Human evolution
By Paul Cooijmans
Introduction
Opinions differ on how humans have come to inhabit the world; Some think we really are pure mind, and have descended into material forms many times over the past few billions of years. Others believe it started with Adam and Eve, created by God. Again others say aliens from outer space landed here and interbred with apes, resulting in us; and currently popular is the theory we evolved in Africa about 100 000 years ago and spread out from there, replacing all other humans already living in Europe, Africa and Asia.
I became interested in the scientific facts regarding this matter, and read a number of books and visited web sites about it. A review of what appeared to me follows. For consistency, I express time as "B.C." (Before Christ) throughout to avoid confusion with the unsatisfactory "years ago" that is often used in these matters. To express time in "years ago" is a bit like acting as the barge-hand who dropped his watch overboard at night and marked the railing with chalk to remember where to drag the next morning.
From Australopithecus to Homo
The, for humans, interesting phase of evolution starts about 2.5 million B.C. in Africa. Australopithecus afarensis (or perhaps another species of Australopithecus), an upright walking creature with a skeleton very much like modern humans, but a much smaller brain and matching skull, started a gradual transition into what is considered the first real human, Homo erectus. This transition took almost a million years. The first parts of these names, Australopithecus and Homo, refer to the "genus" in question; A genus is a family of species. The second part refers to the species. A possible third part refers to the subspecies (or race, which is the same). Important to know is that individuals of different species as a rule do not interbreed, although closely related species can interbreed, e.g. horse and donkey.
A circumstance that is thought to be relevant is that the "gracile" variant of afarensis, originally a herbivore, forced by drought began to eat meat as a scavenger (not necessarily as a hunter) and by picking up small crawling animals from the ground (like ants). The extra protein and energy thus taken in may have allowed their (highly energy-consuming) brains to become larger than was possible on a herbivorous diet. The "robust" variant, which stuck to eating the plants and leaves still available, did not develop a larger brain. Afarensis' original cranial capacity was similar to that of modern chimpanzees and averaged in the low 400s (cubic centimetres), while early erectus had about 900 cc, which is in the bottom range of currently living humans. The intermediate forms, the larger-brained gracile afarensis which are often called Homo habilis and not generally accepted as humans, averaged at 640 cc. Current humans have on average 1300 cc, with a range of about 900 to 1800 (It differs per sex and population).
Probably as a result of the larger brain, the habilis forms were able to use and make tools, and it is in particular this making of tools that is said to be unique to humans (The mere use of tools occurs in several other animals too). Habilis lived from somewhere between 2.5 and 2 million to 1.5 million B.C., and it is thought they were not one well-defined species but several parallel forms, of which perhaps only one evolved, via another intermediate stage that has been termed Homo ergaster, into Homo erectus while the other vanished. Erectus appeared around 1.8 to 1.6 million B.C. Even though one believes they evolved in Africa, the oldest erectus fossils have been found not too long ago in Georgia, Asia.
The larger brain went with changes in the skull surrounding it. This process of changing skull features goes on until today; Here is an overview of archaic versus advanced features:
Archaic
• Receding lower jaw ("no chin");
• Big teeth (adapted to chewing raw food);
• Projecting upper jaw and middle part of the face (to allow for big teeth; a "round" face therefore);
• Pronounced brow ridge above the eyes (interrupted in the middle in less archaic forms);
• Receding forehead;
• Relatively flat low top of the skull;
• High attachment of the neck muscles at the back of the skull (a high neck).
Advanced
• Projecting lower jaw (a "pronounced chin");
• Small teeth (adapted to chewing cooked food which is easier);
• Less or not projecting upper jaw and middle part of the face (possible because of the smaller teeth; a "flat" face therefore);
• No or very small brow ridges above the eyes;
• Steep or vertical forehead;
• High round top of the skull;
• Low attachment of the neck muscles at the back of the skull.
Homo erectus populates the world
Between 1.8 million and 1 million B.C. erectus began to migrate from Africa to east Asia and Europe, arriving there some time before 800 000 B.C. (southeast Asia) and before 700 000 B.C. (Europe). China and the northern parts of Europe would be inhabited by their more advanced descendants somewhat later, because of the cold ice age conditions which required more adaptation.
With respect to population size one must realize they lived as hunter-gatherers, which requires fairly much surface area per unit of population. Realistic is about one person per 10 to 25 square kilometres, and much more than that would have meant overpopulation and food shortage, forcing part of them to migrate. So, success at increasing population size would have been a driving force behind their spreading out over the world.
