I think the discussion of cultural transmission as source of the ‘sharp left turn’ of human evolution is missing a key piece.
Cultural transmission is not the first causal mechanism. I would argue that it is necessary for the development of modern human society, but not sufficient.
The question of “How did we come to be?” is something I’ve been interested in my entire adult life. I’ve spent a lot of time in college courses studying neuroscience, and some studying anthropology. My understanding as I would summarize it here:
Around 2.5 million years ago—first evidence of hominids making and using stone tools
Around 1.5 million years ago—first evidence of hominids making fires
Around 300,000 years ago (15000 − 20000 generations), Homo sapiens arises as a new subspecies in Africa. Still occasionally interbreeds with other subspecies (and presumably thus occasionally communicates with and trades with). Early on, homo sapiens didn’t have an impressive jump in technology. There was a step up in their ability to compete with other hominids, but it wasn’t totally overwhelming. After out-competing the other hominids in the area, homo sapiens didn’t sustain massively larger populations. They were still hunter/gatherers with similar tech, constrained to similar calorie acquisition limits.
They gradually grow in numbers and out-compete other subspecies. Their tools get gradually better.
Around 55,000 years ago (2700 − 3600 generations), Homo sapiens spreads out of Africa. Gradually colonizes the rest of the world, continuing to interbreed (and communicate and trade) with other subspecies somewhat, but being clearly dominant.
Around 12,000 years ago, homo sapiens began developing agriculture and cities.
Around 6,000 years ago, homo sapiens began using writing.
From wikipedia article on human population:
Here’s a nice summary quote from a Smithsonian magazine article:
For most of our history on this planet, Homo sapiens have not been the only humans. We coexisted, and as our genes make clear frequently interbred with various hominin species, including some we haven’t yet identified. But they dropped off, one by one, leaving our own species to represent all humanity. On an evolutionary timescale, some of these species vanished only recently.
On the Indonesian island of Flores, fossils evidence a curious and diminutive early human species nicknamed “hobbit.” Homo floresiensis appear to have been living until perhaps 50,000 years ago, but what happened to them is a mystery. They don’t appear to have any close relation to modern humans including the Rampasasa pygmy group, which lives in the same region today.
Neanderthals once stretched across Eurasia from Portugal and the British Isles to Siberia. As Homo sapiens became more prevalent across these areas the Neanderthals faded in their turn, being generally consigned to history by some 40,000 years ago. Some evidence suggests that a few die-hards might have held on in enclaves, like Gibraltar, until perhaps 29,000 years ago. Even today traces of them remain because modern humans carry Neanderthal DNA in their genome.
And from the wikipedia article on prehistoric technology:
There are some key defining characteristics. The introduction of agriculture resulted in a shift from nomadic to more sedentary lifestyles,[35] and the use of agricultural tools such as the plough, digging stick and hoe made agricultural labor more efficient.[citation needed] Animals were domesticated, including dogs.[34][35] Another defining characteristic of the period was the emergence of pottery,[35] and, in the late Neolithic period, the wheel was introduced for making pottery.[36]
So what am I getting at here? I’m saying that this idea of a homo sapiens sharp left turn doesn’t look much like a sharp left turn. It was a moderate increase in capabilities over other hominids.
I would say that the Neolithic Revolution is a better candidate for a sharp left turn. I think you can trace a clear line of ‘something fundamentally different started happening’ from the Neolithic Revolution up to the Industrial Revolution when the really obvious ‘sharp left turn’ in human population began.
So here’s the really interesting mystery. Why did the Neolithic Revolution occur independently in six separate locations?!
Here’s my current best hypothesis. Homo sapiens originally was only somewhat smarter than the other hominids. Like maybe, ~6-year-old intelligences amongst the ~4-year-old intelligences. And if you took a homo sapiens individual from that time period and gave them a modern education… they’d seem significantly mentally handicapped by today’s standards even with a good education. But importantly, their brains were bigger. But a lot of that potential brain area was poorly utilized. But now evolution had a big new canvas to work with, and the Machiavellian-brain-hypothesis motivation of why a strong evolutionary pressure would push for this new larger brain to improve its organization. Homo sapiens was competing with each other and with other hominids from 300,000 to 50,000 years ago! Most of their existence so far! And they didn’t start clearly rapidly dominating and conquering the world until the more recent end of that. So 250,000 years of evolution figuring out how to organize this new larger brain capacity to good effect. To go from ‘weak general learner with low max capability cap’ to ‘strong general learner with high max capability cap’. A lot of important things happened in the brain in this time, but it’s hard to see any evidence of this in the fossil record, because the bone changes happened 300,000 years ago and the bones then stayed more or less the same. If this hypothesis is true, then we are a more different species from the original Homo sapiens than those original Homo sapiens were from the other hominids they had as neighbors. A crazy fast time period from an evolutionary time point, but with that big new canvas to work with, and a strong evolutionary pressure rewarding every tiny gain, it can happen. It took fewer generations to go from a bloodhound-type-dog to a modern dachshund.
