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The brain as an organ - The human brain is a complex organ that controls every function of the body, from thought and memory, to vision, breathing, and temperature.

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A common conception -

People like to think there is a positive correlation between brain size and cognitive function. That is to say, the bigger the brain the more powerful it will be.

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And the logic behind it -

This belief perhaps stems from an understanding that a bigger brain has more neurons, and therefore can operate with higher power and function.

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Natural conclusion - By that logic, we would expect the human brain to have grown in size as the human species has evolved. We have become more intelligent, so we should have bigger brains, right?

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Surprising findings -

According to recent discoveries, however, it seems that is not the case. Emerging research has prompted scientists to question their understanding of the brain.

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The study - In 2021, a team of anthropologists at Dartmouth College published a study that suggests the human brain has shrunk by the equivalent of four ping pong balls in the last 3,000 years.

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The confusion -

This has left researchers puzzled, since it was around this time that huge technological progress was made. For the first time, humans walked around and formed complex civilizations.

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Possible explanations -

Researchers have come up with a number of hypotheses to explain why the size of the average human brain has dwindled over the course of these three millennia.

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Unlikely source of inspiration -

The first hypothesis is based, somewhat surprisingly, on what we know about the brains of ants. Despite the obvious difference in size, the brains of some species of ant are strikingly similar to ours.

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Ant agriculture -

In fact, some ant species even practice a form of agriculture, which involves their growing and harvesting huge amounts of fungus inside their nests.

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The discovery -

The anthropologists from Dartmouth studied the brain size of a number of ant species and found that those in large societies had bigger brains, unless they also had the agricultural ability.

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The conclusion -

This suggests, in turn, that more complex social systems might cause ant brains to shrink, perhaps because there is a greater division of labor and cognitive capabilities are divided.

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Human application -

This discovery prompted the researchers to question whether the same thing happened in humans; whether at some point we began to share and externalize information in the brains of others.

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Caveat -

Of course, there are huge differences between human and ant brains, so any parallels between the two should be drawn with great caution.

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Another hypothesis -

Another hypothesis for why the human brain has shrunk is related to the emergence of writing. We began putting pen to paper around 5,000 years ago, two millennia before the shrinkage.

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The impact of writing -

Researchers have questioned whether the emergence of the possibility to put thoughts down on paper, and therefore externalize them, could have had an impact on brain volume.

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Concluding the hypotheses - For now, these are the most credible theories as to why the human brain has gotten smaller over the last 3,000 years.

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Other theories -

There are other theories out there, but these are quickly discredited if we accept that the shrinkage only began as recently as 1000 BCE.

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Domestication -

For example, it was thought for a while that domestication might have caused our brains to get smaller. We see this in many other species, after all.

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Debunked - However, human domestication occurred tens, if not hundreds, of thousands of years ago, so the timelines just don’t add up.

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Another question -

For now, the question as to why our brains are smaller than our ancestors remain unanswered. But there is another important question to consider: does bigger actually mean better?

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Is bigger always better? -

As described earlier, we often correlate brain size with brain power. We like to think that people with bigger brains are somehow smarter.

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Not necessarily -

The reality is, however, that a bigger brain doesn’t really make for a smarter person, unless the conversation is about tiny differences across a vast population.

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The study -

In 2018, a team of researchers studied the brain size and IQ of 13,600 people. It found, on average, that those participants with bigger brains did slightly better on IQ tests.

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Findings -

Crucially, however, the relationship was non-deterministic. Some participants scored very high on the IQ test despite having a smaller brain, and vice versa.

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Verbatim - To quote Philipp Koellinger, co-author of the study, “There is really no strong relationship. It is just all over the place.”

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Structural features -

It might also be the case that other structural features have a material impact on a person’s intelligence.

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Gray matter -

For example, some research shows that a higher level of gray matter—the outer layer of the brain—makes for a higher IQ.

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All in all -

There is still a huge amount we don’t know about the brain, but the general consensus is that structural differences are more likely to impact intelligence than sheer size.

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What does it mean? -

We know that the brain has shrunk to its current size over the last 3,000 years. But will it continue to shrink, and what does that mean for our species?

Sources: (BBC)

See also: Are you left-brained or right-brained?

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