Originally, I planned two major posts summing up in detail the history of our species. Unfortunately, it turned into a big slog. I left the project a few years back, unfinished, and it would require several months of dogged research now. My life is too unsettled at the moment to allow that. But at the same time, it is impossible to sally forth into deeper explorations of early agriculture and social complexities without at least sketching an outline of our “true history” — true, in this case, meaning a clear focus on the full span of our time as the species H. sapiens, not more, and not less.
Somebody ought to write a beautiful coffee table book, showing vividly the utter awesomeness of the Paleolithic world where megafauna roamed free, humans were just one species among many, and elephants were the “lords of creation” and doing an excellent job of it! An eye-opening and radicalizing bit of time travel it has been for me. So, here is a quickie, to share what I’ve discovered. Caveat: this is my own synthesis; others may disagree with some of the details; there is little in deep history that is not contested…
- Curtain opens at about 200,000 years ago, as the world is heading into another ice age. Sapiens in lower Africa; Neanderthals in Europe and northern Asia, and several other descendants of erectus in southeast Asia. Humans talk, use fire, hunt, cook, make rafts, fire-hardened spears and simple stone tools.
- Sapiens love to inhabit caves near rivers or the ocean; a number of them have been excavated and described in southern parts of Africa. Humans thrive in small egalitarian bands of 20 to 40 people; very local trade exists between bands.
- Ice age comes to an end around 130,000 years ago, and for a while it’s quite hot. The vast majority of human artifacts from this interglacial come from the Neanderthals. Artifacts get more interesting. Humans love ochre and other pretty rocks. They invent fancy glue, make composite tools (wood and bone), fish hooks, and bury their dead.
- The climate cools again toward another ice age. The massive Toba eruption (c. 71,000 ya) causes a 6 year winter and sapiens barely escape extinction.
- About 60,000 years ago, descendants of erectus float or sail to Australia. And sapiens humans start moving out of Africa.
- 50,000 years ago… many more tools, much improved; something is happening to sapiens brain, enabling a cultural shift into greater complexity of both language and artifacts. Art becomes common. Flutes. Sewn clothing. Conscience emerges.
- Sapiens are coexisting and occasionally mating with Neanderthals in Europe, until 25,000 years ago. Pockets of humans survive the ice age at higher latitudes in refugia where megafauna is particularly plentiful. In these spots, culture flowers, tools are finessed, cave walls are painted and rituals performed. First child-dog bond in evidence some 33,000 years ago. America discovered and begins to be settled.
- R.I.P. our Neanderthal cousins
- Ice age maximum reached at 20,000 years ago. The cold drought kills perhaps 90% of humans in Australia. Abrupt warming fosters flourishing sapiens cultures in Europe and the near East; horses and reindeer actively cared for and seeds sown. Pigs domesticated by Anatolian foragers around 13,000 ya. Inequalities begin to emerge in some bands. Resurgence of ice during the Younger Dryas period (13,300 ya to 11,800 ya). The construction of monumental Göbekli Tepe begins soon after Younger Dryas ends.
- 10,000 years ago, a warm moist world of plenty; in a few areas, humans settle down and build more permanent shelters and walls; gathering and cultivation of plants and animals intensifies, populations grow. Some human groups transition from egalitarian to Big Man (transegalitarian) social structures. First towns (and regional civilizations) emerge in the Near East; people flock there voluntarily; peace and relative equality reigns. First truly agricultural villages appear around 7,000 years ago, and regional environmental collapses resulting from human activity are in evidence toward the end of the Neolithic.
- 6,000 years ago, first transitions to advanced metallurgy, bronze weapons, city-states, and war. The very first incarnation of “this civilization” emerges in Sumer. Women are actively marginalized, social stratification increases, and health and longevity deteriorate for those lower on the pecking order. Non-civilized tribes begin to be pushed out. Wholesale slaughter of regional megafauna emerges as a status sport. Amazing art and devious cruelty advance apace.