In this period, erectus, thought to have been capable of some speech (though far from modern language and probably without grammar) which would have facilitated cooperation when hunting, learnt to master the fire on different locations and in different periods independently. Fire was useful for hunting, to inhabit caves, to stay warm, to keep wild animals away and to cook food. Chewing cooked food is easier, so this allowed for the transition to smaller teeth and less protruding jaws; to a flatter face. Cooking also transforms certain molecules in the food into forms more easily digestible, thus increasing the food's nutritional value. Cranial capacity increased to an average around 1100 cc for the later erectus. The upper limit of their cranial capacity is mostly given as 1225 cc, which is well into the range of current humans.
Erectus is usually said to have lived until about 250 000 B.C., but this rests entirely on how the fossils are classified; Much more recent fossils of erectus-like humans have been found and are being found now and then (just follow the news and pay attention), but one then tends to use location-specific or popular names and avoids explicitly classifying them as either erectus or sapiens. There is great reluctance to use the name erectus for humans who lived as recently as tens of thousands, or even thousands or hundreds, of years ago, probably because using that word seems incompatible with the presently dominant "Out of Africa" theory. It is now clear though that the recently discovered Homo floriensis of Flores was a pygmee variant of Homo erectus and its fossils have been dated as late as 10 000 B.C., while the current local inhabitants still know tales of the extinct hairy creatures.
"Archaic Homo sapiens" and Homo neanderthalensis
The forms that appeared between about 500 000 and some time after 100 000 B.C. are now usually described as "archaic Homo sapiens"; These are transitional forms between Homo erectus and Homo sapiens, with a cranial capacity averaging around 1200 cc. Should one choose to classify these under the species erectus, then the life span of erectus would extend much further than 250 000 B.C. The descriptive term "archaic Homo sapiens" is unsatisfactory in that it avoids assigning a proper species name to these transitional forms. I personally tend to include these forms, with their archaic skull features, with the species erectus, perhaps as a subspecies Homo erectus sapiens.
The "archaic Homo sapiens" forms lived in Africa, Asia (including China) and Europe (including the cold northern parts up to what is now Germany and Belgium). They were capable of dealing with cold better than was erectus. Many different names have been given to these transitional forms, often related to the place where the fossils were found, but the general descriptive term "archaic Homo sapiens" seems to have replaced those, except for in the case of Homo neanderthalensis; the Neanderthals. Neanderthals, a cold-adapted European form of archaic sapiens with a large cranial capacity around 1450 cc but archaic skull features, have been given their own species name. Some scientists have even included them with Homo sapiens as the subspecies Homo sapiens neanderthalensis, after which actual Homo sapiens had to be renamed Homo sapiens sapiens, but more recently one has been inclined to return to the viewpoint that they are a species of their own - Homo neanderthalensis (And subsequently our second sapiens disappears and we become simply Homo sapiens again).
The matter of how exactly to classify Neanderthals is related to the question whether or not they were (capable of) interbreeding with contemporary Homo sapiens; To call them Homo sapiens neanderthalensis would imply they were well capable of interbreeding, since with that name they would be two races of the same species. But nowadays consensus holds that Neanderthals did not interbreed on large scale with Homo sapiens, so that the name Homo neanderthalensis is more logical. It leaves open the possibility that they could interbreed, but says that as a rule they did not.
Neanderthals lived from about 250 000 to 25 000 B.C. Again, this first date is arbitrary and depends on how one classifies the fossils. Pre-Neanderthal forms were already present around 400 000 B.C., but those are mostly included with "archaic Homo sapiens". Neanderthals as a separate group vanished around 25 000 B.C.; They were either replaced by the Cro-Magnons who entered their territories coming from the Middle-East around 35 000 B.C., or absorbed into them by interbreeding. I now think the first is the most likely.
Homo sapiens
By about 90 000 B.C., some groups of archaic Homo sapiens had evolved skull features sufficiently advanced for them to be given the species name Homo sapiens. These lived in the Middle-East and in Africa. The ones in the Middle-East migrated to Europe where they arrived around 35 000 B.C., and are called Cro-Magnon, after the place where they were first found. These Cro-Magnons had an even larger cranial capacity than had Neanderthals, perhaps averaging around 1550 cc. They were technologically somewhat more advanced than Neanderthals, and also produced art. Like the Neanderthals, they buried their dead.
