How did we come to be us?

[peter]

What I am intersted in here is the things that had to come together and the order and pressures that pushed our development in the direction that resulted in, well - us.

Between 3 and 4 million years ago Lucy (Australopithecus afarensis) is wandering around the plains of Kenya. She is hominid, ie she walks upright, but she isn't human. By 2.5 million years something has happened. Homo habilis is around and he is a tool maker (as opposed to a tool user) and may well have begun to show the rudiments of speech development. For this to happen (ie speech development) two things must occur - complicated changes both within the brain and the construction of the jaw/toung/larynx. I assume the brains capacity for extempory thought, for thinking on matters not directly pertaining to the self, for thought on abstract subjects (Why am I here, is there a God etc) and for consideration of the not immediate future, is a development subsequent to the development of speech of suficcient complexity to convey such ideas. It is difficult to imagine that very complex ideas can easily be formulated in 'picture form' in the brain without a framework of words and phrases with which to conceptualise the meanings.

So it seems to me that the development of speech had to precede the development of ideas and had to be the driving force behind the (on this idea) subsequent development of the brain into the organ capable of the range of complex mental activities we now posess.

Does this concur with the current view in anthropology or do the experts see a different keystone in the development of 'being human'. Also, if the evolutionary pressure was from development of ever more complex communication sounds pressing for ever more development of the jaw/larynx to make those sounds and ever more complex areas of the brain to contrive and interpret those sounds - why didn't other species do it when they faced the same pressures. Lastly what have I missed out on the path to becoming human. I've mentioned a path of increased need for communication resulting in brain development; upright gait freeing the hands and the bigger brain kicking in here for tool development. Further brain development brought about by the 'new' brain being almost acidentally capable of more types of thought once the power of increased brain size was coupled with the capability of conceptualising complex ideas. Anything else?

[I'm Murrin]

I expect simultaneous, complementary development will have been the reality, rather than any one thing directly preceding another.

Speech for coordination with others, abstract thought coming from the need to be able to think ahead and innovate (the earliest abstract thought, I expect, is that which says "if I do this now, then something else might happen later"). Different but with uses that fed into one another.

We know that undeveloped animals can communicate (some have the rudiments of what could become language), we see apes and monkeys with the earliest levels of tool use (going as far as sharpening sticks), we know some are capable of abstract thought to a small degree. Hmm. I'd say if anything comes before all of these things, it is the ability to teach and learn behaviour. Once you have that, these other things can develop independantly and for different reasons.

Obviously I cannot speak for expert opinion.

[Hashi Lebwohl]

We need to dovetail this with the research that appears to show that there was a genetic bottleneck about 75,000 years ago, so that most modern human descended from only a very narrow family of ancestors. Even if that research if off by a factor of 10, that still gets us back to 750,000 years ago which isn't anywhere near 3 or 4 million.

What happened to all our competitors? I suspect disease or parasite or some other accident that was simply fortunate for us. In short, we are simply the lucky ones. As I'm Murrin notes, there were probably simultaneous lines but unfortunately for them they didn't make it.

What would be odd would be if we were somehow the result of too much inbreeding. A random genetic twist because of insufficient variety results in a more complex brain structure, those children are able to outperform their parents, outbreed them, then pass along their traits. *shrug* No evidence at all for this but it is interesting conjecture.

[Avatar]

'Most recent common ancestor' of all living humans surprisingly recent

New Haven, Conn. -- In this week's issue of Nature, a Yale mathematician presents models showing that the most recent person who was a direct ancestor of all humans currently alive may have lived just a few thousand years ago.

"While we may not all be 'brothers,' the models suggest we are all hundredth cousins or so," said Joseph T. Chang, professor in the Department of Statistics at Yale University and senior author on the paper.

Chang established the basis of this research in a previous publication with an intentionally simplified model that ignored such complexities as geography and migration. Those precise mathematical results showed that in a world obeying the simplified assumptions, the most recent common ancestor would have lived less than 1,000 years ago. He also introduced the "identical ancestors point," the most recent time -- less than 2,000 years ago in the simplified model -- when each person was an ancestor to all or ancestor to none of the people alive today.

The current paper presents more realistic mathematical and computer models. It incorporates factors such as socially driven mating, physical barriers of geography and migration, and recorded historical events. Although such complexities make pure mathematical analysis difficult, it was possible to integrate them into an elaborate computer simulation model. The computer repeatedly simulated history under varying assumptions, tracking the lives, movements, and reproduction of all people who lived within the last 20,000 years.