- First brutal empires (Akkadia, Babylonia and Assyria) emerge about 4,000 years ago. War and standing armies assume a menacing presence in a few places. But most areas of the globe continue to be settled by egalitarian or transegalitarian tribes. Sahara forms (without human help). Peaceful and relatively egalitarian civilizations emerge in Peru and Amazonia. Terra preta invented.
- By 2,000 years ago, many societies continue to complexify; “great religions” emerge and manage to modify somewhat the brutality of the age of empires. Civilized humans preen as rational beings and lords of creation and begin to take over everything they can reach. Writing spreads. So do plagues. Mathematics, science and frequent technological breakthroughs start to make a difference in the human condition. Oceania settled by intrepid explorers in outrigger canoes.
- 400 years ago, about a third of the planet is still out of the control of states and empires; semi-nomadic hunter-gatherers, pastoralists, slash-and-burn farmers, and horticulturalists continue to thrive. “Civilized” agriculture grows more productive.
- 250 years ago, industrial civilization’s “Satanic mills” move into “mow down the living planet” mode, encourage out of control human reproduction, and filthify everything. Last autonomous tribes on the way out. Planet increasingly devastated. At the same time, many humans reap unprecedented benefits — including longer life-spans — from advancing understandings of science, medicine and technology. Ideology of progress and sharing the pie quells unrest. Then, within the space of a few decades, this civilization begins to show serious cracks. Elites keep their heads firmly wedged, er, in sand. Humans are, overall, increasingly well-connected, educated, stumped by often self-inflicted crises, and suffering from multiple addictions. Will they survive?
Leaving Babylon 
November 27, 2014 at 1:09 pm
This is why anthropology should be taught in high school. When I was in grad school at Portland State, one of my fellow students had actually had it in high school in Pendleton, Oregon. (I was jealous.) The US government has understood this since World War II when anthropologists were recruited into the OSS (which later became the CIA). Recently the US Army started using anthropologists to train soldiers so they could become more culturally sensitive, but – as usual – the Army screwed it up and it quickly became a program to better exploit cultural sensitivities of the indigenous Afghans and Iraqis.
I suggest you delve deeper into what culture is. You only mention it once in an offhand manner. This is the supreme paradigm of anthropology and IMHO the supreme paradigm of the social sciences. Paleoanthropology, archaeology, biological anthropology, medical anthropology – in short all the subfields based in natural science methodology – all orient towards this paradigm.
Glad to see you are taking the long view.
November 27, 2014 at 2:23 pm
Walter, I want to delve deeper into “culture” but find it slippery. Can you point me in a direction?
November 27, 2014 at 3:42 pm
Yes, it is slippery. For starters, re-read Chapter 1 of my first book. Then try this: http://www.amazon.com/Ethnographers-Magic-Essays-History-Anthropology/dp/0299134148 You can get a used copy for $3.28.
George Stocking was the go-to guy in the history of anthropology when I was in grad school. You might find this book relevant for a whole bunch of reasons. Also, get yourself a basic Anthropology 101 text at a used bookstore. I like Haviland, who I used when I taught Anth 101. Check this out:
http://www.livinganthropologically.com/haviland-anthropology/
Careful. The study of culture will consume your life. Toni and I talk about it every day. (She is a social worker but got her B.A. in anthropology/psychology.)
November 27, 2014 at 6:12 pm
When I was studying this heavily, I liked Brian Fagan’s People of the Earth. Then it got heavily revised and restructured a few years back, and I did not like it as well. I would recommend the earlier edition. What I was missing in the books I saw was more of a discussion how culture is formed… my sense of it is that some people are quite adept at playing the culture-shaping game, and not necessarily openly…
November 28, 2014 at 11:30 am
The evidence I know supports most of what you have sketched. My only question concerns the evolution of speech and language which you date at 200,000 ya. I think it is much later–after 100,000 ya, and related to the emergence of the mind from the brain that you mention, as well as changes in the mouth and throat.
November 28, 2014 at 2:13 pm
Welcome, Jim. Good to hear the feedback. I read that the first remnants of a hyoid bone date from about 250,000 ya… now this would not be sapiens, but still… so I am assuming that they used language. It would have been of course much simpler than the complexities and syntax that emerge around 50,000. In any case, it’s conjecture.
