Some Useful Info on Human Evolution
There is a wealth of paleontological, archaeological/anthropological and genetic (primarily tracking Mitochondrial DNA) regarding the origins of Primates, the human species, and how humans spread around the world.
some links:
The National Geographic Foundation
http://www.ornl.gov/sci/techresources/Human_Genome/elsi/humanmigration.shtml
http://www.sciencedaily.com/releases/2010/01/100119154710.htm
http://anthro.palomar.edu/earlyprimates/first_primates.htm
the main points regarding the evolution of primates and the later evolution of the Human species, is that it is theorized that all primate species would have evolved from a prevalent common species of mammal that was adapting to the evolution and proliferation of large broad-leafed trees something like 185 million years ago when the landmasses on earth were locked together in the super continent Pangaea. The Proto-Primates were squirell like mammals that were evolving to take advantage of their environment by taking to these new trees: likely for new food sources and for safety from ground based predators.
As the continents drifted apart, these proto primates would have become isolated and this is where mutations in a species become more pronounced as the breeding groups become smaller. These Proto-primates developed along parallel paths leading to the diversity of primate life we see today.
On the continent of Africa, where our ancestors evolved, there have been a number of major environmental changes. It’s gone through periods where all of the contient would have contained lush tropical jungles, followed by periods of desertification (such as currently). These changes in the environment favor mutations in a species that are best able to adapt.
Essentially, geographic and environmental factors lead to some primates being better suited for life on the ground more than in trees, as they would have needed to be able to forage further across land to get food. This travel from group to group of trees, favored the primates with physical musations that made such travel easier and more efficiently (bipedal travel), as well as the changes in their brains that allowed them to begin to start communicating and organizing themselves more efficiently. Our ancestors were the primates that were better at this than other primates that may have been also evolving in a similar way (such as chimpanzees and gorillas).
eventually the primates that were our common ancestors evolved to the point of being what we recognize as human beings, and began to migrate further afield, populating the rest of the world
there is an excellent interactive feature online : http://www.bradshawfoundation.com/journey/
that describes the migritory history of humanity as discovered by studying Mitochondrial DNA.
