Mankind Evolution Essay Questions

1. Are humans and apes different?

The science of genomics - the genetic study of the genomes and DNA sequence of organisms - helps explain this. The genomes of humans and apes differ by little more than 1%, but this in fact means there are over 30 million point mutations. For example, protein-producing genes affect brain size and speech. Some gene developments - or gene expressions - may lead to extinction, whilst others can cause innovation. This is enhanced by gene duplication, which encourage new functions which are related to, for example, brain size and immunity. Simultaneously, the human/ape divergence will also be enhanced by cultural and learning effects. The two are heavily inter-related. Much of what makes us human is cultural, passed from generation to generation by learning. What makes humans different to apes is based on an evolutionary circle - genomes build bodies and brains, which create culture, which alters genomes. At some point, possibly with Kenyanthropus platyops 3.5 million years ago, humans and apes diverged from a common denominator, and over time, this evolutionary circle has increased the divergence, resulting in human uniqueness.

2. Why did we start walking on two feet?

Was this to free our hands for tool making? No, because we were bipedal possibly 6 million years ago before we used tools 3 million years ago. Bipedalism involves anatomical changes. By 4 million years ago, the human lower leg was upright to the foot, where as the ape lower leg was angled outside the foot. Bipedalism was a gradual process - some climbing, some walking. Bipedalism probably evolved many times throughout the evolutionary tree. Bipedalism represented survival and adaptation to the environment. Almost 2 million years ago our ancestors left the trees for the savannah. Walking upright may have provided greater vision regarding predators, reduced direct heat and greater circulation, and allowed for greater ground coverage.

3. Was technological development rapid?

The oldest tools discovered - rock fragments to cut and scrape - are nearly 3 million years old. It was 1 million years later when the whole rock, not the fragments, was fashioned and used as an axe. This tool-making then evolved over the next million years. The whole process involved 'grasp' and language. Language is important because that implies 'culture' - the spread of knowledge; copying and informing. Social learning fuelled the technological revolution - gradually.

4. When did we start talking?

Language is enabled anatomically - neural connections to the tongue, diaphragm and chest muscles. As humans, we can breathe and speak without thinking. Apes have a balloon-like organ connected to the voice box which makes loud booming noises; humans do not. Homo heidelbergensis used language 600,000 years ago. Language - or communication - would have begun with hand gestures and sounds that mimicked natural faunal sounds. This would have encouraged social bonding and an obvious survival benefit, that then evolved into a proto-language which subsequently fuelled technological advance. The two would then have gone hand in hand.

5. When did art begin?

The big debate is where and when the ‘human’ cultural and symbolic development began. Some point to the cultural explosion that occurred in Europe some 40,000 years ago, as demonstrated by the dazzling display of Aurignacian art such as that found in the French cave of Chauvet. This implies that Europeans were the first to speak, paint, carve, dress, weave and exchange goods. Others, however, provide evidence in Africa millenia before. It comes down to the evidence. In Africa, Makapansgat is the site of the discovery of the Makapansgat pebble. This is a 260-gram jasperite cobble with natural chipping and wear patterns that make it look like a crude rendition of a human face. The pebble, found some distance from any possible natural source, was in the possesion of a female Australopithecus africanus, an early hominid living between 3 and 2 million years ago. The pebble was not a manufactured object, but it was possibly recognized it as a symbolic face, and treasured as such. This would make it the oldest known sculpture, or manuport [a natural object which has been moved from its original context by human agency but otherwise remains unmodified] known. The Tan-Tan sculpture, discovered in ancient river deposits of the river Draa, Morocco, is between 500,000-300,000 years old. The overall shape of this little quartzite pebble, almost 6 cms in height, resembles a human figure but is entirely natural and unmodified by human action. Found near stone tools, it is possible that the pebble was simply collected and kept by someone who noticed its human shape. Examination under a microscope suggests this shape may have been emphasised by deliberate alteration of the natural grooves which run across the body. Is this a work of art or a curio? The Berekhat Ram sculpture, discovered in the Golan Heights, Israel, is between 250,000-280,000 years old. It may be the oldest known representation of a woman. This tiny piece - only 3.5 cms in height - of volcanic scoria, reddened by heat and incorporating specks of charcoal does not immediately resemble a figurine. Largely natural, it is the groove around the neck and others on the sides which have been shown to be deliberate modifications absent from other scoria found in the area. The grooves accentuate the natural shape to suggest a human form which has been drawn as female. Does it represent curiosity or artistry on the part of the hand-axe makers of Berekhat Ram? The Blombos ochre piece, from the Blombos cave in South Africa, is decorated with a delicate geometric pattern and has been dated conservatively at 77,000 years old. In fact, archaeologist Chris Henshilwood who found the ochre, believes it could be as much as 100,000 years old due to the more recent discovery of paint-workshop artefacts in the Blombos Cave. The cave paintings of Chauvet are up to 35,000 years old. European Palaeolithic art developed over a period of 25-20,000 years and continued until the end of the last ice age, 11,000 years ago. But the art of this time in Europe was not restricted to the paintings and engravings found on the walls of caves. Portable art, though often under-represented, was prevalent during this period. Sculptures depicting human figures, animal figures and therianthropes [hybrid figures, usually a human figure with an animal head] have been discovered. The Vogelherd Horse, discovered in Germany, is between 35,000 and 32,000 years old. The Lion Man of Hohlenstein-Stadel, discovered also in Germany, is 32,000 years old. Of a similar age is The ‘Dancing Figure’ of Galgenburg, discovered in Austria. The Lespugue figurine, discovered in France, is between 24,000 and 22,000 years old.

