a gas, it is released. The ratio of argon-40 released to potassium-40 still present allows for a date to be assigned to objects near the sample. However, due to potassium's high half-life (1.3 billion years), it is only useful as a dating technique for finds older than 500,000 years old. Also, it is only useful where volcanic activity existed. Both these methods have error margins, ranging from a few thousand years in carbon-14 dating to tens of thousands of years, or more, for potassium-argon dating. However, thanks to scientific breakthroughs, these two processes can be used with reasonable security in establishing a time for fossils.Our farthest believed ancestor is believed to be Australopithecus afarensis. This species, which lived between three and four million years ago, is believed to be the first real hominid because it is the oldest, and "most primitive of any definite hominid form thus far found."(Turnbaugh, 281) Evidence from fossilized footprints, as well as pelvic and leg bones which were similar to modern hominids, led scientists to believe that they could walk upright. Its teeth resembled more those of primates, due to their large size. Its skull capacity ranged from 350 to 500 cm3. This species, though it had some hominid characteristics, was still more like an ape. Its face protruded outwards near the mouth region, and it did not have a definable chin. Finally, their craniums had large, protruding ridges over the eyes.Another important being in the human timeline is Australopithecus africanus. Many scientists believe that it is the next in the sequence leading to man, however, a few believe that it belongs to a lineage on its own. Africanus fossils have been dated back to the time period between two and three million years ago. It had a greater body size than Afarensis, and a skull volume ranging between 420 and 500 cm3. It averaged a little higher in height than the 3 to 5 feet believed for Afarensis. Its jaws also ...
