The human evolutionary line in Africa

By 5.8 million years ago (MYA):  Orrorin tugenensis is thought to have been first in the proto-human line that had, in its evolving, branched away from the chimp-bonobo line and onto its own path. About the size of modern chimpanzees, it evolved the ability to walk habitually upright on two legs, and had small human-like teeth with thick enamel.

 

By 5.5 MYA:  Ardepithecus, a major branch off the early proto-human line, was a forest dweller that retained many of the gorilla and chimp traits of its pre-human ancestors.

 

By 4 MYA:  Australopithecus afarensis combined upright walking with chimp-size “big” brains (380 to 440 cubic centimeters). It was the first human ancestor to live mainly on the mostly flat grassy savannah instead of in trees. The famous specimen known as Lucy lived in Ethiopia about 3.2 MYA. A similar ancestor, Paranthropus—a robust branch of the Australopithecines—lived in both forests and savannahs around 2.7 MYA, and had massive jaws for chewing tough vegetation and roots—a vegetarian if not a vegan.

 

By 2.5 MYA:  Homo habilis, meaning “Man” who is “able” or “handy,” overlapped in time with the Australopithecines before they died out. H. habilis appears to have been evolutionarily intermediate between the more primitive Australopithecines and the subsequent, more advanced, Homo species, but is considered the first definably “human” ancestor to modern Homo sapiens. Though it retained many ape-like features including a small brain (550 to 680 cubic centimeters), its face protruded less than earlier hominids.

 

Ardepithecus, Australopithecus and Homo are regarded as three phases in early human evolutionary emergence. By the time of Homo habilis’ appearance hominins had developed diets rich in meats, probably as both scavengers and hunters. It is thought possible that the extra energy thus derived might have enabled the subsequent evolution of larger brains—maybe (maybe not). Homo habilis had begun the tradition of making tools by striking rocks to knock off sharp flakes useful for cutting and scraping.

 

By 2-1.5 MYA:  Homo erectus had attained a brain size of up to 1000 cubic centimeters, stood up to six feet tall, and is considered the first true human hunter-gatherer. The stone tools fashioned by this important pre-modern human increased over time in complexity of shape and purpose, revealing emergence of culture-based learning. Similarly, evidence of the use of fire between 1.6 MYA and 780,000 YA has been found in Kenya and Israel.

 

There also is ample evidence that Homo erectus was the first to migrate out of Africa in large numbers around 800,000 YA, expanding eastward across southern Asia and on into Indonesia. A branch of H. erectus known as Homo ergaster, with a brain volume of only 850 cubic centimeters, remained in eastern and southern Africa and evolved into a subspecies known as Homo Antecessor. In turn, further evolution of H. Antecessor gave rise to a distinctly more modern branch of the human family called Homo Heidelbergensis.

 

By 600,000 YA:  Homo Heidelbergensis, with brain capacity of around 1220 cubic centimeters, was living in both Africa and Europe. Two more important human lineages emerged out of H. Heidelbergensis—the Neanderthals (H. Neanderthalensis) who are relatively familiar to most people, and the Denisovans (H. Denisovan) who are not, as their existence was confirmed only in 2010. Both roamed the earth for several hundred thousand years, quite longer than modern humans have so far.

 

It is not clear whether Denisovans migrated out of Africa to Eurasia, as Neanderthals did, or whether they emerged from H. erectus who had already left Africa behind. It is certain that as recently as 30,000 years ago Denisovans were living in, and left their bones in, a cave in southern Siberia—which means their stay on the earth overlapped for quite a long time with both Neanderthals and modern humans. Since our modern-human direct ancestors also had migrated out of Africa into Eurasia by around 60-70,000 years ago, overlapping as they did and needless to say, the three Homo human species interbred as was convenient, as human types always do. Modern DNA analyses leave no doubt of their amorous inclinations as opportunity arose.

 

By around 430,000 YA:  Homo Neanderthalis, had migrated from Africa into Eurasia, leaving evidence of habitation from Uzbekistan westward across Europe as far as Britain. Over 400,000 years they prospered—until they declined and went extinct from unknown causes only 28,000 years after modern humans, ourselves, also entered Europe and in not a few instances freely interbred with them. Being of 99.5 percent identical genetics to start with, the two species’ genes were viable interspecies, apparently in both directions, as certain Neanderthal genes remain alive and viable in modern Homo sapiens—or, one might say, in a hybrid Homo neanderthalis-sapiens. Neanderthal brain capacities averaged about 1600 cubic centimeters in men, 1300 in women.

