I see there are new fossil finds in Morocco which have been reported on the BBC. Here is the Nature Letter that reports the new find. What were modern humans up to prior to the flowering of human civilisation that left no mark prior to, lets say, ten thousand years ago? Why the large brains? Why the capacity for complex communication? Why the gap of over a quarter of a million years before the burst into human civilisation?
103 thoughts on “Human Evolution: the evidence evolves!”
Leave a Reply
You must be logged in to post a comment.
Not-farming.
Wish I could provide anecdotal evidence of sexual selection.
Are you implying that hunter-gatherers, including modern hunter-gatherer societies, don’t use their large brains? On what basis could you possibly say that?
That seems clear enough. The invention of agriculture, allowing dense, sedentary populations. I suppose you could rephrase the question: why did it take so long for agriculture to be invented?
I’ve got anecdotal evidence of sexual selection all over the place. The brights seem to have a lot of trouble locating partners. I have a relative who isn’t too bright. She produced 5 children by 5 different men. She is the child of a woman who did the same. It may have been different in a different time, but right now the dumbs are beating the brights hands down in sexual selection.
Humans have been around for a long time. The ability to raise children without doing productive work is something new.
“Very bright” has to be defined in context. A bunch of PhDs might perish pretty quickly in a world where physical strength rules.
And the other apes survived alongside humans without being able to read or compute.
another reason for no signs of humans before 10000 years ago was because there was no humans or a earth. that would be more likely then long periods of doing nothing.
There is no evidence, only presumed, that large brains are relevant to intelligence. there is no evidence, i say, we have brains as the source of intelligence.
The communication is not complex. Its the thinking that is complex. The communications is dumb sounds and signs(facial/hands etc
We never had complex thoughts and couldn’t express it in languages. We never had a complex language without complex thoughts.
Smart from the start and gabby.
Civilization? Well a few of them I guess on a curve. are we civilized now ?
I’m puzzled by these questions. Is the thought supposed to be that there’s some obvious tie between civilization and intelligence, so the energence of human-type intelligence thousands of years before civilization is supposed to be mysterious, or at least a problem to be solved?
The energence of human levels of intelligence thousands of years before civilization doesn’t seem puzzling to me. Not at all.
Some of them were painting on the walls of caves
I’m puzzled as well. The pre-adaptations that allowed advanced communication and tool innovation were millions of years in the making. On an evolutionary time-scale, I doubt that our brains have changed much in the last hundred thousand years. However, our ability to share and accumulate knowledge has allowed a staggering increase in technology since the Neolithic revolution.
Don’t want to sound like an ancient astronaut kook, but I keep wondering how much human history was erased by the glaciers, and how many seacoast settlements or cities were erased by rising oceans after the ice age.
In the context of civilized society, I’m not sure whether differential reproductive success will matter within our species (at least until the climate is bad enough to seriously limit food production). It will probably just continue to exacerbate economic inequality as the uneducated many produce large quantities of children for which they can barely provide while the more educated few limit their breeding and invest more in a single child to give them better opportunities for success.
Differential reproductive success, by definition, matters.
What may not matter as much are things we usually associate with selection, like health and intelligence.
We apparently tend to think that “survival of the fittest” is what is going on, and that the fittest means something objective and distinct from the fact of reproduction. That is not the case.
petrushka,
I disagree, albeit mildly. Until such a time as all civilized infrastructure has collapsed and we are individually competing for food and clean water, I don’t personally think that reproductive rates matter terribly much. The upper few percentile of the population (economically speaking) will continue to generally come from well-educated families with a low birth rate. As long as that group does not become so small as to start in-breeding like Medieval Royalty, they will enjoy a longer than average life-span due to better healthcare, better working conditions, etc.
I doubt that the difference in birth rates between the ‘brights’ and ‘not-so brights’ will have any effect whatsoever upon the species simply because I don’t think that the term ‘survival’ is relevant in any meaningful way. The species will continue and the only thing that will change will be the distribution of subsets of society at different socio-economic levels.
Hi Alan,
You ask:
Let me pick up the story from the time of Heidelberg man, the presumed common ancestor of modern humans, Neandertals and Denisovans, whose brain was significantly larger than that of Homo ergaster / erectus.
