How our brains tripled in size compared to our distant chimpanzee ancestors has troubled anthropologists for decades. Many have argued it was the discovery of fire, cooking, hunting, or meat consumption. Most recently, a study suggested it was a boost in omega-3 fatty acids from fish.
While all of these factors may have played a small role in our amazingly large brain size, a new study suggests that not any one event will take all the credit.
The study, published in the Proceedings of the Royal Society, found that the brain size in early hominids enlarged very gradually over millions of years as opposed to quickly after one event. (1)
This study did not make a prediction on what the forces were that supported greater brain size, but certainly limits future and past hypotheses to only those that are compatible with a slow, steady increase rather than sudden, rapid spurts as previously understood. (1,2)
The study tracked fossil records and family lineages of the larger-brained Homo species as well as the smaller-brained hominids, Australopithecus and Paranthropus. The smaller-brained hominids went extinct, which suggests that the branches of evolution that supported larger brains survived more successfully and longer than their smaller-brained cousins.
The Social Intelligence Theory
In 1976, Nicholas Humphrey proposed that social dynamics were the main driver of intelligence which encouraged a larger brain. Instead of climate change, physical environment, cooking, meat or fish, it was theorized that group living and social structures drove intelligence and larger brains. (3) Small clans becoming tribes and eventually small communities drove the brain size to triple.
More recently, a study on the intelligence of birds living in larger or smaller groups was performed. They studied 56 magpies in groups of 3 birds to 12 birds. Instead of measuring brain size, they designed wooden and plastic boxes that required varying degrees of intelligence to open. Researchers found that the larger the size of the group, the more intelligent they were, suggesting that intelligence and brain size may be linked to a social structure of living in larger groups. (3)
Connecting the dots from these studies, we find that we evolved from small family groups that slowly evolved into larger clans, and then tribes. (4) This suggests that the discovery of fire, hunting skills, meat consumption, fishing and cooking may not have been the driver of our larger brains. Rather, the slow and steady growth of clan size, social dynamics resulted in more intelligence and larger brains.
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So, Why Can’t We Get Along?
It’s hard to say if we ever really got along with other tribes as we evolved, but in general, our family clans and tribes did. Living communally depends on the members of the tribe living for and depending on one another and, within the tribe, everyone was safe. Tribes work because every member—from the children to the elders—has an important role to play. These roles weave a social web that provokes creativity, intelligence and, as we now know, larger brains.
Today, we have tribes that provide safe havens for thoughts and beliefs in the form of race, ethnicities, clubs, religions and political affiliations.
Within the walls of your tribe, you are safe and accepted. When we venture out of our tribe, we find ourselves judging the other tribes or recruiting members to join your tribe or trying to convert folks from one club or religion to another.
Maybe it is time to realize that, on this relatively small planet flying through the universe, we are all one tribe. We need to feel safe as a member of this earthling tribe. Each of us live for and depend on each other, and every one of us in this tribe has an important role to play for the good of the tribe as a whole.
Instead of looking for reasons to convert, judge, or attack the beliefs of one clan, race, political party or religion, it’s time to accept each clan as a part of a much greater tribe—planet earth’s human race.