The genus homo, or human, has existed for more than 2 million years. Our species, Homo sapiens, is only the most recent example. Anthropologists aren't certain how many human species have existed because new discoveries occur frequently. For example, Australian and Indonesian scientists discovered a new species, Homo floresiensis, in 2004.
Homo habilis, or handy man, existed 2.4 to 1.4 million years ago. They had larger brain cases and smaller teeth and faces than earlier hominids but retained some ape-like features such as long arms. They were named handy man because anthropologists once believed they were the first species to make stone tools. However, the earliest stone tools are older than the genus homo.
Homo erectus, or upright man, lived between 1.8 million and 500,000 years ago. They were the earliest known humans with proportions similar to our own. They had short arms and long legs for living on the ground rather than in trees. Anthropologists studied Homo erectus' teeth and discovered that Homo erectus grew at the same rate as a great ape. They used fire and made more sophisticated tools than Homo habilis.
Some anthropoligists consider specimens of homo erectus members of a separate species, Homo ergaster. Homo ergaster lived about 1.7 to 1.5 million years ago. Homo ergaster remains are distinguished from Homo erectus by differences in the shape of the skull such as lighter features, different shaped brow ridges and a higher brain cavity or cranial vault.
Homo antecessor, or pioneer man, lived in Europe at least 780,000 years ago, the earliest known Europeans. Homo antecessor had a modern-looking face but primitive teeth, brow ridges and foreheads. Anthropologist Jose Bermudez de Castro believes that Homo antecessor was the direct ancestor of both Neanderthals and modern humans. However, most anthropologists believe that modern humans and Neanderthals are descendants of either Homo erectus or Homo ergaster.
Homo heidelbergensis lived 700,000 to 200,000 years ago. They possessed larger brain cases and flatter faces that earlier human species. They were also the first human species to live in colder climates. Anthropologists believe that their short, wide builds help them conserve body heat. They are also the first known species to build simple shelters out wood and rock.
Homo neanderthalensis, or neanderthal man, lived between 200,000 and 28,000 years ago. They had large faces, angular cheekbones and large noses. Large noses helped humidify and warm the ice age's cold, dry air. They had short, stocky bodies designed for dealing with a cold climate but their brains were as big as ours. Neanderthals buried their dead, used fire, built shelters and used sophisticated tools.
The fossils of Homo floresiensis were discovered on the Indonesian island of Flores in 2003. Homo floresiensis lived between 95,000 and 13,000 years ago. They had an extremely small stature and stood about 3 feet tall. They've been nicknamed hobbits after the diminutive race in J.R.R. Tolkien's "The Lord of the Rings." Homo floresiensis used stone tools and hunted pygmy elephants, Komodo dragons and giant rats.