The first reason for our ancestors’ acquiring a large brain may have been self-control, or more specifically, the ability to control one’s inhibitions and stay focused on one’s goal. In his article, Paleolithic public goods games: why human culture and cooperation did not evolve in one step, Benoit Dubreuil argues that around 700,000 years ago, big-game hunting (which is highly rewarding in terms of food, if successful, but is also very dangerous for the hunters, who might easily get gored by the animals they are trying to kill) and life-long monogamy (for the rearing of children whose prolonged infancy and whose large, energy-demanding brains would have made it impossible for their mothers to feed them alone, without a committed husband who would provide for the family) became features of human life. Dubreuil refers to these two activities as “cooperative feeding” and “cooperative breeding,” and describes them as “Paleolithic public good games” (PPGGs). These behaviors would have required a high level of self-control. As Dubreuil puts it in his abstract (bolding mine – VJT):
After that, the reasons for brain expansion seem to vary with the lineage that we’re talking about. In Neandertals, bigger brains evolved because their larger bodies needed sizable brains to control them, and because bigger brains would have assisted with vision, especially in lands with a cold climate and not much sunlight. As a 2013 science article by Wesley Fenlon puts it:
In the line leading to modern humans, on the other hand, bigger brains evolved to assist with social cognition, enabling them to live in larger groups than their Neandertal contemporaries. There is also extensive evidence if mutations in genes regulating the appearance of the face, as well as the development of the voice box, according to a 2017 article in bioRxiv.
So human language may be unique to the line leading to Homo sapiens, after all. But we don’t know yet.
Here’s another article worth having a look at:
Behavioral modernity. There seems to be increasing evidence that behavioral modernity began in the Middle Stone Age, around 300,000 years ago, and kept developing until 40,000 years ago:
http://onlinelibrary.wiley.com/doi/10.1002/evan.10113/epdf?r3_referer=wol&tracking_action=preview_click&show_checkout=1&purchase_referrer=en.wikipedia.org&purchase_site_license=LICENSE_DENIED_NO_CUSTOMER
So it isn’t as if nothing was happening.
People tend to mate with people in the same standard deviation of intelligence. And while there is a strong genetic component to intelligence, it isn’t strong enough to support dynasties of super smart people.
Life span is not particularly relevant to reproductive success. There are families where it is not unusual to die around age 50, but that doesn’t prevent child bearing or fathering.
I do think it’s fascinating that anatomically modern Homo sapiens was present 300,000 years ago — not just 100,000 years earlier than previously thought, but also in north Africa.
As for what people were doing before the rise of “civilization”: presumably they were doing such things as playing, fighting, hunting, gathering, arguing, praying, telling jokes, killing, stealing, asking questions, falling in love, falling out of love, grieving, being happy, being sad, being angry, being afraid, and so on.
They were just being human. That requires culture, but it doesn’t require civilization — which is to say, human cultures do not require agriculture, settlement, hierarchy, division of labor, social classes, organized warfare, metallurgy, slavery, advanced technology, organized religion, or anything else that comes with “civilization”.
Rather than ask, “what were people doing for all that time before civilizations appeared?” we should ask, “why did civilizations appear when they did?” And there are also cases, I believe in South American and African cultures, where a society developed a complex civilization for a few generations and then abandoned it in favor of subsistence farming and hunting/gathering. I don’t have any research on this at hand but can ask around.
For the curious, there’s a new book coming out in August on the origins of civilization: Against the Grain: A Deep History of the Earliest States.
To be sure, there are really interesting questions about which selective pressures drove hominid cognitive evolution. Kim Sterelny has been applying niche construction theory to hominid evolution, and Michael Tomasello has spent his career detailing human-specific mechanisms of cooperation. (Here is a nice article about Tomasello’s work.)
One mechanism that we’ve evolved for cooperating is reasoning, and in particular arguing and justifying (see The Enigma of Reason). There’s growing evidence that the selective pressure to be better at cooperating was crucial to hominid evolution. The next book on this subject I plan to read is The Secret of Our Success, which I just got a few days ago.
What’s important here, I think, is to understand the relationship between arguing and predicting.
I say this because I think Mercier and Sperber are onto something really interesting with their focus on the social nature of reasoning — reasoning is a social psychological mechanism, not an individual one. (This coheres with the philosophical insights coming from the anti-Cartesianism of Hegel and the American pragmatists.)
