* In the last few years the Out Of Africa theory (modern humans originated solely in Africa) has received stiff competition from the Multi Regional theory. Namely that waves of human species have left Africa since we diverged from chimpanzees 4 million years ago and that our ancestors are from all the homo-inhabited regions of the world to a greater or lesser extent.
* Neanderthals and Denisovans are 2 known species that certainly inhabited much of the world (apart from the Americas) from around 2/300,000 to 50,000 years ago.
* We certainly bred with Neanderthals and Denisovans, some of us contain up to 4% of their DNA.
* Mammals generally take about 5 million years before they evolve far enough to be reproductively isolated. Of course before then there can still be breeding problems, for which there is evidence of in our breeding with the aforementioned.
* DNA from human skeletons several hunreds of thousands of years old can still be analysed.
* Mitochondrial DNA is passed by mothers only and so undergoes very little mutation. So it provides a stable and valuable signature for detecting ancient affinities between species/sub-species.
* By analysing the variation within genes certain characteristics can be interpreted like population size (eg; there were very few Denisovans) and that there are as yet unidentified species that humans have inherited from.
* Neanderthals possessed the FOXP2 gene known to be central in human speech.
* One of the oldest known oral traditions has evidence to verify a story from around 30,000 years ago: that Australian aboriginees brought the palm tree seeds with them from the north. See: http://www.abc.net.au/news/2015-04-03/aboriginal-legend-palm...
Forgive any errors in this amateur homework report.