Chemical evolution refers to the processes that created the biomolecules, and then formed structures called protocells. According to Oparin, the first biomolecules were synthesized when the components of Earth’s primitive atmosphere reacted on contact with each other.
Biological evolution refers to the processes that led protocells to become different types of cells, and resulted in all the different organisms ever to have inhabited the Earth. Different types of prokaryotic cells were created from primitive cells: heterotrophic cells, photosynthetic cells, aerobic cells, long and very mobile cells.
Fixist theories uphold the idea that the species that currently exist on Earth were created by God in the form that we see them today, and that they have not changed in any way throughout the history of the Earth.
Theory of Catastrophism
According to the theory of catastrophism, Earth had experienced many catastrophes in its history and these had led to the disappearance of many species.
An internal impulse exists within organisms that drives them to improve themselves and become more complex. Environmental changes have an impact on this process, causing the organisms to use some organs more than others, and resulting in the organs either becoming more developed or atrophying. The characteristics acquired through their use or disuse are transferred to the next generation.
When the resources are limited, the organisms in that population enter in a struggle for survival. The only individuals that survive are those that have variations which make them fitter. The fittest individuals leave more descendants and transfer the favorable characteristics that helped them be successful to their offspring. The less well-suited, with some disadvantageous traits, which means these characteristics begin to disappear from the population.
Main Characteristics of Hominids
- They are bipedal. This leaves their hands free to carry and use objects.
- They have small teeth, which are not used for defense or attack.
- They have a large brain.
It was the first of our relatives to have human-like body proportions, with shorter arms and longer legs relative to its torso. It was also the first known hominin to migrate out of Africa.
The first known species of Homo appeared in East Africa. Stone tools were found with these fossils, that is why this early human species was named Homo habilis.
Together with an Asian people known as Denisovans, Neanderthals are our closest ancient human relatives.