Cro-Magnons and Neanderthals both descended from erectus, but there is doubt as to whether Cro-Magnons were descendants from African erectus (via African archaic sapiens and sapiens forms who migrated to the Middle-East), or from European erectus. In the latter case, this would imply that European erectus, also called Homo heidelbergensis, split into two branches around 500 000 B.C., one in the north leading to Neanderthals, and one in the southeast leading to Cro-Magnons. Relevant in this respect is that the Pre-Neanderthal fossils found in Europe, dated 400 000 to 200 000 B.C., tend to display a mixture of Neanderthal and sapiens features, suggesting that European erectus had the potential to evolve into either. The later clustering of Neanderthal features into actual Neanderthals was adaptive in cold circumstances, while the clustering of sapiens features in humans from the Middle-East and Africa was adaptive in warmer areas.
Cro-Magnons as a group - to be regarded a race or subspecies of Homo sapiens - lived at least until 10 000 B.C. For thousands of years they co-existed in Europe and the Middle-East with the Neanderthals, which disappeared around 25 000 B.C. Around 10 000 B.C. the ice age ended, and life became easier in Europe. People from other regions - Homo sapiens, presumably - migrated to Europe and fused with or pushed out the Cro-Magnons, which therefore as good as vanished between 10 000 and 2000 B.C. People with apparently Cro-Magnon ancestry, called Cro-Magnoids, existed until about 2000 B.C. Currently, only the indigenous inhabitants of the Canary Islands (Guanches) and the Dal people of Sweden are thought to be pure Cro-Magnon descendants. Les pure descendants of the Cro-Magnons may be the Berbers of north Africa (in the remote past considered identical or closely related to the Guanches), possibly the Basques, and, more speculatively, some of the native American tribes.
Cro-Magnons were hunter-gatherers, but appear to have lived in a semi-settled way, inhabiting the same cave the whole year round for a number of years. This was possible because they made a more efficient use of the natural resources than did Neanderthals. For instance, they ate fish when available.
Advent of agriculture
Between 8000 and 4000 B.C., agriculture and cattle herding were discovered (presumably by the people who entered Europe after the end of the ice age, but also at several places elsewhere in the world in this same period), and the hunter-gatherers became or were replaced by farmers. Some think this may have resulted in a lower quality diet. Also, the groups which fused with or pushed aside the Cro-Magnons after 10 000 B.C. probably were less advanced and had smaller brains than the latter. They were only able to come to Europe after the ice age had ended, while Cro-Magnons had been living for over 25 000 years in harsh conditions already. In the milder post- ice age climate, there was less pressure for natural selection. All in all, this may have been a period of gradual degeneration resulting in modern Europeans, who have brains about 200 cc smaller than had Cro-Magnons.
Relevant about farming is that it allows higher population densities than does the hunter-gatherer life style. The word "overpopulation" means something entirely different for farmers than it does for hunter-gatherers; Farming may sustain several to several dozens of people per square kilometre, while for hunter-gatherers "overpopulation" means to have more than one person per, say, 10 square kilometres. This is important also with regard to the question of famine in the Third World.
Another fact on farming is that it requires higher intelligence than does the hunter-gatherer life style. To appreciate this, one may consider that many animals can hunt and gather food, but the only animal that can farm is also the only to have flown to the Moon.
Recently (2008) D.N.A. studies are said to have suggested that a large majority of Western Europeans are descended from the long-skulled hunter-gatherers who lived here during the last ice age (so that must be Cro-Magnons, although one avoids that term now), and a minority from those who entered Europe after the ice age (broad-skulled people now called "farmers"). These results would imply that the newcomers did not replace the Cro-Magnons, but rather that the latter adopted the new agricultural technology (and Indo-European language) and stayed in place. The further west you go, the larger the proportion of Cro-Magnon-descendants. The distinction between Celtic and Germanic peoples is probably not a genetic one but a cultural and linguistic one; The Celts are those who retained their original ice-age language, the others adopted the new Indo-European languages brought along from the east.
Australians
Meanwhile from southeast Asia, Australia had been inhabited some time before 40 000 B.C., possibly as early as 60 000 B.C. These people, presumably Homo sapiens by that time, came from Indonesia, and perhaps there was also a group from south China. Judging from their skull features, including those of living Australians, they had plausibly evolved from the east Asian variants of archaic Homo sapiens, which in turn descended from the east Asian variants of erectus. East Asia in particular is a region where there is continuity in skull features from the regional erectus to the regional, currently living, sapiens.
