One of the fascinating aspects of life is when you look at an animal, at least with large multicellular animals you usually can see why the animal is there. It either has big fangs, tough skin, massive muscles, night vision, immunities to poisons and diseases, and/or all of the above. But what about humans? Humans have soft skin, no fangs, muscle mass isn't the most competitive attribute against other animals. What's even more striking is that humans are bipedal, no other ape is bipedal.
If we look at the mini-chimpanzee, the Bonomo, we see atrophying of muscle mass and large fangs, why? Well Bonomos did something different in their evolution, they shifted their social dynamic to settle conflicts through sexual gratification. Imagine you're angry at a peer member, you want to tell them exactly what you think about them and how upset you are about what they say and do. As you approach the individual you're upset with you suddenly get an overwhelming urge to have sex with them. Ultimately you do and after all, is said and done you're no longer angry and you and this individual you had issues with are now willing to cooperate to resolve any issues!
Obviously, something in the Bonomo's brain wiring is different than what is seen in chimpanzees and even hominids. The results are manifested in the ape's physiology. Because of a change in brain wiring, perhaps some high degree of innervation from the Amadyla to the anterior cingulate cortex (ACC), the thalamus, the parietal cortex and the hypothalamus where sexual arousal is produced, the ape can no longer fight, particularly a fight to the death, which is what we see in chimpanzees and hominids.
But how does this explain anything about humans? One of the biggest problems anthropologists face with human evolution is why are hominids bipedal? Some theories suggest tree scarcity is the cause because there are fewer trees to get from one tree to the next walking proved the better choice. Another theory is field of view because a bipedal animal has a better view of predators and prey it can avoid being eaten while at the same time find its prey very easily. But as I said earlier you can usually see why an animal exists in its environment, there's that feature or set of features that clearly explains why the animal is successful in its environment. So what could it be for humans, well most would say it's their big brains that give them the ability to solve problems more effectively and build tools. OK, but Astralopethicus has a brain the size of a chimp, yet all of its fangs, claws, and muscle mass paired down to something that could never compete with other animals.
So what is it about Australopithecus that allowed it to not need the biological weaponry that other animals have, similarly to the Bonomo? Well, what about stone-throwing? Yes, it is seen in other primates and apes, but most do an underhand throw. If you remember ever playing baseball or stone skimming the first thing you learn is you don't just use your arm to throw that stone, not if you want the highest velocity that you can throw it! So what does a child learn to do to get a stone to travel farther and faster? You learn to use your entire body to throw that stone. You use your legs, torso, arms, and wrist to throw that stone to get it to move a fast as you can possibly through it. If it weren't for hominids proportionally longer legs than other apes we couldn't really effectively through stones to velocities reaching over a 100 mph! Now when you look at the human body and realize that Australopithecus was very very similar in proportions then it hits you like a rock over the head! Australopithecus was a stone-throwing ape that learned to use its entire body to throw the stone to get the highest velocity possible. This stone-throwing skill was used to hunt prey. Other animals inclusive of chimpanzees pounce their prey which takes a phenomenal amount of energy. Australopithecus can hunt by simply throwing a stone. This makes Australopithecus the most efficient hunter on the planet! It only takes a fraction of the energy to throw a stone as opposed to moving an entire body to chase prey. Not only that but it gives it the ability to take down prey at distances where the target prey would not find them to be a threat so the animals don't run away. Australopithecus is hunting small prey, not larger animals with stone-throwing. Now bipedalism makes sense! The animal that could use its entire body to throw stones at high velocities gets more protein with the least effort where he/she has more time and resources to reproduce.
Now we can see why bipedalism took over in the hominid legacy and with so many efficient hunters most have more than enough protein to sustain their bodies and then some. Where in a chimpanzee society those with the most protein are the larger and stronger apes that rule the troop, but with Australopithecus, all have access to protein resources so it doesn't have the same impact in the social order of their societies. Because of the easy access to protein Australopithecus had to compete on a whole different level and that forum was social intelligence, now the game turned from the strongest ape in the jungle to the most charming ape in the jungle.
When looking at our own evolution it wasn't the biggest brained ape that managed to survive east Africa's hot Savana, it was a bipedal ape. And just as in the Bonomo where a brain wiring change led to a different social dynamic that then leads to smaller, less weaponized bodies, so too do we see that hominids by virtual of bipedalism led to more efficient hunting that forced a form of competition that favored less muscular and large fanged bodies to more socially adept individuals. Such social adeptness, at least in humans, maybe due to the wiring of the Arcuate Fasciculus which interconnects frontal and temporal language areas. Chimpanzees have very few fibers in the Arcuate Fasciculus that extend to the superior temporal sulcus which is where word meaning is represented in human brains and Macaques do not have an Arcuate Fasciculus. I'm asserting that Australopithecus had a higher density of fibers interconnecting Arcuate Fasciculus that extend to the superior temporal sulcus than chimpanzees or any other ape for that matter.
So what has this to do with finding intelligent life on other worlds? First and foremost is the emphasis for the criteria of what would re-enforce large brains? While I assert that it was due to bipedalism and a re-wiring of a brain other environments might favor a different path to sophisticated intelligent beings. So just by looking at our environment where such favoritism for large brains is rare and biological weaponry is the defacto standard, other worlds might not be so harsh for large brains. There might be worlds that favor large brains over biological weaponry or at least favor bigger brains more frequently...