6. Is a large brain important?

Brain growth encourages evolution. The strong jaw muscles of primates actually restricted the growth of the skull. This restriction disappeared roughly 2.5 million years ago with Homo habilis, probably as a result of climate and environment change. This change highlighted the benefits of 2 of our greatest tools - adaptability and social cohesion. Brain size increased [and intestines decreased] with diets of meat and seafood. The cooking of meat meant less effort was spent on digestion. As Stephen Oppenheimer states, rapidly increasing brain size was a key feature that set humans apart from the walking apes that lived before 2.5 million years ago. Since then our brains have trebled in volume. This increase was not gradual and steady: most of it came as a doubling of volume in Homo erectus 2 million years ago. The greatest acceleration in relative brain size occurred before 1.5 million years ago - early in our genus. Modern humans - and Neanderthals - living before the last ice age 20,000 to 30,000 years ago had bigger brains than do people living today.

7. Why did modern humans leave Africa?

It is now widely accepted that the dawn of humanity lies in Africa, and modern man’s ancestors originated on this continent. The birthplace of all new human groups has always been south of a great barrier we now call the Sahara Desert, leading to the phrase ‘sub-Saharan’ Africa. It was from here that our ancestors colonised the world. Journey of Mankind - The Peopling of the World - Genetic MapHomo erectus spread into eastern Asia 1.8 million years ago. Homo sapiens left Africa between 90,000 and 75,000 years ago. [They also left Africa heading north into the Levant some 120,000 years ago but did not survive]. No one can say definitively what led us out of Africa - our curiosity, the human need to journey, our forward looking imagination - or perhaps the basic instinct for food and survival. For most of the first 2 million years on Earth, we roamed the savannah as hunter-gatherers exploiting the rich nutritional value of group-hunted game, supplemented by salads of roots, fruit, and leaves. If climate change reduced the food supply, as populations grew, a new means of survival had to be explored. Modern humans were becoming more inventive and adaptive, in terms of technological, social and cognitive behaviour. This may have made us exploit new territory, sometimes to survive, sometimes to avoid competition.

8. Why is climate such a major factor for survival?

Food and water are obviously essential for our survival. As a satellite image of the world at night shows, the lights generated by the global population are predominantly along coastlines and up rivers. For the modern human diaspora out of Africa, climatology is a real entity, either as a window of opportunity - lower sea levels during glaciation affording further migration - or as a slammed door of disaster - fertile corridors suddenly turning to desert. As Stephen Oppenheimer suggests, ‘The forces that drove our adaptive survival against overwhelming odds in the African savannah are the key to our nature and to our extraordinary story. We were not ‘put’ here fully formed, thinking, talking, and unique among animals. We were specially selected and moulded by a fierce, blind, unthinking environment. Like all evolving species, we had ancestors and cousins who shared some of our abilities but perished in adversity. Our physical and behavioural adaptations were focused on surviving the struggle with our greatest enemy and stern teacher, the climate’. ‘Once we had left Africa, although our brains had stopped growing, the climate continued to dominate human expansions and inventions right up to the modern age. It may be no exaggeration to say that the forces driving the waves of human technical innovation advancing across Eurasia from 80,000 years ago were more a result of stress and relief than of any biological improvement in the human computer. For example, the spreads of new technologies labelled by archaeologists as Early, Middle, and Late Upper Palaeolithic, Mesolithic, and Neolithic all coincided with dramatic ameliorations of Europe’s climate and population expansions into new territories. These events were mirrored in Southeast Asia with expansions and advances of boat-building and sailing in response to the flooding of continental shelf as the sea level rose and fell.’

