Evolution of the genus Homo. Charles Darwin was the first to formulate a scientific argument for the theory of evolution by Natural Selection. The idea of natural selection is basically “the survival of the fittest. ” Evolution is any change in characteristics in biological populations. It gives diversity to life on all known biological organizations such as molecules, organs, organisms, etc. Life is said to be originated from a universal common ancestor, which tells us that all life is related to each other.
Life started from simple celled organisms known as prokaryotes, which evolved into eukaryotes after photosynthesizing bacteria evolved forcing oxygen concentration to rise in the atmospheric. This event known as the Great Oxidation Event acted as poison on many bacteria that use carbon dioxide as an energy source. After the evolution of eukaryotes, sexual reproduction appeared and increased the evolution rate tremendously. Complex multi-cellular organisms started to appear soon after, first in oceans and then on land.
Over time, life diversified into millions of organisms. The genus Homo first evolved around 2. 5 Ma from Australopithecine genus (now extinct). The first homo species believed to evolve were called Homo Habilis. They lived side by side with another homo species called Homo erectus until at least 1. 44 Ma. H. Habilis were also the first species to make tools out of stone. H. Erectus resembled modern humans and colonized in Africa. They had a brain size 74% that of modern humans and had ways of making better tools and also hunted bigger animals.
Another species, Homo Antecessors were common ancestors of humans and H. Neanderthals. Modern humans shared 99% of their DNA with Neanderthals and Neanderthals also had a similar gene linked to speech. Another species, Homo Heidelbergensis may be an ancestor of Neanderthals and modern humans. Finally, modern humans or Homo Sapiens are said to first appeared around 200 Ka around Oma river, Ethiopia. There are two famous models that explain where the modern day humans originated from. Both models are supported by evidence and therefore are accept by different scientists.
The Replacement model says that modern humans originated in Africa and replaced all other archaic humans beginning 60,000 years ago. The regional continuity model argues that all modern human evolved more or less simultaneously in all major parts of old world from local archaic humans. It is believed that environmental variables, along with natural adaption, such as pathogens, diet, survival needs, climate, etc. caused the different phenotypic diversity among human populations thus complicating the puzzle of modern human evolution.