BY DR. JOSE PALU-AY DACUDAO
GONE ARE the days when dinosaurs are depicted as slow-moving cold-blooded stupid pea-brained creatures, dragging their tails on the ground as they sluggishly go about with the business of life.
Although paleontologists already knew that, it was probably the 1993 film Jurassic Park directed by Spielberg and based on the book by Crichton that demolished this view in the eyes of the public.
It must be said that as a fan of Bakker’s theory, I wasn’t surprised that the film depicted dinosaurs as warm-blooded, quick, and moved their heads and S-shaped necks with a bobbing motion and leaving footprints exactly like that of modern birds.
A host of fossil findings also indicate that dinosaurs grinded their food with small stones inside gizzards, lived in herds or packs, brooded their eggs (again like your modern chicken and sparrow).
As for their so-called tiny brains and alleged stupidity, Jerison, in the 1970s, showed that as the body increases in size, the brain becomes smaller in proportion; and thus, dinosaurs’ brains are comparable to that of extant reptiles.
Moreover, as time passed, the relative size of the brain also increased among theropods, and is largest among maniraptoran theropods, the clade to which birds belong to. In other words, these ancient maniraptoran dinosaurs had relative brain sizes that match that of modern birds, and they are believed to be just as intelligent.
You might ask why did dinosaurs never evolve to be as intelligent as mammals?
In my opinion it is because dinosaurs do not possess a cerebral cortex. Both reptiles and mammals possess deep gray matter composed of neuronal cell bodies. (A neuron is made up of a neuronal cell body and processes that project from it – axon and dendrites.)
But mammals also possess neurons that cover the brain, called the neo-cortex or neo-pallium. The brains of mammalian fetuses start out with the same set of deeply located neurons as reptiles.
However, in mammalian ontogeny, some of the stem cells of the neurons from the deep gray matter located around our ventricular system migrate to the outside to cover the cerebral hemispheres. They multiply and become the cerebral neo-cortex (also called neo-pallium), or in layperson’s terminology, new-covering.
So, mammals have evolved a second set of neurons, or from a layperson’s perspective a second set of brains.
In brief, we possess both a ‘reptilian brain’ (as popular press calls the neuronal nuclei of the deep gray matter) and a neo-cortex. Thus, we have a whole lot more neurons than reptiles. Two ‘brains’ are better than one. (To be continued)/PN
