Evolution of the Homo Genus

EVOLUTION OF THE HOMO GENUS

As mentioned, the earliest human and the first to have used tools was Homo habilis, who was the prototypical caveman”, using stone tools. The Homo habilis brain wasn t very big but it was believed to have been wired more efficiently. Encephalization occurred soon after this, which resulted in Homo erectus and Homo ergaster. In fact, the cranial capacity doubled in size at the time of their arrival. These early humans were likely the first to make use of fire and more complex tools. These were the first also to leave Africa to all parts in the Northern Hemisphere in Eurasia.

Modern humans probably evolved from Homo rhodesiensis, Homo heidelbergensis, or Homo antecessor, migrating out of Africa the last time about 55,000 years ago, although some believe it could have been as early as 100,000 years ago. These replaced the local populations in Eurasia of the Denisovans, Neanderthals, Homo floresiensis, and Homo luzonensis. Archaic Homo sapiens were the original prototype of modern man.

At some point, there was the evolution to more modern cultures, language, and complex stone tools, which may have occurred about 50,000 years ago, although there is disagreement as to whether this happened all at once or gradually over time. Eventually, all of the Homo genuses died out and became extinct except for Homo sapiens.

We cannot underestimate the impact of the environment on human evolution. There was, for example, the super-eruption of Lake Toba in Indonesia about 70,000 years ago that had global implications on evolution. It is believed that most humans were killed and the population dwindled before taking off again over time. This phenomenon is referred to as a population bottleneck.

Homo habilis directly diverged from Australopithecus in South and East Africa about 2.5 million years ago. Stone and animal bones were used as tools by this primitive form of man. There are some who believe this species should be moved back to the Australopithecus genus because they were adapted to living in trees and did not move easily as bipedal primates.

Homo erectus was first identified in Indonesia. It was originally called a form of Anthropopithecus rather than one of the Homo genera. The skeleton, called Java man, was compared to Peking man at a later date and it was determined that both were the same and they were renamed to become Homo erectus. They were likely wiped out by the Toba catastrophe because of their proximity to Indonesia during the super-eruption. Homo ergaster is either a separate species or a subspecies of Homo erectus.

With the increase in brain size in Homo erectus, there was also a decrease in intestinal capacity and a lesser efficiency of the brain in terms of nutrient use. This is what may have led to cooking food so it could be more nutritious for the body and brain. Peking Man in Asia is an example of Homo erectus.

Intermediate species include Homo cepranensis, found in Italy, Homo antecessor, found in Spain and England, and Homo heidelbergensis or Heidelberg Man. Homo rhodesiensis or Rhodesian man is believed to be related to or the same as Homo heidelbergensis.

We know more about Neanderthals and Denisovan man, who were more recent. Neanderthals lived in Europe and Asia around 28,000 to 400,000 years ago. The Neanderthals were particularly adapted to cold environments; they are believed to be similar to what s seen in the Inuit population and they had larger brains. Researchers believe that Neanderthals lost less body heat and could see better than modern humans. They needed a larger brain to control their larger bodies and may have been physically better than humans. They had fewer social skills and lesser use of tools compared to anatomically modern humans. There were more humans in terms of numbers so the Neanderthals were replaced. Modern man coexisted with Neanderthals for 10,000 years in Europe.

The Denisovans were first found in Siberia. DNA was able to be sequenced and carbon dating showed they lived around 40,000 years ago. They come from the same lineage as the Neanderthals and may also have coexisted with anatomically modern humans. As mentioned, there is evidence of interbreeding with humans in Southeast Asia. Denisovans and Neanderthals are more closely related to one another than they are to humans.

Homo floresiensis is an interesting species that existed about 190,000 to 50,000 years ago. These are sometimes called hobbits because of their small size. They carry a common ancestor to modern humans but followed their own evolutionary pathway. They were about one meter in height and had small brain capacities. Some believe that what was found to support this as a separate species was not enough to call them a separate species but instead represented a human with pathological dwarfism. The remains were found on the Flores Island in Indonesia, where pygmies can be found. The skeleton was found with human tools. Because others were found to look the same, there is also support for the separate species” idea.

The term, Homo sapiens, means wise one” or intelligent one”. Most believe the species was derived from Homo heidelbergensis although interbreeding of more than one species could also have happened. The Toba Catastrophe led to a population bottleneck and likely played a role in the genetics of modern man since that time.