These more realistic models estimate that the most recent common ancestor of mankind lived as recently as about 3,000 years ago, and the identical ancestors point was as recent as several thousand years ago. The paper suggests, "No matter the languages we speak or the color of our skin, we share ancestors who planted rice on the banks of the Yangtze, who first domesticated horses on the steppes of the Ukraine, who hunted giant sloths in the forests of North and South America, and who labored to build the Great Pyramid of Khufu."

The results can also work backwards, into the future. According to Chang, "Within two thousand years, it is likely that everyone on earth will be descended from most of us."

###

Other authors are Douglas L.T. Rhode of the Massachusetts Institute of Technology and Steve Olson of Bethesda, MD. The National Institutes of Health supported this research.

Citation: Nature 431: (September 30, 2004). For solicited commentary on this paper, see News & Views and supplementary material in the same issue.

--A

[peter]

I would imagine that 'the ice age' (not sure which one - the last one only ended ten or so thousand years ago) would have played a major part in the extinction of our closest 'rival' human species. Clearly genetics is beginning to play an ever greater role in our understanding of human development and it may indeed be the case as Hashi touches on, that at some point a totally random event occurs that results in a significant devlopment. Indeed some anthropologists theorise a 'great leap forward' some 50,000 years ago - a step-change (quote) "in human evolution, sparked by genetic changes that resulted in a 're-wiring' of the human brain".[See Jared Diamond; The rise and Fall of the Third Chimpanzee]. This view though not well supported by the scientific community, rests on the sudden appearence of a much greate variey of stone and bone tools, greater 'technical' innovation and the sudden flowering of artistic endevours seen in Europe and elsewhere.

I wonder to what extent the business of evolution bringing about a devlopment to deal with one need, and suddenly finding that the development can do something else much more significant elsewhere, has opperated in our development - particularly in the case of the brain. (nb Evolutionists have a name for this phenomena but I can't remember what it is.

Another aspect of 'becoming us' that bears consideration is 'have we always actually been us. ie Was the human 'conscious' always what it is today even in those early 'behaviorally modern humans' (say of 30,000 years ago) or has the concious changed; if so since when - have I the same concious as an ancient egyptian, a medieval person, a victorian even (my next door neighbour!). I have read a couple of books that engaged this subject, most notably "The Marriage of Cadmus and Harmony" by Roberto Callaso, but could not understand a word of the ideas they attempted to convey wrapped as they were in allegory and metaphor. And if I have a different 'conscious' to my ancesters how did they see the world as being qualitatively different to me. Big questions I know - but interesting ones.

[Hashi Lebwohl]

Avatar, that research seems to contradict the statistical analysis done on mitochondrial DNA that puts our bottleneck, and thus common ancestors, at about 75,000 years ago. I find it difficult to believe that our common ancestors were only 3,000 to 5,000 years ago--that is far too close.

Yes, peter, we have pretty much always been us. You do have the same consciousness as people 10,000 years ago did but you have the benefit of 10,000 years of people studying philosophy and theology (not to mention the hard sciences) so you have a lot more information available to you than they did. You don't believe that trees, rocks, clouds, and the wind have spirit like you do--you are not an animist--so naturally you view the world differently. Still....your brain is wired the same as the people in the marketplaces of Catal Huyuk.

[I'm Murrin]

Av's quoted article there is not so much about common evolutionary ancestors, but about communication and interbreeding among humans worldwide. It's just that a population of thousands growing to a population of billions means everyone alive now is related to everyone who was alive then.

[Hashi Lebwohl]

Oh, that. Yes, I have seen that kind of information before. Even if we presume that each generation is a flat 25 years (which we know is not accurate because in centuries past a generation was only 20 years) and we begin counting backwards then at my birth I had 2 parents, 25 years before that I had 4 grandparents, 25 years before that 8 great-grandparents, etc. until we go back 40 iterations to find that I had 1 trillion ancestors at that time; this is more human begins than have been alive since the planet coalesced into its present shape. 40 iterations of 25 years is only 1,000 years so yes--I am related to you. All of you. Five times over.

This kind of research should dispel racism because there aren't different races of humans, only different window dressing.

[Avatar]

Definitely agree with that last.

Anyway, yes, as Murrin suggests, it's not about the specific person we're all descended from, it's about recent common ancestors. Everybody on earth is related.