There are some important differences between our modern Homo sapiens neurons and other great apes. And between great apes vs other mammals.
The fundamental learning algorithm of the cortex didn’t change, what did change were some of the ‘hyperparameters’ and the ‘architectural wiring’ within the cortex.
For an example of a ‘hyperparameter’ change, human cortical pyramidal cells (especially those in our prefrontal cortex) form a lot more synaptic connections with other neurons. I think this is pretty clearly a quantitative change rather than a qualitative one, so I think it nicely fits the analogy of a ‘hyperparameter’ change. I highlight this one, because this difference was traced to a difference in a single gene. And in experiments where this gene was expressed in a transgenic mouse line, the resulting mice were measurably better at solving puzzles.
An example of what I mean about ‘architectural wiring’ changes is that there has been a shift in the patterns of the Brodmann areas from non-human apes to humans. As in, what percentage of the cortex is devoted to specific functions. Language, abstract reasoning, social cognition all benefited relatively more compared to say, vision. These Brodmann areas are determined by the genetically determined wiring that occurs during fetal development and lasts for a lifetime, not determined by in-lifetime-learning like synaptic weights are. There are exceptions to this rule, but they are exceptions that prove the rule. Someone born blind can utilize their otherwise useless visual cortex a bit for helping with other cognitive tasks, but only to a limited extent. And this plastic period ends in early childhood. An adult who looses their eyes gains almost no cognitive benefits in other skills due to ‘reassigning’ visual cortex to other tasks. Their skill gains in non-visual tasks like navigation-by-hearing-and-mental-space-modeling come primarily from learning within the areas already devoted to those tasks driven by the necessity of the life change.
What bearing does this have on trying to predict the future of AI?
If my hypothesis is correct, there are potentially analogously important changes to be made in shaping the defining architecture and hyperparameters of deep neural nets. I have specific hypotheses about these changes drawing on my neuroscience background and the research I’ve been doing over the past couple years into analyzing the remaining algorithmic roadblocks to AGI. Mostly, I’ve been sharing this with only a few trusted AI safety researcher friends, since I think it’s a pretty key area of capabilities research if I’m right. If I’m wrong, then it’s irrelevant, except for flagging the area as a dead end.
For more details that I do feel ok sharing, see my talk here:
So, I think the real ‘sharp left turn’ of human history was the Industrial/Scientific Revolution. But that needed a lot of factors to happen. Necessary but not sufficient ingredients like:
Brains which could do the necessary abstract thinking
Brains which could do the necessary communication of ideas across time and space
Critical mass of humanity and specialization of civilization to allow for enough smart thinkers with enough time to do the needed communication and thinking
Initial ideas occurring to some subset of the thinkers, to kickstart the process
Economic pressures pushing more attention and energy into the project of accelerating scientific understanding and technological development
Copying my response agreeing with and expanding on Jan’s comment on Evolution Provides No Evidencefor the Sharp Left Turn.
I think the discussion of cultural transmission as source of the ‘sharp left turn’ of human evolution is missing a key piece.
Cultural transmission is not the first causal mechanism. I would argue that it is necessary for the development of modern human society, but not sufficient.
The question of “How did we come to be?” is something I’ve been interested in my entire adult life. I’ve spent a lot of time in college courses studying neuroscience, and some studying anthropology. My understanding as I would summarize it here:
Around 2.5 million years ago—first evidence of hominids making and using stone tools
Around 1.5 million years ago—first evidence of hominids making fires
https://en.wikipedia.org/wiki/Prehistoric_technology
Around 300,000 years ago (15000 − 20000 generations), Homo sapiens arises as a new subspecies in Africa. Still occasionally interbreeds with other subspecies (and presumably thus occasionally communicates with and trades with). Early on, homo sapiens didn’t have an impressive jump in technology. There was a step up in their ability to compete with other hominids, but it wasn’t totally overwhelming. After out-competing the other hominids in the area, homo sapiens didn’t sustain massively larger populations. They were still hunter/gatherers with similar tech, constrained to similar calorie acquisition limits.
They gradually grow in numbers and out-compete other subspecies. Their tools get gradually better.
Around 55,000 years ago (2700 − 3600 generations), Homo sapiens spreads out of Africa. Gradually colonizes the rest of the world, continuing to interbreed (and communicate and trade) with other subspecies somewhat, but being clearly dominant.
Around 12,000 years ago, homo sapiens began developing agriculture and cities.
Around 6,000 years ago, homo sapiens began using writing.
From wikipedia article on human population:
Here’s a nice summary quote from a Smithsonian magazine article:
And from the wikipedia article on prehistoric technology:
So what am I getting at here? I’m saying that this idea of a homo sapiens sharp left turn doesn’t look much like a sharp left turn. It was a moderate increase in capabilities over other hominids.
