Homo

Homo (from Latin homō 'human') is a genus of great ape (family Hominidae) that came from the early hominin genus Australopithecus. Today, it includes one living species, Homo sapiens, which are modern humans, along with several extinct species like Homo erectus and Homo neanderthalensis, known as archaic humans. These ancient humans were closely related to us and lived millions of years ago.

The oldest known member of the Homo genus is Homo habilis, whose fossils are over 2 million years old. Homo erectus appeared around the same time and spread across Africa and Eurasia in several migrations. They were very adaptable and survived for more than a million years.

Anatomically modern humans, early H. sapiens, appeared in Africa between 300,000 to 200,000 years ago. Around the same time, Homo neanderthalensis emerged in Europe and Western Asia. H. sapiens left Africa in several waves, starting possibly as early as 250,000 years ago, and certainly by 130,000 years ago. By 50,000 years ago, they had colonised Eurasia and Oceania. Modern humans met and interbred with archaic humans during these journeys.

Names and taxonomy

Main articles: Human taxonomy, Names for the human species, and Homininae

The word "Homo" comes from Latin and means "human being" or "man." The scientific name for modern humans, Homo sapiens, was given by Carl Linnaeus in 1758. Other human-like species were named later, such as Homo neanderthalensis in 1864 and Homo erectus in 1892.

The group Homo has not always had clear rules for which species belong to it. When scientists first named Homo, they only thought of modern humans. But when they discovered Neanderthals, they added another species. Over time, many fossils were found, and scientists debated which ones belonged to Homo. What ties them together is that they could walk on two legs like us and made tools.

Many old names for early human-like species have now been grouped under Homo. For example, names like Pithecanthropus and Sinanthropus are now considered part of Homo erectus. Scientists still argue about how to sort these species, especially when new fossils are found. Today, it seems that only Homo sapiens modern humans have been alive since the end of the last ice age.

Evolution

Main article: Human evolution

Further information: Timeline of human evolution, Hominini, and Chimpanzee–human last common ancestor

Australopithecus and the appearance of Homo

Further information: Australopithecus

Some early species, like Australopithecus garhi, Australopithecus sediba, Australopithecus africanus, and Australopithecus afarensis, might be related to the start of the Homo group. These species share some features with Homo, but scientists are not sure which one was the true ancestor.

Since the 2010s, it has become harder to know exactly when Homo began. Traditionally, it was thought to start when early humans first used stone tools. But in 2010, scientists found evidence that Australopithecus afarensis might have used stone tools around 3.3 million years ago, much earlier than Homo appeared. A fossil found in 2013 in Afar, Ethiopia, called LD 350-1, shows a mix of older and newer features. Some scientists now think Homo might have started as early as 3.3 million years ago, while others believe it was later, around 1.9 million years ago.

One big change from earlier species to Homo is the increase in brain size, from about 460 cm³ in A. garhi to 660 cm³ in H. habilis, and even larger in later species.

Homo habilis

Homo habilis appeared about 2.1 million years ago. Before 2010, some scientists thought H. habilis should not be part of Homo, but in Australopithecus. One reason to put it in Homo was that it used tools, but we now know that some Australopithecus species used tools even earlier. Also, H. habilis and H. erectus lived at the same time, meaning H. erectus might not have come directly from H. habilis. Instead, they might have shared a common ancestor.

Homo erectus

Homo erectus is often thought to have developed from H. habilis about 2 million years ago. Fossils found in the Caucasus showed traits between H. habilis and H. erectus, like a bigger brain size, growing from about 575 cm³ in H. habilis to around 850 cm³ in H. erectus. Early H. erectus fossils were found outside Africa, making some think H. erectus developed in Eurasia and later moved back to Africa. Studies also suggest that H. habilis might have lived at the same time as H. erectus for about half a million years.

Phylogeny

The group Homo belongs to the family of great apes. It includes modern humans, known as Homo sapiens, and several extinct species like Homo erectus and Homo neanderthalensis. These older species are closely related to us and are often called archaic humans.

Homo and another group called Paranthropus are thought to share a common ancestor with a species named Australopithecus africanus. Scientists are still learning about the exact family tree and when these groups split apart. Some ancient Homo species, such as Homo erectus, may have mixed with other early human groups, leaving traces of their DNA in modern humans today.

List of lineages

See also: List of human evolution fossils

The exact classification of some early human-like species, such as H. rudolfensis, H. ergaster, H. georgicus, H. antecessor, H. cepranensis, H. rhodesiensis, H. neanderthalensis, Denisova hominin, and H. floresiensis, is still being studied and debated by scientists.

Some scientists suggest that there were only three main species of early humans: H. habilis, H. erectus, and Homo sapiens. However, scientists do not always agree on how to define a species, making this a complex topic. It's important to note that these early human species could sometimes interbreed with each other, even after they had started to evolve separately.