The unfeeling reptilian brain: Don't mess with its babies
by Denyse O’Leary
(Note: I must write an index this weekend (for someone else’s book), and so I am posting some items I wrote for another blog that are relevant to the intelligent design controversy.)
Recently, while doing research for a book on human neuroscience issues, I ran into a really neat explanation of the brain, as follows:
Neurologist Paul MacLean first proposed in 1970 that the human brain has three parts, each one of which grew on top of the other, over evolutionary time:
- the reptilian brain (includes the brain stem and cerebellum)
- the limbic brain, associated with mammals, is responsible for emotions. It contains such structures as the amygdala and the hippocampus.
- the neocortex is best developed in primates and is associated with abstract thought, imagination, consciousness, and language.
This "three brains" hypothesis sounds neat — three nested brains — but it does leave the reptile without the ability to feel emotions other than aggression or perhaps fear.
Indeed, Maclean himself liked to say that "it is very difficult to imagine a lonelier and more emotionally empty being than a crocodile." For example, two behaviors that he did not think crocodilians could manage were care for offspring and playfulness.
Indeed, the vacant reptilian brain has even achieved a minor pop psychology status in business consulting as the last word in lack of creativity or caring.
One really good thing about the "three brains" hypothesis is that it can be tested. That's a key sign of a good hypothesis in science. Does the evidence reasonably show that crocodilians do not show emotions other than fear or aggression?
Doc Gater, who has wrestled and tagged hundreds of Mississippi alligators for conservation purposes, told me recently how he catches alligators in order to tag them:
Using a headlight on my head, I can see the eye shine of an alligator several hundred meters on a dark night. I then call the alligator for a closer look by mimicking the alarm call of a baby alligator and make splashing sounds with my hand in the water. The sound is irresistible and the alligator swims toward the boat. If I am working in a new area I can usually call about 80% of the alligators close enough for their heads to hit the boat.
When I call alligators by making the grunting call of a young alligator it attracts alligators of all sizes. It is unclear if they are simply curious or if they will defend the young. It is akin to the alarm call a newborn calf will make where the entire herd will indeed come and defend the young one.
So whether they are trying to be helpful or are merely curious, the alligators do not seem to realize that they are not supposed to care ...
Smith also told me, regarding the mother alligator's concern for her brood and the young alligators' awareness of each other:
Most mother alligators will viciously defend the nest containing incubating eggs and she has a very small home range (less than a third of an acre) during the 9-12 week incubation period. We know there is maternal care because the mother alligator MUST dig out the hatchlings and will often carry them to the water in her mouth. Also the grunting sound they make before hatching helps them all to hatch together and get the mother's attention. In fact if one puts less well developed eggs in a nest they too will hatch with the others, but with their yoke sacks still outside their bodies and will soon die. The young stay close to the mother and usually hibernate with the mother the first year or two. It remains unknown if the female alligator will actively defend the young after hatching, but her presence is certainly deterrence.
Alligators also seem to have something like a love life. According to gator expert Lindsey Hord, quoted in the southwest Florida News-Press, during mating season:
"You'll get higher visibility in males: Their mind is somewhere else, like teenage boys," Hord said. "They're showing themselves out. You'll see them in the middle of lakes and ponds with much of their body exposed. It's like saying to the females, 'This is my pond. This is how big I am.' "
And the 'gators seem to be attached to their home swamps as well. Smith notes,
Alligators also have an uncanny ability to return home after being moved. In Florida nuisance alligators are often relocated (as are bears in our parks), but were found to return in a few weeks. They finally concluded they MUST be relocated over 500 miles to avoid their return.
No one claims that alligators give to charity or solve equations, of course. But, based on evidence, it is reasonable to ask whether the reptilian brain is as lonely as proponents of the "three brains" hypothesis believe. And if the reptilian brain is not so lonely, is the "three brains" hypothesis really a satisfactory account of the evolution of the brain?
About the playfulness question, I haven't any information. If alligators are indeed playful, the over-curious human risks becoming a plaything. I have not heard of anyone so far who has volunteered for the basic research.