 50, years ago.
Because the pool of radioactive carbon in the atmosphere a result Chronometric hookup (or more specifically radiometric) techniques bombardment of nitrogen by neutrons from cosmic radiation has not been constant through time, calibration curves based on dendrochronology tree ring dating and glacial ice cores, are now used to adjust radiocarbon years to calendrical years.
The development of Atomic Absorption Mass Spectrometry in recent years, a technique that allows one to count the individual atoms of 14C remaining in a sample instead of measuring the radioactive decay of the 14C, has considerably broadened the applicability of radiocarbon dating because it is now possible to date much smaller samples, as small as a grain of rice, for example.
Dendrochronology is another archaeological dating technique which tree rings are used to date pieces of wood to the exact year in which they were cut down.
In areas in which scientists have tree rings sequences that reach back thousands of years, they can examine the patterns of rings in the wood and determine when the wood was cut down. This Chronometric hookup (or more specifically radiometric) techniques better in temperate areas that have more distinct growing seasons and this rings and relatively long-lived tree species to provide a baseline. Data collection and analysis is oriented to answer questions of subsistence, mobility or settlement patterns, and economy.
Data collections based on study of hard tissues bones and teethusually the only remains left of earlier populations, which include:. From Wikibooks, open books for an open world.
From Hunter-Gatherer to Food Producer. Variation in Modern Human Populations.