The popular "Out of Africa" theory though claims that ALL now living humans descend from a group of Homo sapiens that migrated from Africa after 70 000 B.C., humanity having gone through a "bottleneck" (near extinction) shortly before that and this tiny group being the only survivors. Since these were supposed to be anatomically modern, this theory seems to imply that, once in Australia, they must have evolved back into a form with archaic skull features (Current Australians still have projecting jaws, big teeth and pronounced brow ridges). Also, in the "Out of Africa" theory, the split between Europeans and east Asians supposedly took place around 40 000 B.C., which is not compatible with the archaeological evidence for inhabitation of north Australia (about 60 000 B.C.). To accept this earliest evidence of sapient life in Australia implies to reject "Out of Africa". I am therefore inclined to think that the "multi-regional" hypothesis is more likely; that is, the idea that erectus evolved regionally, via local archaic sapiens forms, into Homo sapiens, with of course migration going on.
However, recent genetic studies seem to confirm "Out of Africa", so if we accept that, it means Australia got only inhabited around 40 000 B.C. by the very earliest migrants from Africa, and the archaeological evidence for much earlier inhabitation has to be rejected.
The essential difference between "Out of Africa" and "Multi-regional" is that in the first the differentiation between present-day populations (races) was established within the last 70 000 years and most likely much later (the last about 12 000 years), while in the latter it was established within the last 1 to 1.5 million years. Unfortunately, this essentially scientific debate has become contaminated with ideology and politics, with Marxist intellectuals and the media generally supporting "Out of Africa" for other than scientific motives. "Out of Africa" is nearly always presented as an established fact in popular publications, documentaries, and in the news, and this is a misrepresentation of the actual state of affairs since it is merely a theory. What can be said is that modern genetic studies confirm "Out of Africa", but that the archaeological evidence in itself allows, and perhaps makes more likely, other interpretations.
Interesting about southeast Asia is that on Java there is evidence that erectus survived until as recent as 25 000 B.C. Given that Australia got inhabited well before that via Indonesia by people who still have archaic features, this makes one wonder; Were those migrants Homo sapiens by the time of migration (and if so, were they "Out of Africa", or were they Asian sapiens?), were they local archaic sapiens, or were they even local erectus? The answer to that question lies in the dating of Aboriginal art (ochre on rock paintings), assuming that the production of art is characteristic of Homo sapiens. Such work has been dated between 25 000 and 30 000 B.C., and there is indirect evidence for art up to 38 000 B.C. (which is as far back as carbon dating goes). Even more indirect evidence suggests artistic activity (but without surviving work) virtually since Australia got inhabited, which might be about 60 000 B.C. So they may have been Homo sapiens when they arrived, or otherwise they were local archaic sapiens and made the transition not too long thereafter (in which case this transition took place later than it did in Africa and the Middle East).
Again, recent genetic studies imply the Australians are "Out of Africa" sapiens who arrived not much earlier than about 40 000 B.C.
Americans
America got inhabited, as is now commonly assumed, via a land bridge to Alaska, by Asians, from about 13 000 B.C. on to the end of the ice age, when the land bridge disappeared again. The earliest Americans ended up in south and central America it seems, while the later migrants inhabited north America. It is possible the Americans came from different parts of Asia; the north Americans from the east, the central and south Americans perhaps from more western parts of Asia. However, there exist archaeological findings of mammoth hunters from Mexico that are as old as 20 000 to 25 000 B.C. (carbon-dated), that do not fit the current theory. If there were people there as early as that, they can almost only have come from across the Atlantic. Some also suggest that people from the Pacific islands have reached south America.
So if the current theory about America's inhabitation is wrong, it is most likely wrong about the south and central Americans, and least likely wrong about the most northern Americans who actually LOOK like east Asians and had the land bridge to help them get where they are. Other relevant facts in this respect are that some native south American peoples are said to look or have looked like Africans, and that the language of some American tribes is or was very similar to that of the Basques. Those facts fit a cross-Atlantic presence of humans in Europe, Africa, and America, well before Asians came to Alaska. Some connect this to the legend of Atlantis, and to Cro-Magnons as a sea-faring people. All in all, the origin of Americans is still puzzling at this time. Recent information, as usual presented as establish fact, holds that they did come from Asia after all, along the very edge of Beringia and then further along the west coast of America. Supposedly, that coastal edge was still inhabitable even though the rest of the land bridge was covered with ice then.