At the same time, it’s also worth noticing that human beings have astonishingly large brains. In fact, according to Herculano-Houzel, human beings have the largest number of cortical neurons in absolute numbers — far more than animals that have brains with greater cerebral volume, such as elephants and whales. (Elephants have massive cerebella, probably for trunk control.)
Interestingly, this turns out to be because primates in general have small neurons than non-primates, so that primates can pack more neurons and thus more synapses into the same cubic millimeter than a non-primate mammal.
At one level, it just comes down to computational power. Primates have more computational power than non-primates, and we have more computational power than other primates.
But to understand what we’re doing with that computational power, and what it’s good for (and how it earns its keep, metabolically speaking — brains being expensive tissues to build and maintain), we need to understand what cognition is good for.
According to a relatively recent and interesting (though controversial) hypothesis, called the predictive processing model, cognition is good for predicting. On this account, an animal generates a model of its surroundings, and uses that model to make predictions about what is likely to happen. Sensory information conveys prediction errors: how wrong the prediction was. In some cases (but not all) the prediction errors are used to update the model.
If predictive processing is promising as a theory of neurocomputation, and that’s a promising way to think about cognition as such, then a larger brain (more neurons in absolute terms) would be able to construct richer, more detailed, and more complex prediction-generating models. And those models will include models of the social environments (as well the physical environments and the causal relationships between them).
In short, what’s necessary here is to understand cooperation and especially argumentation in predictive processing terms. If it can be shown that cooperation is computationally more challenging than competition because of the complexity of the predictions that have to the generated and revised, but that changes in the Pleistocene savanna circa 2.5 million years ago (earliest evidence of brain increases in Homo) made cooperation an adaptive strategy, then we have a theory about how cooperation drove brain evolution.
But do you think that differential reproductive success between the brights and not-so-brights matters in the context of human evolution? It appears to me that the a slight shift of mean population intelligence toward GED rather than Ivy-League has little bearing on the survival of our species.
Two big problems here, at least. First, survival of the species isn’t relevant to natural selection, which concerns the change in frequencies of alleles within a population. Second, and more importantly, it has not been demonstrated that poor or uneducated people are less intelligent than rich or highly educated ones or if so that any difference has a genetic basis. Can’t talk about selection until we know both that there’s variation in the trait under discussion and that it’s heritable.
I think most people probably don’t have a big problem with the concept of change of frequency of alleles. I think where it gets dicey is the change in alleles.
We don’t seem to have much evidence at all that they ever change for the better. You would think that in all of the history of man, we could at least document a few more cases of alleles getting mutations that have accumulated into a net positive for an organism, rather than just a reshuffling of that which already exists. That’s one problem.
To me, the second problem is, we haven’t a clue where inherent knowledge exists within a genome. Intelligent organisms can’t exist without being born with the knowledge of how to do certain things, like say how to open your mouth and swallow, or how to smell things, or how to look for water…The list of things that each living thing needs to know when it is born is staggering, and yet we have zero evidence for where that knowledge is stored and passed on. If a woodpecker is separated from its parents at birth, and not raised amongst other woodpeckers, it will still learn to use its beak to peck away at a tree, will it not? But a chimpanzee won’t attempt to use its nose to make a hole in a tree, will it?
It should be noted that the African continent is vast and in terms of Evolutionary Anthropology, largely unexplored. It would be foolish to assume to much about what humans did or did not do 300,000 years ago.
vjtorley,
This is not very creationist.
Big brainism has never proved relevant to human smarts. thats old school thought.
First it rejects the soul as the seat of human intellect. Then you make this BRAIN GROWING aw shucks that easy. its a big deal to rewire things.!
Are modern brains sizes to be used to judge smarts? females, i understand, have smaller brains in a smaller head. are you saying this means they are dumber? what about race and the guy over there. His head seems bigger then mine.
is there ACTUAL evidence for brainology growth???
The computer revolution proves small is brilliant.
Brain size is irrelevant and never did humans get bigger brains and thus smarter.
its a humbug. Unless of coarse there is rEAL evidence.
I’m not just saying this because my brainometer is showing my brain a few ounces less then average. i think its broken.
Are you a astronaut?? just not kooky!
the answer is no human history was erased by glaciers.
first there were no glaciers erasing anything.
