Brain size is believed to have tripled over the period of human evolution. Today, the human brain is known to be one of the largest and the most complex that has developed since early humans days. Brain size is said to have evolved concurrently with the increase in brain to body ratio. As mentioned under the cultural evolution tab, early humans had developed stone tools and such technological advancements together with new environmental challenges that primates faced in the past, tested humans’ fitness for survival. This led to the development of bigger bodies and thus bigger brain size and much more complex brains. As a result, presently, our brains are able to process and store more information due to its larger capacity, serving us a big advantage.
Figure 2 below illustrates how brain capacity or volume has increased over time with comparison to the climate fluctuation patterns. As seen within the red zone, during the period of great climate fluctuation, it has led to the greatest volume of brain size increase. Henceforth, this may provide the explanation as to how and when the human brain evolved significantly to how it is today (Brains, n.d.).
In addition, the development in brain capacity is further supported by the theory that primary tool making techniques and process of early humans has acted as a stimulus in the specific brain region specialised for manual manipulations and speech production. This improvement in technological aspect of early humans emerged during the period of the Homo Habilis. Over time, this resulted in a gradual increase in brain size as shown in the diagram below (Bolhuis et. al, 2014).
From 6 – 2 million years ago
Slight increase in Brain Size
Bipedalism, which is the way of walking upright started in early humans. It then resulted in the advancement of simple tool making. Thus, brain size increased slightly.
From 2 million – 800,000 years ago
Increase in Brain to Body ratio
This was the period where early humans began dispersing across continents. This led to the various encounters of new environments. With the process of natural selection, due to the challenges faced, the early humans experienced an increase in body size, which simultaneously resulted in bigger brains.
From 800,000 – 200,00 years ago
Rapid increase in Brain Size
The bio-climatic effects that occurred during this period has caused the human brains to evolve most significantly (Beals et. al, 1984). These environmental forces influenced the way early humans interact with their peers and surroundings thus resulted in a larger and more complex brains in order to cater to the needs of early humans. This proves to be an essential mean of survival which enabled our ancestors to last till today (Brain, n.d.).