Even that bottleneck you're talking about, (IIRC, it was when the entire world population dropped below 10,000 or something) wasn't the source of our inter-relation. I seem to recall there's a single common matrilineal ancestor well before that.

--A

[I'm Murrin]

We keep finding new evidence of small groups of slightly different humans in different parts of the world. I think the common thought now is that there was a first wave of humans that left Africa and spread into Europe and Asia, began to diversify in those regions, and then a second wave came out of Africa spreading across the same areas that interbred with the descendants of the first wave.

[TheFallen]

Oh, that. Yes, I have seen that kind of information before. Even if we presume that each generation is a flat 25 years (which we know is not accurate because in centuries past a generation was only 20 years) and we begin counting backwards then at my birth I had 2 parents, 25 years before that I had 4 grandparents, 25 years before that 8 great-grandparents, etc. until we go back 40 iterations to find that I had 1 trillion ancestors at that time; this is more human begins than have been alive since the planet coalesced into its present shape. 40 iterations of 25 years is only 1,000 years so yes--I am related to you. All of you. Five times over.

Actually, the key point in Hashi's correctly stated apparent paradox is not so much that we're all related fairly closely to each other... although we provably are. It's actually that we're all the result of some considerable level of distant incest - for want of a better word. (Well, I say correctly stated, even though 40 iterations of 25 years is actually 2,000 years, rather than 1,000). However, I'm nit-picking...

It's clearly impossible for one single individual to have 1 trillion separate individual ancestors. Therefore, as one goes further back along one's family tree, the same ancestors must obviously pop up multiple times on one's maternal or paternal sides - in fact it's almost without doubt that innumerable ancestors appear multiple times on both sides of your (and everyone else's) personal genealogy.

[peter]

The phenomena Murrin is refering to is (I think) called genetic collapse. re the leaving of Africa, the two waves of modern human migration apparently occured approximately 65,000 and 45,000 years ago, but it should also be noted that *Homo erectus* had achieved an almost world wide spread one million or so years before. One interesting point I have garnered (I'm reading a short history of humanity at present which has sparked these questions) is that apparently there is more genetic diversity to be found between two villages in Africa 20 miles apart than there is across the whole continent of europe. This apparently is a reflection of the massive period of time that humans (or human forbears) spent in Africa and the proportionately small section that emigrated away to pastures new in the two waves mentioned above.

[Hashi Lebwohl]

Well, I say correctly stated, even though 40 iterations of 25 years is actually 2,000 years, rather than 1,000). However, I'm nit-picking...

Really? Are you sure? *poke* It must have been a late night last night.

[Zarathustra]

I want to return to the questions of speech and consciousness.

Every parent has watched this "evolution" in miniature form. They watch their children go from speechless animals to fully sentient, intelligent, self-conscious beings. Just yesterday, I was wondering to myself how I ever taught my son how to understand the word, "tomorrow." How does a baby understand a dimenision of the world that is perpetually on the "other side of" now? Clearly, in each of us is the potential to understand such concepts long before we have the words to do so. The words themselves aren't even important, because every human language has a different sound for this concept. It's not even the grammatical structures that open the doors to the possibility of acertaining this concept, because there are human languages with vastly different grammar. Even if the sheer, raw awareness of cause and effect (built up over time through experience) is all it takes to provide access to this concept of future, how the heck does the baby know that this concept is what the parent means when he says, "tomorrow?" How do they match the two up (i.e. concept + word)? I suppose it's all in context, but for the life of me I can't imagine how that happens. I know I didn't sit down with a calandar and point to successive boxes and say, "yesterday, today, tomorrow," like I did for colors, numbers, letters, etc. Sesame Street doesn't have a Temporal Concept of the Day; there is no Count Tomorrow. So how did my son know when I said these words that they could be applied to his burgeoning concept of time?

I think pondering these questions are very similar to asking how the ability arose within humans in general. Obviously, our need to express ourselves didn't shape brain evolution. That's teleological. Lamarkian evolution. Striving for higher branches didn't make giraffes' necks longer. So humans must have found themselves in a position very similar to our own babies: nature gave them a larger brain with the capacity to speak, and they merely put it to this novel use ... just like we've turned a hand used for grasping trees into a tool for typing on keyboards. Now, for humans in general they were given these brains via mutations over many thousands of years, compared to the DNA "program" for our babies that encapsulates this chain of evolution in a much shorter time. But it's still the same mutations, either considered all at once or one at a time. Nature selected those mutations which were successful in terms of producing better speech (because speech conferred survival and breeding advantages), so in that sense there was an interaction between how we put our brains to use and how our brains evolved. But really, the bigger brains had to come first, just as it does with every child. Speech development may shape a child's brain development to some extent--such that their brain would process information differently if they never learned to speak--but it wouldn't shape the actual DNA code which contains that potential for brain development. And neither would it do so for human evolution in general.