What sort of evidence do you have for the later date?
November 28, 2014 at 2:38 pm
The go-to guy here is Philip Lieberman. Here is a quote from a 2007 article in Current Anthropology. “Fully modern speech anatomy is not evident in the fossil record until the Upper Paleolithic, about 50,000 years ago.” You can download the PDF file here:
Click to access Lieberman%20P.%202007.%20The%20evolution%20of%20human%20speech,%20Its%20anatom.pdf
Of course the defining term here is “full modern.” It is likely there were some speech patterns in Homo erectus/ergaster as well as Homo neandertalensis. What the default thinking used to be is that H. erectus could similarly to a 2-year-old and Neandertals similiarly to a 3-year-old modern human. I don’t know what the current thinking is on “incomplete” speech acquisition. A person should also remember that 3-year-olds only have about 80% of modern grammar and that last 20% takes about a dozen more years. You can approximate that by focusing on “embedded grammar” being complete by about the age of 15. You should also look into Chomsky.
You have opened a gigantic can of worms here.
November 28, 2014 at 2:39 pm
Correction: What the default thinking used to be is that H. erectus could speak similarly to a 2-year-old and Neandertals similarly to a 3-year-old modern human.
Sorry.
November 28, 2014 at 3:28 pm
Looks like Lieberman posits that language began evolving from the time we (pre-humans) began to walk and run. That means several million years back — 4? So that would mean that by the time sapiens emerges, it has functional speech, even though full-fledged modern speech does not appear till about 50,000. Does that make sense?
November 28, 2014 at 5:29 pm
1) Don’t confuse language with speech. Humans have speech, chimpanzees that use AMESLAN have language.
2) Looking at the development of the “dropped” larynx as humans develop may be more fruitful than a “predisposition” to speech in the human lineage. In other words, as humans evolved into new forms that we call “species,” they had a change in the expression of the the genes for language.
3) On the other hand, it could have a great deal to do with the tongue.
“In short, in itself a low larynx is not an indicator of potential phonetic ability. Claims such as Fitch’s (2000b) that the human vocal tract evolved to produce lower formant frequencies by laryngeal descent (providing a false vocal impression of a larger body) cannot account for the evolution of the species-specific human vocal tract, which involves the descent of the tongue into the pharynx.”
4) Your next line of evidence is exactly what the FOXP2 gene does.
“The evolutionary significance of the regulatory FOXP2 gene, which has erroneously been identified as a “language gene,” rests in the fact that it governs the embryonic development of the basal ganglia and other subcortical elements of these neural circuits (see Lieberman (2000, 2002, 2006a and the studies noted below).”
5) Bottom line: Yes hominids are predisposed for language (e.g. chimps and gorillas can learn AMESLAN because they have the mental equipment to do so) but only the hominins have the necessary vocal tract development for speech. Hominins include the Australopithecines. Of the hominins, the necessary predisposition was there but not the super brain power. As one of my profs used to say, “Chimps are large-brained hominids. Humans are grotesquely-enlarged-brained hominids.” There is even a quantum difference in the encephalization quotients (EQ) of Australopithecines and modern humans.
6) big brains—->language predisposition—->dropped larynx&tonge——>huge brains———>speech
7) It is likely Neandertals were outcompeted because the modern humans who invaded their territory had better speech, more supple fingers, and larger groups.
November 28, 2014 at 6:27 pm
What about song? A simpler throat could possibly emit sustained and less shapely vocal sounds to indicate 1) food source, 2) predator types, 3) directional calls, 4) baby babble, 5) mating calls, 6) game flushing and coordinated attacks, 7) non-threatening companion intent, 8) aggression, 9) fear, submission, 10) grief, 11) joy, ecstasy
November 28, 2014 at 8:20 pm
This topic is endlessly fascinating, considering how it defines who we are and how we got to this point in history. Biological development is no doubt an ingredient, but from about 15,000 years ago, cultural development far outstripped the speed of biological/evolutionary development, and accordingly, transformed the face of the world.
