The idea of the lizard brain first emerged and rose to popularity in the 1960s and 1970s, based on comparative anatomical studies. Parts of the mammalian brain, neuroscientist Paul MacLean noticed, were very similar to parts of the reptilian brain. This led him to the conclusion that the brain had evolved in stages, after life moved to land.

First, according to MacLean’s model, came the reptilian brain, defined as the basal ganglia. Then came the limbic system – the hippocampus, the amygdala, and the hypothalamus. Finally, the neocortex arose in primates.

Under the triune brain model, each of these sections is responsible for different functions; the more basal parts of the brain, for example, were supposedly more concerned with primal responses – like basic instincts for survival.

However, neuroscientists have been decrying the model for decades. The brain just doesn’t work like that, in discrete sections that each play a separate part. Brain regions, anatomically distinct as they are, are highly interconnected, a web of humming neural networks. And with the advent of new techniques, we can start to better understand how brains evolved.

In a new study, a team of researchers from the Max Planck Institute for Brain Research turned to actual lizard brains to investigate, publishing their findings in a paper led by neuroscience graduate students David Hain and Tatiana Gallego-Flores.

[article written in 2022]