The Rise of The Hominid Mind — A Thought Experiment
When I was in high school, an English teacher and I had a discussion on the topic of human evolution. At one point she asked me why only the line of primates that lead to modern humans developed the advanced intelligence that sets humans apart. After all, many primates are somewhat intelligent, but there is still a vast difference between beasts and humans.
At first, I misunderstood her question, thinking that she was asking the naive “If we all came from monkeys, then why are there still monkeys?” question that ill-informed critics of Evolution often ask. I began to explain that Evolution is a branching process and that we would not expect a separate branch of primates to repeat the process of evolving into humans. But she clarified her question.
The question was not why modern primates don’t evolve into humans, but why modern primates haven’t evolved into sapient species the way our ancestors did. In other words, why did Chimps, Gorillas, Lemurs and other nonhuman primates not evolve a higher intelligence? Why do we not see a Planet of The Apes type of scenario with several species of highly intelligent primates, instead of just one?
When I understood what she was actually asking, I thought about it and realized it was a very good question. It was not so much an objection to human evolution, but a question of why things have evolved in a certain way.
Clearly, intelligence comes with plenty of advantages. Advantages that should be favored by natural selection — all other things being equal.
In recent months, I have been thinking about this question more and I think that I’ve come up with some potential answers to this puzzling question.
Early Australopithecines And The Rise of The Mind
I’ve heard quite a few speculations about why our early ancestors would have developed larger and more complex brains. Some of these included the idea that changes in the jaw size allowed a larger brain to grow, others included the idea that a high-fat diet made intelligence possible. Certainly, a combination of these sorts of changes could have contributed to our evolution however, such superficial explanations leave a lot to be desired. Plenty of animals enjoy a high-fat or high-calorie diet but clearly have not evolved a great deal of intelligence. And something as superficial as a change in jaw shape is bound to have occurred many times in many mammalian clades, but without creating something with a high level of intelligence.
But in all of the discussions I have heard, there are other more important factors than these which seem to be overlooked.
Let’s look at what we know about Australopithecines. Lucy, the most famous member of these organisms was only around three feet tall, with a skull very much like an ape, along with hips very similar to those of a human — but proportionate to the size of this individual.
So we have a three-foot-tall ape that stands erect like a modern human, and which has probably lost much of its tree-climbing ability, but without the large sophisticated brain of a modern human. This sounds like an easy meal for an apex predator like a lion or even for another primate — a thing more likely to die out than to dominate the planet.
But here is the one core clue that I was missing: The size of the brain is not a direct indicator of the sophistication of the mind. We see this even in modern humans. One human may have a much smaller brain than another, and yet the human with the smaller brain may be much smarter.
Lucy’s kind may not have had the ability to create iPhones, but they did not need to. They only had to be smart enough to outplay the lion. One lion against one Lucy is like a cat with a mouse. But one lion against 20 Australopithecines coordinating with one another using primitive language along with primitive stone tools and sticks that act as spears may have been a formidable enough challenge. Even if the lion could take them and be successful, he may not want to.
It’s the same type of advantage we see with a honey bee. One stingerless bee is no cause for concern, however, few predators would approach a well-coordinated hive of bees cooperating with one another, and armed with stingers. In the case of our ancestors, relative intelligence may have provided both the ability to coordinate and to use primitive weapons.
The World of The Lucies
Even with this thought experiment, I still had a few other questions. Namely, what would drive evolution towards high intelligence in this instance, but not in others? What was it that so affected our early ancestors that this was the time that a living organism here on Earth was driven towards a higher intelligence than anything that has ever been documented?
I figured this must have something to do with the environment.
It’s easy to forget that the number one limiting factor for an organism may not necessarily be the amount of food available. There are many other selective pressures that any species has to face.
I imagine that the world an upright primate with an emerging intelligence might face is one with fewer trees, hence the trend toward an erect posture. Perhaps an upright posture also played a role in intimidating certain predators or other early hominids/primates.
I also imagine that this would have been an environment with an abundance of available dietary calories. After all, intelligence is very expensive in terms of energy, and this may be a major part of why most higher animals have not evolved beyond a certain level of intelligence, and why we often see a relative stasis in this area (perhaps a form of stabilizing selection), even when other traits readily evolve to fit any number of environments.
Perhaps there were tubers and other foods that early hominids had access to, meaning that calories weren’t a limiting factor in evolving intelligence. One of the interesting things I’ve noticed about modern humans is our ability to used a large number of plants, animals, and fungi as food sources. Maybe our ancestors and their relatives did the same.
But even with the raw materials needed to fuel the evolution of the brain (fat, protein, calories), there still had to be something in the environment to select for successively higher and higher levels of intelligence. The obvious drive might be predators (perhaps the lion) but it might also be an evolutionary “arm’s race” between these emerging intelligent species, or even within individual species. Perhaps having a slightly higher IQ than the other guy gave some advantage, and an abundance of calories and food meant that the trade-off of a more complex brain was minimized. The advantage gradually outweighed the disadvantage. The smartest hominid might have become “king of the hill” in some way or another.
This might mean that selection would drive evolution in one direction through a gradual “herding” process (like a shepherd with sheep) but without causing extinction.
The result might be a scenario of a “Survival of the cleverest” which is a necessary factor if an emerging sapience is to span the intellectual chasm between a beast and something like a man.
Various limiting factors may prevent animals from achieving sapience (human-like intelligence). This may be various types of stabilizing selection. Perhaps an eagle simply has the appropriate level of intelligence for its own niche.
Or it may be something as simple as the lack of evolutionary potential in terms of the evolvability of the brain. A spider is a cool animal, but it may not have room for a significantly more complex brain.
There may also be a simple lack of drive in pushing evolution in this direction for many species — higher intelligence may simply not add a huge benefit to their reproductive success in their given niche. Wild cattle eat grass, walk around, mate, give birth, and run away from predators. But a brain twice as complex, even without the costs, may not do anything for the wild cow.
Any or all of these factors may apply to nonhuman primates.
But whatever it was, something gradually drove our ancestors in the direction of true sapience. As far as we know, we are the only species to be molded in this way.
Perhaps in the future, when humans colonize other solar systems, we will have the ability to run million-year long experiments to test these hypotheses. But for now, a thought experiment, along with some paleoanthropology and phylogenetics will keep us quite busy.
My goal with this article is only to play with this thought experiment. I don’t want to make more of this than what it is. A lot of what I propose here is armchair speculation, but speculation is often the first step in any intellectual pursuit. Without this first step, we would never go anywhere. Gould rightly pointed out the criticism that we should not conflate “just so” stories with empirical science. And he was right, speculation is not data, but perhaps there is something important here.
I also want to be careful about overinterpreting the data that we have. Lucy and similar specimens are certainly tantalizing, but it’s entirely possible that she represents a divergent branch in our evolutionary family tree. Our actual ancestors that were contemporaries with Lucy may have been quite different from this now-extinct hominid species.
In my opinion, speculation has its place, along with simulations, however, these ideas need to be tested against the empirical data. The way I would approach this and other questions surrounding human evolution would be to start with phylogenetics analysis and to seek to better understand how various molecular mechanisms play a role in evolutionary adaptation. Random point mutations followed by natural selection have obviously played a role, but a 21st Century understanding of transposable elements, gene duplication, and rearrangement along with other mechanisms are going to be key in developing a fuller understanding of what made us human.
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