However, culture is a moving target and far more open to disagreement in how the story of civilization is told. Further, considering the diverse points of contention among those paying attention and the complete disregard paid by the general public, I don’t see how, fundamental as it is, cultural anthropology rises above purely academic interest. I pursue it, too, but I can’t shake the sense that whatever understandings I come to are largely irrelevant.
November 29, 2014 at 8:16 am
Brutus, funny, I find it hugely illuminating, and the reason I have pursued it is, I think it holds the answers to “what the heck happened?” — without which is hard to think clearly about what might be done to get us out of here. But at the same time, as you say, it’s so fascinating for its own sake!
Gkb, exactly. Walter, I am not so much interested in the finer points of language/speech anthro/archeology etc as I am in getting a sense of what we may have been like 200,000 ya. If we moved into full modern language/speech 50,000 ya, is it likely that we had none 200,000 ya? I hardly think it was grunts then. I am assuming that — while at 200K language/speech was much simpler, and perhaps used gestures much more, the way Jean Auel imagines the Neanderthals talking — still it was likely a very functional way to communicate, and already feeding human culture. I guess I am fishing here for an argument why this picture would have been unlikely. Without it, I am sticking with it! 🙂
Oh and Lieberman makes the good point that unless there was a major payoff in terms of communication advantage, the greater risk of choking that accompanied the evolution of our throat would not have been worth it.
November 29, 2014 at 9:54 am
If I were comfortable with (radical) reductionism, I would conclude that it’s our biology that got us to here (in time). Duh! But clearly it’s more complicated than that, and further, I wouldn’t collapse psychology and culture into biology as mere functions. That said, I have been reading and blogging on Iain McGilchrist’s 2010 book The Master and His Emissary. His take on the big question (“how did we get to here?”) is that it’s essentially an artifact of the hemispheric structure of the brain, where the left hemisphere (the emissary) has usurped power from the right (the master). He brings a multidisciplinary approach to the endeavor and is very convincing.
http://www.iainmcgilchrist.com/
My only criticism (and frustration) has to do with disposing of free will, and with it, responsibility. Alternatives such as the thermodynamic and genetic explanations do the same by saying we’re (just) meat robots obeying our programming and that the destruction of the world, while not an object of that programming, is nonetheless a result of it. Identifying power laws that let us off the hook and allow us to continue what we’re doing bother me because they hollow out human experience on earth. But there are still seeds of truth behind those versions.
November 29, 2014 at 12:25 pm
Well, that’s it, isn’t it? People like him “dispose of free will” but I betcha they behave in real life as though they do have choices, and with them, responsibility. I think semi-determinism is the commonsense position…
After all, doesn’t the universe show randomness and novelty? I think modern physics and complexity theory would say yes. (?)
November 29, 2014 at 5:00 pm
The most parsimonious argument is that modern humans 200,000 years ago were like us. They had the requisite morphology and so likely had very complicated languages like we do today.
However, since language is the carrier of culture, their different languages argue for different ways of thinking. Since we are constantly evolving, there might be other differences too. Third, since they ate different foods that were cleaner than the foods we eat, there would likely be differences in their thought patterns there too.
Bottom line: They were probably smarter and cooler than we are.
November 29, 2014 at 5:06 pm
“They were probably smarter and cooler than we are.”
Hah. Ya just made my day, Walter.
December 1, 2014 at 6:15 am
The oversized brain of humans was necessary to escape the big cats (lions, tigers), it is a result of evolutionary selection.
A bigger brain (especially a larger cortical region) allows humans to run faster and in a more upright posture, to plan in advance to avoid attack, and to use tools to ward off attackers. These abilities hinge as well on other physical adaptations such as longer legs, nimble fingers, and a straight spine; however, the physical changes sans a powerful coordinating brain would have failed to accomplish the for survival necessary improvements.
