Homo sapiens sapiens is the scientific name given to modern humans. We are members of the genus Homo and family Hominidae. All other members of the Homo genus (such as Neanderthals) are now believed to be extinct.
The timeline of human evolution can be pieced together through the fossil record, but parts of it are unclear because fossil specimens are rare, and this leads to some uncertainty about some of the details. The changes are also not sharp because evolution is a process of very gradual changes over millions of years.
The following is an attempt to summarise the major timeline transitions, beginning with the ancestors of the Homo genus: Australopethicus.
Australopethicus ramidus lived from around 5.8 to 4 million years ago. This was a primitive Hominid, but it may have walked upright.
Australopethicus afarensis lived from around 4 to 2.7 million years ago. Fossils from over 300 individuals of this species have been found, including the famous Lucy'. It walked upright and may be the ancestor of the later Homo genus.
Australopethicus africanus lived from around 3 to 2 million years ago. It was similar to A. afarensis, and is also a likely candidate for being the ancestor of Homo.
Australopethicus robustus lived from around 2.3 to 1 million years ago. It was similar to A. afarensis, but had a thicker skull.
The oldest Homo species was probably Homo habilis who lived between 2.5 and 1.5 million years ago. Homo habilis remains have been found near stone tools, hence the name, which means handy man'.
Homo erectus was a cousin of Homo habilis, and live 2 million years ago to around 50,000 years ago. This species had a larger brain than Homo habilis, and was believed to be the first Homo species to migrate, and the first to use fire.
This species had been thought to have been extinct for around 300,000 years, but recent finds place them in Java only 50,000 years ago, which means they shared the planet with Homo sapiens. Java Man' was the first known fossil specimen.
HOMO SAPIENS (ARCHAIC)
Homo sapiens is also known as Homo Heidelbergensis and lived around 500-200,000 years ago. Similar to Homo erectus, Heidelbergensis had a larger skull and was as tall as modern humans and more muscular. Heidelbergensis diverged into two groups: the (now extinct) Neanderthal, and Homo sapiens sapiens.
There are two major schools of thought about the origins of Homo sapiens and their descendents Homo sapiens sapiens, which appeared around 130-150,000 years ago in Africa, and were also present in the Near East earlier than 90,000 years ago.
The first theory of their origins is the Multiregional Hypothesis, which holds that the ancestors of Homo sapiens were Homo erectus and intermediate species, and that modern humans all evolved in parallel from earlier populations in Africa, Asia and Europe. Most of the evidence for this hypothesis is anatomical.
The second theory is the Out of Africa Hypothesis, that holds that a small isolated group of early humans in Africa evolved into Homo sapiens and then migrated into Asia and Europe about 200,000 years ago, displacing, assimilating or annihilating all other early pre-human populations. Most of the evidence for this hypothesis comes from cell biology and DNA analysis.
HOMO SAPIENS NEANDERTALENSIS
The Neanderthals lived in Europe and western Asia, and are believed to have lived side by side with Homo Sapiens Sapiens. In some places they arrived after modern humans, which suggests that we are not descended from Neanderthals, but that we both descended from the same ancestors. They lived around 200,000 to about 30,000 years ago.
HOMO SAPIENS (MODERN)
All modern humans belong to the species Homo sapiens (modern), or Homo sapiens sapiens. The first of these were known as Cro-Magnons, and appeared at least 130,000 years ago. They used elaborate tools and left many cave paintings. Homo sapiens sapiens have generally lighter build than the earliest humans, but our brains are much larger.