So wrote Carl Sagan in his best-selling book “Cosmos,” published in 1980.

I always found the notion that human beings possess a rudimentary reptilian brain to be very believable. It explains a lot. Another thing I’ve noticed is that the older I get, the more I hang onto strongly held beliefs that have been debunked by modern science or contemporary sentiment. I think this is generally true among members of the Baby Boom generation.

By the way, whatever happened to the Age of Aquarius? You never hear about it anymore.

Baby Boomers indeed. The very title is ludicrous these days, applying as it does to a bunch of oldsters. The Mamas and the Papas now would be referred to as the Nanas and the Poppas. I remember the song “The Boy from New York City” by the Ad libs, released in 1965:

“Ooh wah, ooh wah, cool cool Kitty, tell us about the boy from New York City….And he’s cute, in his mohair suit…”

I’ll tell you about the boy from New York City. He used to be cute, but now he’s a coot. Known as “the dazed and confused generation,” Baby Boomers are no longer babies.

Back to the reptile brain — we all have one! It’s a splendid way to explain away, if only to ourselves, those occasional instinctive and impulsive outbursts of anger, aggression, jealousy and covetousness that seem to come from nowhere. They are merely the promptings of our inner snapping turtle, rising up through the murky waters of the subconscious mind. Heaven knows, we are actually very civilized. Were it not for that atavistic reptile brain and its primeval instincts we would never have acted that way!

Perhaps criminals are guided, for one reason or another, by the promptings of their reptile brains rather than to those of their neo cortexes. Social scientists at major universities have put forth various hypotheses in an attempt to explain why crime has been declining in the United States. One theory is that the US population is aging.

Due to the enormous birth rate increase following WWII, resulting in the famous Baby Boom, the average age of our citizenry has been affected. Thus, in the Fifties we were primarily a nation of children, in the Sixties a totally groovy and far out nation of young people, and so on, to this rather regrettable stage in which we presently find ourselves a nation of senior Boomers.

I would like to be a fly on the wall at a gathering of retired criminals, oldsters spinning their yarns of stick-ups and derring do. Of course you would have to take it all with a grain of salt. Criminals are such liars.

In his Pulitzer-winning book, “Dragons of Eden,” 1977, Sagan popularized neuroscientist Paul D. Maclean’s theory of the evolution of the human brain. According to this theory, the human “triune brain” has evolved from the reptilian brain, enlarged by the paleo, or early, mammalian brain which promotes care of the young, and finally topped off with the neomammalian brain, the neocortex. The neocortex is in charge of language, abstraction, planning, and perception. These structures were added sequentially as the human brain evolved, according to Maclean’s model, and all three brains operate for the most part independently, often in conflict with one another, under the uneasy control of the neocortex.

Since the 1970s, the concept of the triune brain has been subject to criticism in evolutionary and developmental neuroscience, and is regarded as a myth, although I am just finding this out this morning. I for one like the triune brain theory and am sorry to see it go. I read somewhere that it is “popular because of its simplicity.” Well, what’s wrong with the old “occam’s razor” rule, that the simplest solution is usually best?

I’m outnumbered, though. Neuroscientists at the National Institutes of Health (NIH), while perhaps finding Sagan’s popular science amusing, have advised the astrophysicist to stay in his lane. For decades, the concept of the triune brain has been considered inaccurate and is generally regarded as overly simplistic.

Carl Sagan once wrote “We are a way for the cosmos to know itself.” If so, it seems humans provide a way for the cosmos to amuse itself with a lot of nonsense. What will the Cosmos do for entertainment after we have gone?

Have a good week.

(Martha Allen, of Keene Valley, has been writing for the News since 1996.)