A larger brain, resulting in a larger head, made childbirth more difficult. Humans are born with an underdeveloped brain (in a head which is still large enough to make childbirth more painful than for other mammals), therefore children have to be nurtured and cared for an extended period.
Human brains continue to grow after birth, which means increased brain plasticity. Nurturing, education, the social and cultural environment influence the growing brain and form individual characteristics of a person.
The childhood peak in brain glucose uptake by the human brain, which involves over-proliferation of energetically costly dendritic arbors and synapses before activity-dependent pruning in puberty, explains the for mammals unusual slow childhood growth.
The formative influences of family and education mean, that in addition to genetics and epigenetic social and cultural traditions define the home sapiens.
Scientific findings about brain sizes suggest that intellectual capacity diminished in the last 10,000 years and only recently rebounded. (Just imagine how intelligent our early ancestors must have been to split stones without metal tools or lit fire without matches or a lighter.)
Language, self-awareness, human consciousness are a result of evolutionary selection as well, because they allowed to coordinate task distribution in a group, develop sophisticated tools and practices, and live in complex social organizations.
Language as a unique trait of humans is overrated. Bird songs, wale songs, and acoustic or visual expressions of many other species are complex and allow warning, courting, soliciting, display of emotions, and other essential communication. Chomsky’s theories can be explained by his speciesism. Human speech is unique, but so is the sign language and the low frequency rumbles of elephants.
We consciously think in words, because they can be easily compared, correlated, rearranged via our very capable working memory (central executive) in the prefrontal cortex.
But intuition, creativity, imagination, phantasy, all based on pattern recognition, are still the more potent features of the human brain. If we wouldn’t use words, we would use symbols, pictures, gestures. The complexity and sophistication of animal and plant communication is poorly understood, we would maybe astonished about its profoundness if we ever made the effort to learn about it.
Brain plasticity means that every existing instincts or imprinting can be overwritten by a conscious effort. Human ability to change our personality is our best chance of surviving. The change must focus on nurturing, family environment, and education, but include all ages and be synchronized with paradigm shifts in culture, economy, and politics.
A tough mission, which will only be accomplished after pandemics and wars have reduced human population and advanced techniques of dissimulation, isolation, and defense made the predatory destruction of newly formed sustainable lifestyle communities by warrior societies impossible.
Anti-globalization, self-sufficiency, containment and isolation of the warrior societies are crucial steps to make new communities viable.
At Brutus: What is the fascination of free will? Where should a freed will switch be inserted in our decision process? If our decisions were random and not based on motives, experience, reasoning, there would be chaos, there would be no society. If a person doesn’t act rationally, we consider her/him to be crazy, we don’t just shrug and accept her/his “free will.”
December 1, 2014 at 1:38 pm
to Mato48:
It appears from the way you frame the question that you misunderstand the concept of free will. Simply put, free will is the ability to determine for oneself one’s actions. Materialists often assert that our response patterns are not our own but are instead simply a function genetic programming, as though we are being buffeted around kinetically by exterior forces. If that is true, then personal agency is an illusion and we are all off the hook for good and bad faith in the way we act in the world. It also reduces the totality of reality to a meaningless, deterministic whorl of atomistic action-reaction.
Maybe that’s all true from a certain perspective, but even without resorting to religious explanations, I daresay you will have a hard time convincing anyone that his or her consciousness, identity, self, and/or spirit doesn’t actually exist. Daniel Dennett calls consciousness a “benign user illusion,” an interface between internal experience and outer reality. But considering how central consciousness is to who we are in the world, as Leavergirl points out, no one acts as though he doesn’t have choices and influence, however miniscule, over outcomes.
Free will is not, as you appear to believe, random and chaotic. We are constrained by lots of things, but we still have plenty of room to maneuver meaningfully.
December 2, 2014 at 5:05 am
To Brutus:
I try to be as short as possible, if necessary I can go into details in a following reply.
One cannot argue about metaphysical assumptions, because they are beliefs and not based on science. One cannot argue about religion, ideologies, superstition. One can argue to some degree about the logical / grammatical construction of the sentences, which describe a particular philosophy and the associated ethical framework, but in the end the choice of ones philosophy is an individual choice based on education, experience, and personal preferences.
