Introducing the brain: why so big? Part two (Introduction)

by David Turell , Thursday, July 11, 2024, 22:07 (133 days ago) @ David Turell

Directly continued:

https://www.newscientist.com/article/mg26334991-100-why-did-humans-evolve-big-brains-a-...

"At the same conference, Weber presented an analysis showing that the rate of brain expansion hasn’t been constant, though. Between 7 million and 2 million years ago, average hominin brains increased modestly in size – from about 360 to 450 cubic centimetres. Then they enlarged at a faster rate, ballooning to 1350 cubic centimetres 110,000 years ago. After that, the rate accelerated even further, with brain volume reaching a peak of 1500 cubic centimetres around 50,000 years ago, late in the Stone Age.

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'An alternative hypothesis does address the question of why. It states that some hominins began living in bigger social groups and grew larger brains to cope. “If your social environment is more complex, you may need a bigger brain to understand how to live with that complexity,” says Beaudet. But there are problems with this idea too. For instance, it implies that brain size should correlate with social group size across primate species – but researchers have failed to find this pattern.

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"...as brains grew larger, the population would have found it even easier to improve their tool-making and language skills, leading to further selection for larger brains and making tool production easier still. “Evolution doesn’t just invent new brain structures and suddenly you can speak or whatever. It’s the other way round,” says Christoph Zollikofer at the University of Zurich in Switzerland. “You start speaking and then this creates a new cultural environment under which there are new selective pressures that favour new brain structures.”

"This still doesn’t explain why bigger brains would have made tool-making or language easier to master...Purely by chance, some of these connections might have made it easier for humans to talk or make tools. In other words, brain expansion may initially have had no survival advantage, but then serendipitously acquired one – at which point natural selection would have kicked in.

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"...size clearly matters at least to some extent, which raises questions about a curious event in our recent evolutionary history when brains shrank, going from 1500 cubic centimetres to just 1350 cubic centimetres – the volume we have today. Surprisingly, this shrinking may have had the same underlying cause as brain growth: the development of new technologies and sophisticated behaviours.

"In a 2021 study, DeSilva and his colleagues analysed data from hundreds of ancient skulls to work out exactly when this shrinking event occurred. “We were surprised how recent it was: within the 3000-to-5000-year range,” he says. This suggests brains downsized at a pivotal moment – just as the first civilisations began to appear and new technologies, including writing, emerged.

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"Even if human brains shrank in the past as individuals began to rely more heavily on new technologies, humans clearly continued to flourish. Beaudet thinks we should view AI as the latest in a long line of hominin technologies, stretching back to the pounding stones our ancestors used to process food. Just like those stone tools, AI might simply improve the efficiency with which we carry out certain tasks, affording us more time to dream up even more technologies. “It’s been like this since the beginning of the human story and I think it will never stop,” she says. “I am a bit worried, but I don’t think AI will rule the world.”

Comment: a jumbo article filled with just-so conjectures to explain the phenomenon of our big brain. The size discussion ignores the complexity issue in which a smaller brain can be more highly complex and produce unexpectedly advanced products (artifacts). Our bigger brain event to smaller brain by 150 cc average is right on point. Throughout the article no explanation appears that ever answers the question: Viewed as a natural event how do our brain get big? Adler's supernatural answer: God.