 

Relatively little is factually known of the Neanderthals’ culture and habits, though opinions abound. Some say their swarthy heavy-browed likeness remains especially visible in the modern Balkans. Characterizing this likeness was the late Soviet figure Leonid Brezhnev, whose ancestry unfortunately can be traced only to nearby Ukraine.

 

Archeological evidence of emerging (rising) human intelligence and dexterity has turned up in many ways:  wooden huts near Chichibu, Japan are the earliest evidence of shelters built for a purpose (500,000 YA);  humans’ use of spears for hunting (400,000 YA);  oldest surviving footprints of three people descending the slopes of an Italian volcano (325,000 YA);  complex manufactured grinding stones and stone blades (280,000 YA).

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About 300,000 YA (or less), Homo sapiens emerged as a dynamic carbon-based biped species—slender, upright of posture, with high forehead and flat of face (no dog-like muzzle). We almost immediately began roaming out of Africa, and thence migrating eastward across Asia and westward across Europe. For many years human origins were placed at 200,000 YA, but evidence uncovered in recent years has firmly pushed this back to 300,000 YA. Early Homo sapiens brains averaged nearly 1500 cubic centimeters, a size subsequently evolved downward to about 1350 cubic centimeters.

 

Pause and consider:  Capacity of brain “size” does not necessarily connote capacity for intelligence or intellectualizing, and must be used with caution as a distinction between the higher Homos. While modern men average 1260 to 1350 cubic centimeters, the smaller brains of modern women and pygmies average about 1130 cubic centimeters, but no inequality of mentation is implied. These averages furthermore differ significantly among individuals, but do you know any large people with great big heads who seem any smarter than average? The modern human brain is not the largest in the animal kingdom. Neanderthal brains were larger, as are those of modern bottlenose dolphins, sperm whales and elephants. But within its volume, male and female, it accommodates by far the most intense, complex neuronal activity of any species on earth. Soft tissues don’t fossilize so we cannot examine those large Neanderthal brains to see if the gray-matter cortex was equal to modern brains. In dolphins, sperm whales and elephants they are not.

 

With our complex bodily structures and complex systems including our hyperactive complex brains, Homo sapiens is by far the most complex structure to emerge in the universe over the 13.8 billion years since the big bang. We, friends, are it—the most complex, the most upwardly risen, the most of the most—the summit of all self-organizing upwardly-emergent evolution since the Big Bang.

 

How then is it that we—and our elected, supposedly representative Representatives and Senators—can be so stupid that we are endangering our own survival with carbon dioxide pollution out of blind devotion to one particular method of economic exchange—among several equally good optional methods for accomplishing the very same thing—that is free market capitalism grown wholly out of control? I shall have more to say of this.

 

Accumulated evidence of human emergence

Two of the oldest certifiably Homo sapiens skulls lived out their mortal lives in Ethiopia. The direct motherly ancestor of every human alive today—mitochondrial Eve—lived her lifetime in southern Africa sometime between 156,000 and 120,000 years ago. This assertion too is supported by modern DNA analysis. It is considered possible, even likely, that humans had developed articulate language by 150,000 YA, though human vocalizations leave no fossils. If so, it almost certainly was accompanied by symbolic thinking, the likelihood of which is suggested by jewelry around 100,000 years old, including painted and pierced seashells found at Blombos Cave in Western Cape Province, South Africa.

 

Archeologists have also found the first evidence of long-distance trade between human groups, at least140,000 years ago, making the barter exchange of objects-possessed for objects-desired one of humankind’s most fundamental and characteristic intentional activities. Logic suggests this activity too was probably accompanied by language. This finding can also be called the genesis of economic systems. However…

 

…when trade has begun, we’re no longer discussing biological evolution, we’re well into the next phase—cultural evolution, an important phase covered in some detail in the next chapter. Before that, however, a few more things must be said about emerging-life evolution itself. Our focus is on its manifestation as the agent of change during fast evolution—the phase of the universe’s long evolution when life emerged on Earth.