Therefore a philosophical discussion can be not more than either a bickering about words or a playful exercise in semantics, grammar, and logic.
You write, that I allegedly misunderstand the concept of Free Will. If Free Will is a concept, that means it can be
1. a general notion or idea.
2. an idea of something formed by mentally combining all its characteristics or particulars; a construct.
3. a directly conceived or intuited object of thought.
If you want to avoid having Free Will classified as a notion, an assumption, a theory, an axiom, a construct of our minds, you should avoid the word concept. Or do you agree with my view, that Free Will is a concept, which people have developed to explain their complicated and perplexing inner world and the evenly complicated and perplexing world around them?
From a deterministic point of view we are a biological system (or more correct an assembly of various interconnected biological systems), stabilized by countless feedback loops. As that we are a part of the eternal (eternal at least for us) flow of energy (or matter) plus included turbulences, of physical processes on the planet earth which can sufficiently be explained with the second law of thermodynamics, with chaos theory, probability theory, network / graph theory, and related sections of higher mathematics. Quantum mechanics may be useful too.
All these scientific theories are crude abbreviations, because our brain only contains 86 billion neurons and the limits of our senses and our cognition doesn’t allow us to perceive or understand reality in all its complexity (we couldn’t even get the Higgs boson right).
The acknowledgement of our cognitive and intellectual limits lead to the assumption, that only one’s own mind is sure to exist, an epistemological position commonly known as solipsism. In other words: Anything outside one’s own consciousness is unsure; the external world and other minds cannot be proven beyond doubt and they might not even exist outside our consciousness.
Solipsism is an important ingredient of many philosophies, including rationalism (cogito, ergo sum), idealism, nihilism, materialism, and positivism. So it is no big deal to endorse this view.
The assumption that Free Will is more than an idea in our mind, that it is maybe even one of the universal laws that are regulating the universe, is from a solipsistic point of view adventurous, if not audacious.
Are we really that relevant in the wide spaces of the universe?
Free Will is a concept, which makes us feel very important, eminent, outstanding, which elevates us above the fray of other living things. We are not “a meaningless, deterministic whorl of atomistic action-reaction” (great phrase, thank you), not simply a result of genetics, epigenetics, nurturing, education, experiences, and social environment.
Thanks to Free Will we are not simply part of a movement, an aggregation of organic matter, a tiny grain in the great scheme of things, we are more than that, we are special.
Do animals and plants have Free Will? No, I don’t accuse you of specicism.
I agree with you that the words consciousness, identity, self, spirit (you forgot qualia and soul) exist. But as humans until now were not able to detect them in peer-reviewed scientific experiments, they remain words.
They remain words and concepts similar to Free Will.
You write: “We are constrained by lots of things.” Please explain. If we are constraint, we are not free to choose — at least according to my personal logic. If your logic is different, we cannot argue anyway.
Throughout my life I didn’t get the impression that I had any choice. I muddled through and acted to the best of my knowledge. Sometimes I made bad choices out of stupidity, sometimes I was mired in illusions and unrealistic expectations. I often was irritated, mislead by false assumptions, dogmatism, aggressions. Fortunately I discarded the ballast of religion, ideology, philosophy already at the age of 16, that helped a little bit. I made the best choices when I had a clear head, only lead by common sense, reason, life experience, and scientific knowledge.
Fortunately I never had to bother with Free Will, to make the right choice without Free Will was already difficult enough!
December 2, 2014 at 3:02 pm
So I’m being schooled on solipsism and semantics, eh? I will admit that in the brief paragraphs I’ve written, it would be impossible for a reader to ascertain what I know, but I am not an ingénue on these matters. Frankly, I can’t track the points being made through the faulty writing, which I presume originates from someone for whom English is not his or her first language. Let me add just one thing:
mato48 quoted me as saying “We are constrained by lots of things,” omitting the remainder “but we still have plenty of room to maneuver meaningfully,” then proceeded to argue as though I had made a statement of absolutes. Clearly I adhere to no such absolutism, and I consider it bad faith (trolling, if you will) to enter into this style of argument, so I won’t have anything further to offer.