Civilization and intelligence
Remarkable in the prehistoric part of the era from about 10 000 B.C. on is the decline that seems to occur after peaks in civilization and technology. The people who achieved tremendous feats like building the various types of pyramids in various parts of the world, Stonehenge, the statues on Easter Island and so on, subsequently lost that ability and even forgot what the purpose of such works had been and how they had been built. In the light of the future of our current civilization it is of key importance to understand how this decline came about.
Considering what I know of intelligence and its relation to real life and society, such decline must have been caused by a decrease in modal (most occurring) intelligence in the population in question. Possibly also by a lower frequency or absence of genius. Apparently, modal intelligence rises in a population as an adaptation to environmental circumstances, initially to survive in the given environment. Once intelligence reaches certain levels, it causes forms of civilization to occur beyond mere survival, such as art, architecture, cities, large-scale organization, administration, ethics, and so on. But, once high civilization is reached, modal intelligence drops again, possibly through causes like relaxed selection pressures, various dysgenic effects, and migration. Then, they reached civilizational level is lost and sometimes even forgotten about. Other populations may pick up intelligence and civilization on their own meanwhile or thereafter. But whether the strain that degenerates will rise again anytime soon is doubtful. I advise not to take the risk.
Estimates of modal intelligence for various stages in evolution and civilization
Being interested in intelligence, I have tried to estimate the modal (most occurring) intelligence levels of the various populations and stages of human evolution. In this table they are expressed on the I.Q. scale where the current Western population has its mean at 100 and standard deviation at 15. These modes should be taken as the centres of actual modal ranges. For instance, a mode of 85 would mean that a large part of that population is within plus or minus 5 to 10 points from 85. Obviously, there exist individuals who are far removed from the mode, and important discoveries like tool-making and the mastery of the fire will have been made by the smarter ones from a group.
Similar estimations, expressed in terms of minimal modal I.Q.'s required for various stages of civilization; These are still modal I.Q.s of populations, not individual I.Q.s:
As an aside it may be noticed that when I.Q. levels are connected to civilizational stages like this, I.Q. becomes an absolute scale, rather than the merely relative scale it constitutes when derived from test score statistics.
Origin and development of the intelligence required for the higher civilizational levels
Societies with large-scale organization and other advanced features, that require a modal I.Q. of at least 80 according to the above section, have been founded by peoples who priorly had been living in areas with moderate to cold climates where they had to deal with periods of ice age conditions. In such periods they withdrew to places that were still inhabitable, but nevertheless many were undoubtedly killed by food shortage or cold, and those surviving were a select few.
When later the climate became better permanently (or when they migrated to more friendly areas), these were the people who became the founders of large civilizations. The raw ice age intelligence was then apparently invested, crystallized, into culture. And again later, it appears the intelligence that had led to civilization was in some cases lost, possibly because the selective pressure that had produced it (cold conditions) had disappeared, possibly also by other dysgenic effects that inevitably occur in high civilization.
The pattern seems to be that cold conditions produce peoples of high intelligence. This intelligence is initially of a raw and uncultured nature, visual-spatial and numerical rather than verbal. When conditions then improve, one uses this new intelligence to build civilizations. In that process, culture is produced, language refined, and verbal ability rises. For some time, overall intelligence may be rising as a result of increasing verbal ability. But then, through relaxed selection pressure and other dysgenic effects that are inherent to civilization, general intelligence starts going down, mainly on the visual-spatial and numerical aspects. Eventually, civilization may disappear again, or be taken over by another people still in the eugenic phase of this process.
Characteristic for the eugenic phase of this rise to civilization are high spatial and numerical ability, lower verbal ability, and an uncultured, "barbaric" nature. For instance, the medieval Germanic peoples, having been pushed southward by severe climate cooling, appeared barbaric to the degenerating latter-day Romans; and several centuries later the sophisticated Arabs, then at their cultural summit, were still appalled by the Germanics' bad table manners. The Germanics (or "Germans", as some say) however rose to civilization during the Middle Ages and became the world's leading culture in the Renaissance. Currently, some east-Asian peoples are clearly in this rising phase.
Characteristic for the dysgenic phase are high verbal ability (which facilitates deceit and relativistic philosophizing), decreasing spatial and numerical ability and therewith decreasing general intelligence, and a highly cultured, sophisticated, permissive, decadent-degenerative nature on the whole. Western civilization, the product of the Germanic peoples, has probably entered this phase in the second half of the twentieth century.
Human Evolution and Possible IQ Degeneration
Reply With Quote
Originally Posted by velvet
I think Nietzche talked of this in one of his books.
Bookmarks