Hi, I'm Tim Tyler - and this is a video about the big brain as a meme nest - and in it we will discuss the hypothesis that the human brain has enlarged and expanded over millions of years in order to become spacious accomodation for numerous memes.
Susan Blackmore pioneered the hypothesis that the human big brain is actually an adaptation for storing memes. She has a whole chapter (called "The big brain") on this hypothesis in her 1999 book The Meme Machine.
At first glance, the idea that the enlarged human cranium might be an adaptation for housing mutualist symbiont visitors is an astonishing and counter-intuitive one.
However, culture and co-evolution with memes has resulted in most of the main ways in which we differ from chimpanzees. Memes are, on verage beneficial. As a result of this, humans feature adaptations that are oriented towards hosting their memes - ultrasociality, incessant babbling, and an enlarged cranium to act as a home for all them. It actually makes a lot of sense for our large brain to be a home for memes - in much the same way that Domatia in plants provide housing for ants or alder tree root nodules provide homes for nitrogen fixing bacteria.
In my Memetics book - which is out now - I compare and contrast the meme idea with other hypotheses which purport to explain the big brain - including the Machiavellian intelligence hypothesis and the idea that sexual selection was involved.
The Machiavellian intelligence hypothesis is one of the more popular ideas. However, it doesn't really explain why our brains blew up, while chimpanzee brains did not. What humans have that chimpanzees mostly don't is language, tools and culture.
It is interesting that the mental machinery that people use to model and understand other people in order to help them interact socially is the very same mental apparatus that is needed to imitate their behaviour - and thereby transmit culturally-inherited traits.
The oldest archaeological sites containing tools are dated to 2.6-2.55 million years ago - around the beginning of the stone age - which is an excellent match for when the human brain first really started to inflate. Timing considerations provide significant support to the meme theory.
Susan Blackmore presented her "big brain" hypothesis in 1997. In her 1999 book, she proposed:
that being good at imitation requires a big brain.
She then goes on to predict that imitation ability is likely to be correlated with brain size and writes:
If these predictions turn out to be right they will confirm the suggestion that imitation is an enormously demanding task, and that it takes a large brain to be able to do it.
However, this idea is not supported very well by the evidence from other animals that some forms of imitation are rather easy to perform. To rectify this problem, I have come up with another idea - which is that the human brain rapidly filled up with large numbers of memes - and then selection favoured bigger brains because they could hold more memes.
If memes are beneficial, on average, then many memes will be better than a few memes. If you are wooing a prospective mate with love songs, it helps to have a bit of a repertoire. If you are attracting attention by dancing in front of a fire, it helps to have a range different moves. Knowledge of different fruits, medicines, traps, and lairs all take up space in the brain. Many of our ancestors' heads would have quickly became full to the brim with memes. Initially, a tribe's memes would have been essentially confined to a single human skull. For hunter gatherers, there was little specialisation and - apart from some sexual differences and the medicine man - most people carried copies of most of the tribe's memes. As soon as the memes were able to, they created division of labour, so that different heads could come to contain different memes. That massively expanded the number of different types of meme that society could collectively support. Then, the memes burst forth from the human skull, expanding onto stone tablets, caligraphic volumes, printed pages, and ultimately the internet. The rapidity and force of this outpouring may give some indication of how cramped even the enlarged human cranium was as a meme womb.
Under this hypothesis, the brain did not expand because larger brains could imitate better. It expanded because a huge population of memes living in cramped conditions resulted in selection favouring humans with bigger brains that provided larger living quarters which were capable of supporting memes in greater numbers.
For references, see my big-brains-as-meme-nests essay.