Potassium argon dating hominids
"I have previously regarded Omo II as an archaic or primitive H. sapiens, which would make them the same species," Stringer said. "Regardless of how Omo II is classified, " he continued, "I don't consider it surprising to find two different morphologies existing at the same time.
"If Omo I and II do belong together, the variation in the population is greater than I expected, but given what we see in larger fossil samples from other regions, we may need to accept that African populations showed large [physical-form] variation at this time." Everyone agrees that the Omo II cranium is more primitive than the Omo I skull in many features, Fleagle said. We know that Homo sapiens and Neandertals existed in Europe at the same time and that in the early Pleistocene [epoch] there was diversity of early hominid morphologies [or body forms].
If archaeologists know how pottery styles, glazes, 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 principle 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.
They do not, however, give "absolute" dates because they merely provide a statistical probability that a given date falls within a certain range of age expressed in years.
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.
The remains of Omo I and Omo II were buried in the lowest sediment layer, called Member 1, of the 330-foot-thick (100-meter-thick) Kibish rock formation near the Omo River.
In addition to GPS, more advanced dating techniques have also been developed.