Secxond the ice ‘age” lasted just a century or two and was in areas unoccupied by people still migrating from Babel.
no cities either for marginal areas with higher water.
Apologies to those who took the trouble to reply to this post. I’ve had some RL to deal with, which is ongoing, but I’ll read and respond as I can.
Size does matter!
I don’t think that and didn’t mean to suggest it. The reason for my post was that the news item was top of the “most read” section on the BBC news website which I thought was pretty impressive with all the political distractions going on
Well, indeed. My surprise that modern humans were around 300,000 years ago rather than 80 – 100,000 years ago just makes me wonder what drove that evolution from Homo erectus in less than a quarter of a million years.
Geoffrey Miller wrote a book, The Mating Mind, where he sets out a case for sexual selection as an element in the evolution of human braininess and language.
vjtorley,
Thanks for the links, Vincent. May take me a while to find time to read them but I will get to it.
I know this. I’ve read Clan of the Cave Bear. 🙂
It’s a problem to which there are many speculative answers but little in the way of evidence, as far as I know at least, as to what was the evolutionary designing force driving brains to get larger. Use of fire, development of cooking, need for organisation and cooperation when hunting large prey and so on, perhaps all these and more.
Not puzzling – it happened. And it happened 200,000 years earlier than previously thought.
Yes, this is the remarkable new fact.
Or Werner Herzog’s movie.
An allele is a theoretical construct. John can change them however he likes.
I think that we need to take on board here the idea of niche construction. Then the question would be, what is the niche that hominids constructed? And I think the most promising answer to that is, obligate cooperative foraging.
One of the big differences between hominids and other primates is that we tend to live in ecosystems where calorie extraction is too time- and energy- intensive for any one individual to perform entirely on his or her own. Chimpanzees, gorillas, bonobos, and orangutans all forage individually. That’s fine if one is a frugivore living in a forest, but not if one is living in a savanna. In savannas, calorie extraction is much more difficult and often requires cognitive resources: one needs to know where nuts are likely to be buried, which berries are toxic, how to make a trap for small animals, and how to cook food in order to increase (quite drastically!) how much energy can be extracted from food in proportion to the energy it takes to digest the food.
My surmise is that obligate cooperative foraging — having to work together to extract calories from the environment — can be understood as the governing motif of hominid evolution, where what drives hominid evolution is “getting better at doing all that stuff“. But then lots of different traits, adaptations, discoveries, and inventions can all contribute in some way or other to that: improved manual dexterity, gestural or vocal displaced reference, figuring out how to cook, making Acheulean tools, etc.
In other words, rather than looking for a smoking gun (or single bullet) we can think about mosaic evolution as being cultural as well as anatomical and physiological, and with that framework in mind, think about how different traits, discoveries, and inventions contributed at different times and in different ways to improving obligate cooperative foraging.
Here’s my theory – tongue in cheek, I just made it up and don’t necessarily buy it – the gap between arrival of large-brain co-operative hominids and the leaving of significant cultural artefacts may be (partly) associated with religion. Hunter-gatherers take the resources of the planet for granted. The gods provide the sustenance from somewhere (or not, if they are feeling mean), and we have to be better at getting hold of that. Beyond that, we are just straws in the wind, nothing you can do but grovel and appease.
The idea of being somewhat in control of our own destiny, particularly through agriculture which seems a prerequisite for the generation of preservable artefacts of ‘civilisation’, may have taken a considerable time to take hold. It’s not obvious, even to intelligent individuals, that it would work, and if one is subject to a fatalist outlook, this may be a further inhibition.
One point the Nature authors make is that previous[ly discovered]* hominid encampments as late as the current find, due to not having Homo fossils associated, have been wrongly attributed to H. neanderthalensis. It puts in doubt who was using fire, cooperatively hunting large prey, knapping flint tools and weapons etc. 300,000 years ago.
ETA *Clarity
Whilst appreciating your nod to the French contribution to science, I concede this point to Dalton’s protégé, Joule!
And how much of this is heritable and what needs to be learned? Maybe the success (in terms of biomass – I make no qualitative assessment) of humans is in escaping from heritability to learning (most importantly, learning to control their/our niche°).
Genetics evolves into memetics!!!
*ducks and runs*
I have to say, I don’t buy it.
