Dawn of Humans

The genus of humans is known as 'Homo.' Homo is a member of the family of 'great apes.' Modern human beings, also known as Homo sapiens, are closely related to the great apes' primate group of species, including the chimpanzee and the gorillas. Genetic analysis suggests that these primates had the latest common ancestors (LCA) 9 to 6 million years ago. Evidence shows that humans share about 98.7 percent of their DNA with chimpanzees. Therefore, a chimpanzee is considered a more recent common ancestor than a gorilla. Several Homo species have been discovered that contributed to the evolution of modern Homo sapiens. A timeline for the evolution of humans on Earth is shown in Figure 2.10.

Several Homo species that evolved over time were distinct compared to other animals. For example, one of the distinguishable features of humans is the ability to walk on two legs. It is a unique trait named bipedalism. Early fossils and archeological remains indicate that bipedalism evolved about 6 to 4 million years ago (mya). Furthermore, several fossils belonging to the period from 6 mya to 2 mya have been found only in Africa; therefore, it is assumed that human evolution started in Africa.

Several other members of the genus Homo, such as Homo habilis and Homo erectus, are known to have evolved. It is estimated that they have survived for about 2 million years. Neanderthals, another member of the genus Homo, evolved in Europe and West Asia about 400,000 years ago. A comprehensive dating of the Neanderthal bones and tools from hundreds of European sites indicates that European Neanderthals died out between 41,000 and 39,000 years ago. However, the Neanderthals contributed to the DNA of modern humans between 60,000 and 50,000 years ago through interbreeding.

In 2010, scientists discovered fossilized bones belonging to a human species named Homo Denisova found in Denisovan caves in Siberia. Furthermore, recent DNA mapping studies have found that the human population of Europe and the Middle East has between one to four percent of the unique human DNA of the Neanderthal DNA. Also, in Australia, Melanesians and Aboriginal Australians have 6% of the unique human DNA of the Denisovan DNA. Therefore, we conclude that modern human beings have evolved mainly from the Homo sapiens and, to a small extent, from the Neanderthals and the Denisovans.

Early humans started migrating out of the southern part of Africa. They migrated to other continents in one or perhaps two major migration waves. The first migration happened in Asia about 2 million years ago. Migration to Europe occurred between 1.5 million to 1 million years ago. The spreading of modern humans into other parts of the world happened much later. Modern humans migrated to Siberia and Australia about 60000 to 35000 years ago. They arrived in America between 30000 to 15000 years ago. Archeological data based on carbon dating, linguistic study, and genetic data based on the molecular clock are used to estimate the spread of humans in various regions worldwide. The studies indicate that it is the Homo sapiens who have displaced all other human species and survived.

We have presented the timeline for the beginning of life. It took more than 9 billion years since the beginning of the universe for the Sun and Earth to be born. It is shown that the early signs of life are more than 4 billion years old, as determined from the analysis of the fossils that lay preserved in the rocks. The techniques for the fossil analysis using radiocarbon dating can be relied upon, providing results with known accuracy. These techniques suggest that all life forms evolved from a common ancestor as the genes comprising the last universal common ancestor are identified. The well-known theory of evolution spelled the emergence of species of higher intelligence from simpler life entities. Early signs of humans that appeared in the last few million years evolved into several Homo species, although Homo sapiens one is the only surviving today.