Types and stages of dating
Since then the molecular data and a steady trickle of new hominin fossil finds have pushed the earliest putative hominin ancestry back in time somewhat, to perhaps 8–6 mya., based on a cranium from of Chad in north-central Africa.
Announced in 2002, this specimen is dated to the period between 7 and 6 mya.
Instead, human evolution has been throughout its long history a matter of experimentation, with new species being constantly spawned and thrown into the ecological arena to compete and, more often than not, become extinct.
Viewed this way, is simply the last surviving twig on a vast and intricately branching bush, rather than the sole occupant of a summit that has been laboriously climbed and, by extension, somehow earned.
The molecular clock concept is based on an assumed regularity in the accumulation of tiny changes in the genetic codes of humans and other organisms.
Use of this concept, together with a reanalysis of the fossil record, moved the estimated time of the evolutionary split between apes and human ancestors forward to as recently as about 5 mya.
In general, they were relatively small-bodied, with large chewing teeth but reduced (sometimes highly reduced) canine teeth.
However, they also retained many reminders of their tree-dwelling ancestry, especially their rather long arms, short legs, narrow shoulders, and long grasping extremities.
may have originated as early as about 2.8 mya, though the record during this time is tantalizingly fragmentary.
A variety of incomplete or broken fossils from the period between about 2.5 and 2.0 mya have been placed in the category of “early .
The most remarkable aspect of this skull is the broadness and flatness of its face—something previously associated with much more recent hominins—in conjunction with a smaller, ape-sized braincase.
This specimen also has small canine teeth compared with those of apes, thus aligning it with the hominins in an important functional regard.