December 3, 2014 at 11:58 am
mato48 – “The oversized brain of humans was necessary to escape the big cats (lions, tigers), it is a result of evolutionary selection.”
Be careful of the “adaptationist programme,” as Gould and Lewontin put it. Mutations don’t happen because they are needed. They happen because they just happen. [Sidebar: Randomness is the sticking point for the Vatican, by the way, as well as the jumping-off point for the “intelligent design” folks. If you cannot accept randomness, you really don’t understand evolution by natural selection.] Here is a PDF for you: http://faculty.washington.edu/lynnhank/GouldLewontin.pdf
December 3, 2014 at 12:21 pm
For cultural anthropology, I like Marvin Harris – an early proponent of cultural materialism, the notion that the material conditions of a society largely influence its culture. For general understanding of homo sap, I think Ernest Becker, “The Denial of Death,” is essential. And Paul Shepard, “Coming Home to the Pleistocene,” was a revelation.
December 4, 2014 at 11:41 am
To Walter Haugen:
Your comment is certainly valid, as mutations happen randomly all the time. I read Gould’s paper, it is fortunately only 19 pages, and I sorted it into the folder with 6 books from Gould that I fetched a long time ago and which I unfortunately was not able to read because of time constraints. Gould is a great writer and I accept anything written in the addressed paper.
The cited sentence from my comment is simplifying, I wanted to keep the comment short. It also does not correctly reflect my view because I personally suspect that our adept and flexible fingers were the eminent trait which gave us the edge over competing species and brain capacity was a subsequent development.
Being not a scientist I go with the crowd and have settled on modern evolutionary synthesis, which is at the moment the prevalent theory. Genetic drift certainly plays a role, allometry plays a role. The role of feedback loops still is underrated though that seems to change.
Click to access Feedback_Theory_and_Darwinian_Evolution.pdf
Click to access 1003.1231v1.pdf
http://cires.colorado.edu/~doug/extinct/
Negative feedback loops are the basis of nearly all stable systems of nature. Random variation of complex dynamic systems (ecosystems, living organisms, the human brain, social and cultural networks) evolve all the time. The unstable ones decay and disappear, the stable ones prevail. The stable variations are stable because of accidentally emerged negative feedback regulation which prevents them from runaway growth and drastic changes which render the system dysfunctional.
This is the principle of self organizing networks and the principle of dynamic natural systems as well. Evolution by selection (better elimination) is only one part, the other part is self-regulation via feedback.
One example:
A nasty weed overgrows the garden and suffocates all other plants. In a healthy biological system this weed will soon attract animals (caterpillars, plant lice, beetles) which will decimate it. The herbivores will attract predatory carnivores who will keep their populations from exploding. Every now and then one of the involved species will be eliminated because it either has unwisely exterminated the species which was its food source or it has itself been eliminated by another organism higher up in the food chain. The system as a whole though will not break down, as other weeds, other plant eaters, other predators will quickly take the place of the eliminated species. The eliminated species will also rebound occasionally because some individuals could escape the onslaught in a hidden corner of the garden.
This is an oscillating system where species constantly rotate. The controlling feedback loops are the predators on one hand and the occasional decline of the food source on the other hand.
In a biological diverse system with many competing species this cycle will go on indefinitely.
Another example:
The ash tree in Europe is threatened by a specialized fungus (ash dieback), more than 60 percent of trees are infected. The disease cannot be cured and ash trees will disappear. But without trees the fungus will also disappear and if in some remote area, maybe in the far north where biting cold disables the fungus a few ash trees survive they may over many hundred of years repopulate Europe. Another possibility is that some trees will become resistant against the fungus because of slight mutations and that these trees over time replace the old populations. The fungus of course could also mutate but it would not be able to spread easily because the ash trees would be only few in between other trees species.
I don’t address Goulds “Punctiated Equilibrium” to keep the comment short.