As I understand it, the major difference between the spirits and gods worshiped by hunter-gatherers and the “Big Gods” of civilization is that the latter, but not the former, are represented as being interested in human behavior.
There’s some evidence that hunter-gatherer religious practices involving spirits and gods function as cognitive heuristics for retaining and transmitting relevant ecological information, esp information about the history of the ecosystem, in the absence of writing. So the picture you have of hunter-gatherers “groveling and appeasing” the spirits they worship doesn’t seem to fit the anthropology of religion amongst hunter-gathers and indigenous peoples who make a living with subsistence agriculture.
For that matter, agriculture is just as vulnerable to the whims of the gods (i.e. nature) as hunting is — one drought or plague and you’re ruined.
Yes, that was my reading, too.
ETA, I’m referring to Big Gods by Ara Norenzayan
Perhaps both species were. I don’t know. There’s evidence of cooperatively hunting large prey with Homo heidelbergensis, which is considered ancestral to both Homo neanderthalensis and H. sapiens.
You might be interested in this: The Invaders: How Humans and Their Dogs Drove Neanderthals to Extinction.
I think that in hominids, as in other primates, most of what we need to know in order to function in our environments is learned. What distinguishes us is how we learn. For one thing, humans are far better at imitation than other apes. And I think that’s connected to the fact that we do something that apes almost never do: we teach.
For the most part, what happens in apes is that the infant observes the adult doing something and the infant then figures out to achieve the same result. It’s learning, but the adult isn’t teaching. The adult isn’t deliberately constructing an artificial scenario for the purpose of getting the infant to acquire skills necessary for achieving some adult-level goal or task. We do that all the time with our children. Apes don’t. So the evolution of teaching has got to be a really important part of the story of hominid evolution; without teaching, there’s no high-fidelity information transmission across generations that’s necessary for culture.
My experience is that learning is independent from teaching. Being given the chance to observe is a learning opportunity.
ETA pedantry!
Kantian Naturalist,
That is true, but the discovery that one can actually do something positive about one’s access to sustenance is not at odds with that. “Might as well do nothing, since the gods will only fuck us over anyway” was probably not a thought as such!
Bees! Defend the honey!
Ooh, ooh…
Newshound Denyse O’Leary just spots press releases about latest fossil find in Morocco. Ha ha Denyse, you were scooped by TSZ!
Denyse writes:
Speculation is free, Denyse – and fun!
Sure, but hunter-gatherers also need to be able to make complex predictions for near-optimal calorie extraction — seasonal variations in herd movements, which animals are best hunted under which conditions, and so on. The shift to agriculture was more about a shift in which predictions were relevant, not a shift from utter dependence on the whims of the gods to taking matters into our own hands. Let’s not read too much of modernity (the Scientific Revolution and the Enlightenment) into the upper Neolithic!
I wonder if there is any genetic evidence of how long humans have spent selectively breeding plants. I think there is some evidence that links “domestication” of wolves to starting around 80,000 years ago?
ETA Yes there is
Alan:
Others have pointed this out to you already, but it’s worth reiterating: large brains and a capacity for complex communication were of benefit to their possessors long before the advent of civilization, and they remain useful to those who live outside of civilization today.
The need to analyze, to plan, and to navigate social relationships is there whether or not you live in a civilization.
Whilst I don’t disagree that this is a reasonable hypothesis, what evidence do you have that supports it?
Yeah, they’re not bad points, but on the other hand, why didn’t chimps, gorillas, or orangutans go down similar pathways? Of course there were other hominins that did, but then some of them seemed not to undergo much evolutionary increase in cognition before going extinct.
It’s not that hard to see how brains might be of benefit to hunter-gatherers, but it’s about as easy to see how they might not be of any especially great value (and big brains have significant costs, too).
As for why agriculture might begin when it did, it seems to have happened not long after mega-fauna went extinct, and probably after even smaller (but still considerable) prey quit being fairly accessible as migratory herds. There seemed to be a fairly dense (for capacity) human population that wasn’t being well-fed. Agriculture wasn’t nutritionally great, but at least it could provide calories.
Glen Davidson
GlenDavidson,
Hindsight is a wonderful attribute of large brains, too!
Again, a reasonable assumption. But the Pleistocene extinction(s) appear to be much later than the emergence of modern humans.