So, it's really just an accidental direction of mutations, which we then took advantage of. But natural selection isn't random, even though mutations are. That which is conducive to passing genes on to the next generation makes unlikely possibilities quickly spread (relatively speaking) into ubiquitious traits. And there are certain traits that are so useful, that many different lines of evolution converge upon them. Flight, for instance, has evolved separately in insects, birds, and mammels. And it's true that many species have some form of language. Being able to share information across an entire species confers tremendous survival and breeding advantage.

In fact, I believe that consciousness itself is the greatest survival tool. A melding of physical and mental, a joining of a lifeform with its reality in a way that strives for the existential truths of its reality--not merely the contingent facts of "eat this" or "fuck that." But also "reality is temporal" and "this is a particular member of a class of universals." I think even animals must understand to some extent these existential truths, even if it's merely instinctual rather than conceptual. The world is such a place that lifeforms within it rise in complexity through evolution until they become "loops" within reality itself, little pockets of matter that relate to their own reality in a way that transcends the material of their matter, and apprehends the matter's forms, structures, and existential context. Thus, they become conscious, intelligent, because the world itself is the kind of place where instances of self-replicating order (which is all life is, when you get down to its most general description) are accelerated and facilitated by an awareness of order and an awareness of self. This is language: being in tune with one's own reality. And since reality is ordered/structured itself, this "being in tune with" takes the form of intelligence, which is then expressed in language.

And that brings us back to the question of consciousness within the evolution of humans. While I think our global society has forced a convergence of the consciousness we have now, I don't think we can assume that people 100,000 years ago had the same kind of consciousness that we do today, merely because they had the same kind of brains. Once language is introduced, you get various feedback loops where the consciousness can be shaped by language in many different ways. While language can facilitate our awareness of the world's order, as it grows in complexity it can also act as a filter to that order, substituting its own structures for a true or accurate representation of the world's order. The entire history of philosophy is full of this kind of filtering and coloring. In fact, several later philosophers (e.g. Hiedegger) have said that philosophical quandaries in the history of philosophy are largely confusions and misuse of language. To quote Bill Clinton, it often depends on what the meaning of "is" is. There have been many attempts to make our langauge more rigorous and accurate, to put it on a sound foundation (e.g. Russel, etc.). But we're very good at layering metaphysical interpretations upon the physical world. We populate reality with Heavens and spirits and gods and all sorts of things that twist our relationship with reality away from reality itself. Belief systems are virtual realities just as much as the Matrix. The fact that we look at the same stars that the ancient Egyptians did does not at all mean that we see the same thing.

[Avatar]

Well, you should probably read the book I'm busy on, The Language Instinct by Steven Pinker.

He directly addresses the question, suggesting that the mechanisms of language are innate and genetic.

I'm not very far, but as I said elsewhere, he's making a quite compelling argument.

--A

[peter]

Granted Z the argument 'speech---> big brain---> more speech--->bigger brain would be lamarckian, but how about:-

'genetic mutation produces increase in size of brain area dealing with communication--->better communication--->increased survival of individuals with gene that produces better communication---->more mating between individuals with increased communication---->enhancement of the effect + genetic mutation that produces yet further increases the size of the brain dealing with communication-----> etc, etc.'

In this way the increased survival chances of better communicating individuals along-side mutations that bring about this effect, contrive together to drive forward brain size and communicative ability to the point when *Bingo!* all of a sudden the brain discovers it can use it's new found power in the way you suggest, to do a multitude of other things (as well as to communicate [and formulate] more and more abstract things).

