Most common evolutionary dating methods
Dendrochronology is useful in measuring tree rings from zero to 12,000 years old.If dated fossil are found near the hominid bones it can be said that both species lived around the same time, and hence the homonids samples can be dated. t very good for very old specimens; fossils were often found with no volcanic deposits present; and the use of other fossils such as ancient hyenas or antelope wasn’t always so reliable for pinpoint dating because the animals often they lived for a long time on the evolutionary timeline.[Source: Kenneth Weaver, National Geographic, November 1985 [┹] Websites and Resources: Modern Human Origins ; Talk Origins Index talkorigins.org/origins ; Hall of Human Origins American Museum of Natural History amnh.org/exhibitions ; Time Space Chart Hominid Fossils Pictures msu.edu/~heslips ; Smithsonian Human Origins Program edu ; Wikipedia article on Human Evolution Wikipedia ; Becoming Human University of Arizona site ; Human Evolution Images ; Hominid Species ; Institute of Human Origins edu ; Paleoanthropology Link ; Britannica Human Evolution britannica.com/EBchecked/topic/275670/human-evolution ; Modern Human Origins ; Human Evolution ; Paleoanthropology and Evolution Links unipv.it/webbio/dfpaleoa ; National Geographic Atlas of the Human Journey genographic.nationalgeographic.com/genographic/atlas ; Yale Peabody Museum edu/exhibits/fossils ; Humin Origins Washington State University wsu.edu/gened/learn-modules ; Book: The Human Evolution Source Book In the old days Carbon 14, the age of volcanic deposits and age of other fossils found with specimens were the main dating method for dating early man fossils. These days scientists have a whole host of dating methods at their disposal.Once a hominid fossil has been discovered it can be dated by two main ways: 1) by analyzing the volcanic ash around the fossils; 2) by analyzing the other fossils found around the newly discovered hominid bones. If the ash is older than 1.6 million it can be dated with the potassium-argon method, which dates items by measuring chemical decay.Each volcanic eruption has a unique "fingerprint" and sometimes they scatter ash over a vast area.[Source: Time magazine, December 18, 2007] Sometimes geologists can help date objects by measuring the amount of rain wear in cracks, alluvial deposits by streams and glaciers and layers of silt in lakes.Lichenometry is useful in measuring lichens from 100 and 9,000 years old.They include amino acid racemization, useful in measuring shells and other bicarbonates between 500 and 300,000 years old, and obsidian hydration, used to measure natural glass between 500 to 200,000 years old.
In analyzing the other fossils found around the newly discovered hominid bones.
Many fossils of the other creatures, such as ancient elephants and rhinos, have been dated before at other locations using the volcanic ash, potassium-argon method described above.
The geomagnetic polarity timescale method is useful in measuring minerals between 780,000 and 200 million years old in places where there are no volcanic deposits are formed.
This method dates objects by measuring the periodic reversals of the north and south magnetic poles, which have occurred at known times and rates.
A dating method used by Richard Bailey at Oxford University measures the amounts of radiation absorbed by sand grains in and around a bone specimen by measuring radioactive isotopes in the sand and comparing that to a sophisticated radiation transport model using data from a CT scan of the specimens.The age of the specimen is determined by calculating the yearly rate at which radiation had been absorbed by the sand grains.