 

Emergent directional complexity

As previously noted, the term evolution means “change.” In context of the evolution of living things, this means biological change that happens by chance, like Squeak Beak’s much-ridiculed little mutated beak. Out of this biological changing by sheer chance, ever-increasing complexity emerges. We saw how objects forming in the universe gradually became more complex after the big bang. It’s the same with life on earth.

 

It’s not a smooth process—not all evolution results in increased complexity. Things sometimes go three steps forward and two steps back. Sometimes they even go two steps forward and three steps back, so that some of the evolving goes the other way—de-volving—whereby living things become less complex, less able to survive, even to the point of going extinct as did the dwarf humans on Flores Island. Though evolution can and occasionally does go downhill, on average it does not. The downward-trending exceptions found in fossil records of extinct creatures are just that, exceptions—all were momentary setbacks in the grand upward sweep of evolutionary emergence.

 

On average, overall, instances of things that devolve are very much outweighed by the many other instances that display increasing complexity. And like that average annual worldwide temperature of global warming, the average of rising complexity is important. The prime example of examples is of course high-level mammalian intelligence today compared with an ancient world that was everywhere populated by, and only by, bacteria without much in the way of common sense. We have risen, we are higher. And it is self evidently true because…here we are. Both we and the universe we live in are greatly more complex than we used to be, before we evolved up to where we are at present.

 

The overall upward-trending is displayed in the formation of the universe, from big-bang chaos to ordered galaxies and solar systems, and in all living things that have emerged out of that universe. Algae and worms exemplify less (lower) complexity among lifeforms, while squirrels and ground sloths exemplify more (higher). To anyone with eyes to see and brain to think, this overall upwarding of Everything may seem obvious to the point of trivial. It’s as if we, along with our parent universe, are all on some grand journey, from “less” to “more”… and we wonder how the sheer chance of ever-evolving nature could do such a marvelous, wondrous thing. Notice the undeniable march of increasing complexity that just happened—organizing itself, all by itself:  first a big bang… then gas clouds… clusters of galaxies… single galaxies… stars… planets… lands and oceans… simple life… simple plants and animals… complex plants and animals… vertebrates… fishes… reptiles… mammals… hominids… humans… and then…

 

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Let us belabor the subject before passing on, for the obvious has been there to see all along but many have not seen and, even possessing learned degrees, still do not. Upward direction is observed fact. Leaving quite aside the apparent miracle of a universe that “just” poofed into existence out of nothing, then organized itself into grand clusters of galaxies, stars and planets, simply look at what has in fact happened on earth alone over the past three billion years. Simple life forms begat themselves—somehow—out of inert lifeless elements. Then, by some means unknown to anyone who wasn’t standing there watching, they managed to 1) survive and 2) “learned” how to reproduce themselves. From these beginnings so simple, evolution has in fact produced a steady stream of rises.

 

By “rises,” I mean progressively greater complexity than existed before—i.e., self-organization, living things emerging toward ever-greater and upward-trending complexity driven by a thoroughly natural process called natural selection. One of the products of one of those many branches of rising life forms is the fairly complex, definably intelligent species which we call ourselves. Yet there are plenty of scientists who will argue you into the ground on this very point. If I can write these lines and a virus cannot, my situation can reasonably be said to be “higher” than that of the lowly virus—even though it has been around longer than I have. To not call that “rise” is semantic quibbling. The current summit, life’s highest so far, didn’t have to be us. It could have gone any number of different ways. Yet the fact is here we are. Evolution advanced;  complexity rose;  we humans are the lucky outcome. Knock on wood.

 

Finally this:  For churchmen who think God controls everything and scientists who think evolution has no purpose or direction, the element of chance deserves extra emphasis. The notion of linear evolution straight up to Homo sapiens is a fiction. Rather than a straight line there were many zigzags, with many sideways meanderings and backslides along the way. Unarguably illustrating chance, at least twelve other fully human species—that we know of—within our own genus Homo evolved into existence, lived a good long time, and finally died out. The totally human species Homo neanderthalis, and Homo florensiensis, for example, half-sisters of Homo sapiens, walked this earth much longer than we have but for various reasons they eventually went extinct. Still, notwithstanding extinctions by chance, in comparison to where the universe  started 13.8 billion years ago and to where life started 3.5 billion years ago, and on average, the universe and all within it is higher now than then. It all trends upward, naturally.