Homo
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Species of genus Homo
Homo habilis
Homo habilis (handy-man) was a species of Homo living 2.5 to 1.5 millions years ago. Tool usage is said to have first emerged in a complex form in this species. Physically, they had more human like dentition and facial structure than australopithecines, but their braincases were no larger. However, they had a small stature and had even more ape-like limb proportions than the gracile australopithecines, such as Lucy, and so some anthropologists doubt the status of this species within the Homo genus.
Homo ergaster
Homo ergaster or working man is probably the first "true" human, despite earlier examples of Homo existing. Homo ergaster lived around 1.6 million years ago, making him a contemporary of Homo erectus. Some anthropologists consider ergaster and erectus to be different variants of the same species while others consider ergaster to be our ancestor while erectus was an evolutionary dead-end. They had a cranial capacity roughly two thirds that of modern man, much larger than Homo habilus but still considerably smaller than sapiens. It is thought that ergaster mastered the use of fire and cooked its food. They also have a more advanced tool kit that previous hominids.
Homo erectus
Homo erectus which is sometimes considered the same species as Homo ergaster was a early to mid Pleistocene hominid that lived between 2 million years ago and 750,000 years ago. He had a brain capcity of 850 to 1100 cc compared to 1350 for a modern human indicating some change over the 1.25 million years it existed. Homo erectus along with Homo ergaster and Homo heidlebergensis may be part of a chronospecies along with Homo sapiens. Other scientists disagree and believe that Homo erectus represents an evolutionary dead-end of a lineage of Homo. Homo erectus does have more modern features when compared to earlier hominids and this indicates a closer relationship with modern humans and indicates that erectus or a closely related species was our direct ancestors. In addition it has been suggested that Homo erectus may have been the first hominid to use rafts to travel over oceans but however this idea is controversial within the scientific community.
Homo heidelbergensis
This mid-Pleistocene human lived between 800,000 and 600,000 years ago. He resembled a modern human but was more robust and slightly taller, averaging about 6 feet in height for adult males. He had features intermediate between Homo erectus and Homo sapiens. Homo heidelbergensis has been referred to as both late Homo erectus and archaic Homo sapiens. It is speculated that Homo antessor which there is only one fossil of, may be the same species as Homo heidelbergensis. This would make Homo heidelbergensis the last common ancestor of modern man and Neanderthals[1].
Homo neanderthalensis
Neanderthals were a late Pleistocene human that was a contemporary with modern humans. It lived from 130,000 to 24,000 years ago throughout Europe. They resembled modern humans but had a pronounced brow ridge and were shorter but much more robust. Neanderthals died off 24,000 years ago, about 16,000 years after the arrival of modern humans in Europe. It is speculated that modern humans may have contributed to the demise of the Neanderthals but that does not explain why both species co-existed for 16,000 years. Others speculate that there was no genocide and that Neanderthals were not as technologically adapted as modern humans, while others speculate that the two closely related species merged into one.
Homo floresiensis
Homo floresiensis was a dwarf species of human that lived with pygmy elephants (of the genus Stegodon) and giant predatory monitor lizards, possibly related to Komodo dragons, on the island of Flores in Indonesia between 95,000 and 13,000 years ago. They had a braincase only about the size of a chimpanzee and were only as big as a three year old child but had all the behaviours of humans. They were also the only human species besides the neanderthals who were contemporaries of modern humans. It is believed that Homo floresiensis evolved from an isolated population of Homo erectus who arrived on the island around 840,000 years ago and selection pressures caused them to become smaller over time but however some scientists have suggested that the Homo floresiensis fossils found on the island of Flores were not members of a different species known as Homo floresiensis but were instead modern humans that were affected by a condition known as microcephaly ,which produces an unusually small brain and skull. Despite their small brains, their use of fire, advanced stone tools such as spears, and hunting of relatively large game indicates that they were likely as intelligent as their contemporaries and certainly much smarter than a chimp. When the first floresiensis skeletons were unearthed, scientists at first thought they were a diminutive human but are now confident floresiensis represents a distinct species. It is also thought that modern humans have encountered floresiensis. It is unknown what transpired when the two species met. Homo floresiensis dies out near the end of the Pleistocene around 13,000 years ago or around 11,000 BC [2]. It is believed that they had some contact with H. sapiens, as legends of a dwarfish race, called "Ebu Gogo," (literally "Grandma Glutton") persist in the local folktales.
Homo sapiens
The species to which we belong. We evolved sometime in the late Pleistocene in Africa around 200,000 years ago. It is believed that Homo sapiens evolved from more Archaic forms including Homo heidlebergensis which lived around 600,000 years ago and Homo rhodensis (sometimes called Homo sapiens rhodensis) which lived around 300,000 years ago). Some scientists considered Homo heidlebergensis and Homo rhodensis archaic Homo sapiens and included Neanderthals in our species. Now the Neanderthals are considered their own species and Homo heidlebergensis is also considered its own species. The taxonomic status of Homo rhodensis is undecided but scientists believe that rhodensis is a direct ancestor to early modern humans (Homo sapiens idaultu or elderly wise man). The first "true" Homo sapiens (subspecies idaltu) are known to have existed around 160,000 years ago but may have existed for more than 200,000 years. The subspecies to which we belong appeared in Africa around 130,000 years ago and radiated across the world, reaching all corners of the globe (except Antarctica) around 12,000 years ago. There were two models of the origin of Homo sapiens; the multiregional hypothesis which has now been refuted and the "Out of Africa" hypothesis which evidence suggests is correct. The multiregional hypothesis statest that our species evolved from a network of interbreeding Homo populations scattered throughout the Old World while the "Out of Africa" model suggets a recent origin of modern man (around 100,000-150,000 years ago) replacing all other human species throughout the world. The second hypothesis has more evidence although there is evidence to suggest at least some modern human-Neanderthal hybridization has taken place. How much DNA Neanderthals contributed to modern man is not known [3].
