Why We Don’t Have a ‘Lizard Brain’

The notion that humans possess a 'reptilian brain' is a common misconception. For many years, this idea has permeated popular culture and scientific discourse, despite neurobiologists discrediting it. Today, we delve into the real story of human brain evolution and debunk some of these myths.

Revolving Around the Myth of the 'Lizard Brain'

One of the most pervasive phrases in discussions about the human brain is the term 'lizard brain.' This term generally refers to the brain stem and associated structures, which are shared with reptiles and are crucial for consciousness and homeostasis. However, the assertion that humans possess a 'lizard brain' is fundamentally flawed.

Neurobiologists Cesario J. Johnson, DJ, and Eisthen HL, in their article 'Your Brain Is Not an Onion With a Tiny Reptile Inside' published in Current Directions in Psychological Science, argue that the 'lizard brain' terminology has been long discredited. They emphasize that nervous-system evolution is a respected field with a clear and unanimous consensus among its scholars.

This 'lizard brain' moniker is not only misleading but also disrespectful to lizards, which can be quite intelligent. Lizards do have brains that enable basic consciousness and awareness, just like other animals, including humans. The brain stem, with its structures like the reticular formation (or reticular activating system), plays a crucial role in consciousness, which is essential for all animals, including primates.

The True Foundations of Human Brain Evolution

The human brain is a testament to evolutionary progress. It consists of several layers of functionality. The core, innermost portion of our brain, shares similarities with that of reptiles, controlling basic homeostasis and instinctive drives. However, this does not make us inherently 'reptilian.'

Our neocortex, the outermost layer of the brain, is notably larger than that of our primate relatives, such as chimpanzees, due to the presence of the FOXP2 gene. This gene contributes to the development of a significantly larger prefrontal cortex, which is integral to higher cognitive functions, reasoning, and decision-making.

Many regions of the human brain, like those governing basic homeostasis and instinctive drives, are indeed similar to those in reptiles. This is unsurprising, given that the human brain evolved iteratively from earlier brain structures. However, the term 'reptilian brain' is a misnomer. It erroneously suggests that the human anatomy descended from lizards or any other reptiles.

The term 'reptilian brain' refers to the basic plan inherited from the common ancestor of humans and reptiles. It is also important to consider hundreds of modifications that have occurred over millions of years of evolution.

The Diverse Layers of the Human Brain

The human brain is a remarkable structure consisting of three main components:

Brain Stem: This area controls basic functions such as breathing, heartbeat, and consciousness. It is highly similar to the one found in reptiles and is essential for our survival. Cerebral Cortex: The outer layer, particularly the neocortex, is responsible for higher cognitive functions, including reasoning, problem-solving, and complex behavior. It is significantly larger in humans compared to other primates. Cerebellum: This area is involved in movement coordination, balance, and procedural learning. While not as 'primitive' as the brain stem, it still contains structures that are modified versions of those found in reptiles.

The complex layers of the human brain, each with its unique functions, demonstrate a profound evolutionary journey from ancestral reptiles to modern Homo sapiens. Understanding the progression of brain evolution is crucial for comprehending our cognitive capabilities and the unique traits that set us apart from other species.

Conclusion

In conclusion, while our brain shares some structural similarities with that of reptiles, this does not mean humans have a 'lizard brain.' The term 'reptilian brain' is outdated and misleading. The human brain is a marvel of evolutionary history, with each layer of the brain contributing uniquely to the complexity of human cognition and behavior.