How did the earth as we know it come to be? In Geography class 11: Theories of Evolution, we will discuss different theories and hypotheses about the origin of the earth and universe by philosophers and scientists. 

Early theories of Evolution 

Origin of the earth 

Nebular Hypothesis

• German philosopher Immanuel Kant put forth the nebular hypothesis in his book the “Universal Natural History & Theory of the Heavens” in 1755

• Mathematician Pierre-Simon Laplace re-examined the hypothesis in 1796

• The hypothesis suggested that planets were moulded from clouds of gaseous materials associated with the young sun. 

Revised Nebular Hypothesis

• In 1950, Carl Weizascar of Germany and Otto Schmidt of Russia revised the hypothesis

• According to the revised nebular hypothesis, the sun is surrounded by a solar nebula made of hydrogen, helium, and dust

• As per the revised nebular hypothesis, planets were formed through the process of accretion. 

Binary Theories

• The binary theory refers to the theories that scientists and philosophers considered a companion to the sun, which would have been coexisting

Modern theories of Evolution 

Origin of the Universe

After developing different theories on the origin of the earth, scientists and philosophers focused on the origin of the universe and developed several theories. 

Big Bang Theory

• The Big Bang Theory is also called the expanding universe hypothesis

• In 1920, scientist Edwin Hubble developed Hubble’s law, also known as the Hubble-Lemaitre law. Edwin Hubble observed that galaxies are gradually moving away from earth at a speed that is proportional to their distance

• The Big Bang Theory says that all the matter which made the universe, existed as a tiny ball at the beginning of the universe

• According to this theory, when the big bang occurred approximately 13.7 billion years ago, the tiny ball from which the universe originated burst fiercely and started expanding.  

Development of the universe as per The Big Bang Theory

• The universe’s development as per the Big Bang Theory is divided into 2 stages-in the beginning, and at the big bang

• This theory suggests that in the beginning, all matter existed in one place as a tiny ball

• This tiny ball had a small volume, infinite temperature, and infinite density

• At the big bang, the tiny ball exploded violently and began its expansion process. A process that continues to this day

• It is assumed that there was rapid expansion after the explosion and that expansion has since slowed down. 

Hoyle’s concept of steady-state

• Hoyle’s concept of steady-state is an alternative to the theory of an ever-expanding universe

• Hoyle’s concept of steady-state considers the universe to be of the same size all the time

• However, evidence has been collected that supports the theory of an expanding universe, which makes this concept unfavourable within the scientific community

Evolutionary theories focus on the origins of the human species across time. According to this viewpoint, modern people contain genetically directed features that have been handed down from generation to generation and have helped to survival and reproductive success. This chapter discusses the role of adolescence in Darwin’s concept of fitness, the relationship between human adolescence and adolescent development in other primates, and the concept of adaptation to an ecological niche. The chapter uses evolutionary psychology principles to analyse the integration of genetic and social influences that result in phenotypes linked to puberty, group faithfulness, sex-specific sexual techniques, aggression and bullying, and the adaptive character of hazardous behaviours.

Things to Keep in Mind About Evolution

• Evolution is not progressive – Evolution is not intended to develop the highest quality goods; rather, it strives to build adaptations “that will perform the job” most effectively and inexpensively. As a result, evolution employed the mammal template’ throughout the development of all mammal species – for example, pentadactyl limbs, mammary glands, spine curvature, and pelvic anatomy – and made the required adaptations to fit the niche the species lived in
• Evolution is not a justification for the status quo; it does not explain why things are the way they are. It is important to note that certain animal characteristics may be trade-offs or by-products of the development of an unrelated adaptation
• Evolution imposes restrictions – What has come before places physical constraints on what we may achieve today. This may be demonstrated in the fact that we learn certain things considerably faster than others. In this way, evolution has also limited what we can notice and attention to
• Evolution creates complexity from simple – Species that rely on one other for food (predator-prey interactions) often engage in ‘arms races’ to outdo each other

Conclusion

Natural selection develops adaptations and determines individual reproductive success. Adaptations are anatomical features, physiological processes, or behavioural patterns that aid in ancestral survival due to the specific appropriateness of certain traits / qualities (Crawford, 1998). Natural selection is the difference in reproductive success. Natural selection happens as a result of an interaction between the environment and the intrinsic variety among the individual organisms that comprise a population. Natural selection in the adaptation of organism populations to their surroundings.