I would say that the Neolithic Revolution is a better candidate for a sharp left turn. I think you can trace a clear line of ‘something fundamentally different started happening’ from the Neolithic Revolution up to the Industrial Revolution when the really obvious ‘sharp left turn’ in human population began.
So here’s the really interesting mystery. Why did the Neolithic Revolution occur independently in six separate locations?!
Here’s my current best hypothesis. Homo sapiens originally was only somewhat smarter than the other hominids. Like maybe, ~6-year-old intelligences amongst the ~4-year-old intelligences. And if you took a homo sapiens individual from that time period and gave them a modern education… they’d seem significantly mentally handicapped by today’s standards even with a good education. But importantly, their brains were bigger. But a lot of that potential brain area was poorly utilized. But now evolution had a big new canvas to work with, and the Machiavellian-brain-hypothesis motivation of why a strong evolutionary pressure would push for this new larger brain to improve its organization. Homo sapiens was competing with each other and with other hominids from 300,000 to 50,000 years ago! Most of their existence so far! And they didn’t start clearly rapidly dominating and conquering the world until the more recent end of that. So 250,000 years of evolution figuring out how to organize this new larger brain capacity to good effect. To go from ‘weak general learner with low max capability cap’ to ‘strong general learner with high max capability cap’. A lot of important things happened in the brain in this time, but it’s hard to see any evidence of this in the fossil record, because the bone changes happened 300,000 years ago and the bones then stayed more or less the same. If this hypothesis is true, then we are a more different species from the original Homo sapiens than those original Homo sapiens were from the other hominids they had as neighbors. A crazy fast time period from an evolutionary time point, but with that big new canvas to work with, and a strong evolutionary pressure rewarding every tiny gain, it can happen. It took fewer generations to go from a bloodhound-type-dog to a modern dachshund.
There are some important differences between our modern Homo sapiens neurons and other great apes. And between great apes vs other mammals.
The fundamental learning algorithm of the cortex didn’t change, what did change were some of the ‘hyperparameters’ and the ‘architectural wiring’ within the cortex.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3103088/
For an example of a ‘hyperparameter’ change, human cortical pyramidal cells (especially those in our prefrontal cortex) form a lot more synaptic connections with other neurons. I think this is pretty clearly a quantitative change rather than a qualitative one, so I think it nicely fits the analogy of a ‘hyperparameter’ change. I highlight this one, because this difference was traced to a difference in a single gene. And in experiments where this gene was expressed in a transgenic mouse line, the resulting mice were measurably better at solving puzzles.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10064077/
An example of what I mean about ‘architectural wiring’ changes is that there has been a shift in the patterns of the Brodmann areas from non-human apes to humans. As in, what percentage of the cortex is devoted to specific functions. Language, abstract reasoning, social cognition all benefited relatively more compared to say, vision. These Brodmann areas are determined by the genetically determined wiring that occurs during fetal development and lasts for a lifetime, not determined by in-lifetime-learning like synaptic weights are. There are exceptions to this rule, but they are exceptions that prove the rule. Someone born blind can utilize their otherwise useless visual cortex a bit for helping with other cognitive tasks, but only to a limited extent. And this plastic period ends in early childhood. An adult who looses their eyes gains almost no cognitive benefits in other skills due to ‘reassigning’ visual cortex to other tasks. Their skill gains in non-visual tasks like navigation-by-hearing-and-mental-space-modeling come primarily from learning within the areas already devoted to those tasks driven by the necessity of the life change.
https://www.science.org/content/blog-post/chimp-study-offers-new-clues-language
What bearing does this have on trying to predict the future of AI?
If my hypothesis is correct, there are potentially analogously important changes to be made in shaping the defining architecture and hyperparameters of deep neural nets. I have specific hypotheses about these changes drawing on my neuroscience background and the research I’ve been doing over the past couple years into analyzing the remaining algorithmic roadblocks to AGI. Mostly, I’ve been sharing this with only a few trusted AI safety researcher friends, since I think it’s a pretty key area of capabilities research if I’m right. If I’m wrong, then it’s irrelevant, except for flagging the area as a dead end.
For more details that I do feel ok sharing, see my talk here:
So, I think the real ‘sharp left turn’ of human history was the Industrial/Scientific Revolution. But that needed a lot of factors to happen. Necessary but not sufficient ingredients like:
Brains which could do the necessary abstract thinking
Brains which could do the necessary communication of ideas across time and space
Critical mass of humanity and specialization of civilization to allow for enough smart thinkers with enough time to do the needed communication and thinking
Initial ideas occurring to some subset of the thinkers, to kickstart the process
Economic pressures pushing more attention and energy into the project of accelerating scientific understanding and technological development
A relevant comment from RogerDearnaley: https://www.lesswrong.com/posts/wCtegGaWxttfKZsfx/we-don-t-understand-what-happened-with-culture-enough?commentId=zMTRq2xoCfc7KQhba
Potentially relevant: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9915799/