Regarding the concept of 'tomorrow' and a child's grasping of it. Clearly the child's ability to 'get' this idea is inate. Very few parents would ever think so far as to even attempt to convey this idea to thier infant child and yet never have I met a person in my 60 odd years who did not understand what 'tomorrow' was (and that it never comes). But I would suggest that there was a time, at some distant point in our past when this idea was not inate. A squirell hiding a store of nuts may have some cloudy idea of a future where those nuts will be of use (I don't know) but for sure he will not have the idea of 'the future that never comes' - the idea that is intrinsically tied up with ther concept of tomorrow. At some point in the evolution of the human brain this idea had to pass from being a non-inate idea that the increased power of communication could transmit (and be understood) to an inate 'framework' that required only the drapery of the appropriate language to bring it to fruition. [Actually the squirell analogy is a bad one because it begs the accusation of confusing 'ontogeny with philogeny' IIRC].

re the 'evolution of conciousness' it seems almost inconcievable that the way we are aware of ourslves and the world we live in would not be insome way colored by the state of our knowledge about ourselves and the world we live in and so for this reason alone I'd hazzard a guess that human conciousness would be a changing thing over a period of time. Is that change always for the better - questionable. There is more than one example where evolution has not resulted in the best or most advantageous charachteristic being carried forward and in any case would a thing like 'concious' be subject to the ordinary rules of natural selection anyway.

[peter]

Sorry for the double post mods, I have a few new developments pertaining to this

By chance I have stumbled upon a book called 'Last Ape Standing' by Chip Walter which deals with the very subject of this post. The book is by no means perfect (at one point Walters seems to confuse Darminism with Lamarcism when he describes one of the factors in large brain development as being the increase in brain size that is seen to occur in animals placed on starvation diets) but does throw up some interesting stuff.

A case in point is the identification of possibly the first - or at least a very early - mutation that set us on the road to becoming human. Other primates it appears have a straight big toe in the foetal stage of their development but prior to birth this arrangement modifies to give an opposable digit analagous to the thumb on the foot. For effective bipedal walking, the presence of the big toe as we have it is essential, bearing as it does, some 30% of the bodyweight during each stride. In humans this re-arrangement of the first digit of the lfeet does not occur. Individuals with this 'mutation' would be rubbush at climing trees - but would have distinct advantage on the savanah where an upright gait is both more efficient and advantagious in a predator laden environment. Interesting that such a huge effect might come from such a, on the face of it, minor cause.

[Avatar]

IIRC, the ankle was also a significant factor in terms of adaptation.


--A

[peter]

Gosh - I'm learning lots from Chip Walter and his slim volume. Like for example were (god forbid) a child to be blind folded from the ages of three to five, when the covers were eventually removed at the age of five the child would be blind. Not through eye degeneration, but because after five the areas of the brain involved in interpreting sensory information from the eyes have 'set' to the point where no further change can be brought about. Prior to three the area is still plastic enough to be able to adapt to incoming information. One reason why we cannot recall anything much befor thage of three is because the brain is insufficiently developed enough for the memory centers to be fully functional before this age. The early brain (we are told) may be thought of as a plain of virgin heather. As we walk through it we leave a track, but if we don't continue to use that track it soon dissapears. Similarly with a particular learned trait. If however we use it over and over it becomes a road that ultimately becomes fixed and nothing further will grow on it, but neither will it dissapear. Hence things learned by repetition early in life become fixed and then immutable. We are indeed made by the cumulative effect of aour experiences in early life. The jesuits said 'give me the child until he is seven and I will give you the man'. They were right.

One anecdote in the book concerns the anthropologist Colin Turnbull who in the 1950's took a member of the jungle dwelling pygmy tribe, the BaMbuti, out onto the savanah where in the distance they saw a group of bison grazing. The tribesman asked Turnbull "What kind of insect is this." Turnbull replied that it was a bison and the man laughed "Don't be so silly, bison are huge" he replied. Turnbull realised that the man had no experience of perspective changes over such a large distance, coming from the forrest where such a vista was never seen. The man literally could not see the animals a bison at a distance - his brain could not do it - and so he saw them as insects instead.

[Vraith]

I'll take this opportunity to recommend...at a high risk, cuz I only read it once, a long time ago, and at this point it might be just nostalgia...I remember liking it, so I might be crediting the science more that it deserved?? It's definitely old [70's when written, 80's when I read it]...so probably out of date.
But there was a book called "Descent of Woman," that addressed a number of things...many due to an enormous, long-term drought...the survivors, our ancestors, were those near the coasts...a partial return to the sea.
This accounted, IIRC, for women's breasts, human's hips, the missionary position, and leg structures, the fact that women tend not to lose their hair...and when they do, it is later in life. The giant range of motion of our shoulders, full-body fat layer, etc. Other stuff...basically, an account of evolution on the female side that male scientists had left out/hadn't explained satisfactorily. She did it fairly humorously as I remember...it wasn't a rabid man-hating rant...don't accidentally look at the plural titled one "Women," which is not about biology/evolution.