9. If we are all related, why don’t we look the same?

Skin colour, hair, shape of the face and eyes are again determined by climate. In ‘Out of Eden’ Stephen Oppenheimer explains this: ‘The most obvious physical difference between peoples of Eurasia is their skin colour, which tends to be darker in the sunnier tropical regions. This is no coincidence. Skin darkness, which depends on the pigment melanin, is controlled by a number of poorly understood genes and is also under evolutionary control. For those who live in tropical and subtropical regions, the risk of burns, blistering, and the likelihood of death from skin cancer induced by ultraviolet light is dramatically reduced by having dark skin. There are other, less dramatic advantages: for example, the melanin in pigmented skin allows it to radiate excess heat efficiently, as well as protecting against the destruction of folic acid, an essential vitamin. So in sunny climes, over many generations, people with dark skin live on average longer and have more successful families. In North Asia (i.e. Asia north of the Tibet-Qinghai Plateau and east of the Urals) and Europe there is less sun and a lower risk of skin cancer, but there is the ever-present risk of rickets, a bone disease caused by lack of sunlight that was still killing London children even at the beginning of the twentieth century. ‘So there are at least two evolutionary selection forces working in concert, tending to grade skin colour according to latitude. The sun-driven change in skin and hair colour evolves over many generations. From the available genetic evidence, Africans appear always to have been under intense selective pressure to remain dark-skinned. Outside Africa, though, we can see gradations of skin and hair colour as we move from Scandinavia in the north of Europe and Siberia in the north of Asia down to Italy and Southeast Asia in the south of those regions. The darkest-skinned groups of non-Africans still tend to live in sunny and tropical countries. Clearly, if change in skin colour takes many generations, we shall sometimes find people whose recent ancestors have moved to live in sunny countries and who are still fair skinned (and vice versa). A good example is Australia, a sunny country where the majority of today’s inhabitants are pale-skinned descendants of recent immigrants. Australia has one of the world’s highest rates of skin cancer, and this has already started it on the slow evolutionary path that will eventually lead to descendants of Europeans becoming generally darker-skinned. Conversely, the first visitors to the north of Europe and Asia probably started their journeys looking very dark skinned and evolved to become paler later. Apart from exceptions such as Australia, the average skin colour around the world is thus tuned to the relative amount of ultraviolet light. ‘Other, more solid differences, such as the shape of our face, are determined by the underlying skull bones. These do vary between different parts of East, Southeast, and South Asia, and imply a rather long period of separation between the populations of these regions. Throughout East Asia we see the Mongoloid type with an extra, so-called epicanthic fold protecting the upper eyelid, and broad cheeks and skull. This type is often further divided into Northern Mongoloid and Southern Mongoloid, with the latter showing a less marked eye-fold and including southern Chinese and darker-skinned Mongoloid types in Southeast Asia. A great variety of peoples is found in South Asia, particularly in India. The majority of Indians, although dark skinned, are more similar physically to Europeans and Middle Easterners than they are to East Asians. Europeans, with their long, narrow heads, round eyes, and pale skin are sometimes called Caucasian. The farther north in India and Pakistan we go, the closer is the physical resemblance to ‘Caucasoid’ Levantines and Middle Easterners. In southern India, darker-skinned, curly haired, round-eyed peoples predominate. In eastern India, Assam, and Nepal there are
peoples with a more Mongoloid appearance.

10. What happened to the Neanderthals?

Did modern humans breed with other genus types? Why is there Neanderthal DNA in the human genome? Were Denisovans a different species to humans? Some scientists believe that humans mated with other populations. Others disagree with the interbreeding hypothesis: the presence of Neanderthal DNA, for example, in the human genome may be due to the genetic makeup of ancient hominin populations in 'pre-divergent' Africa.

11. What about hybrids?

100,000 years ago, the Neanderthals existed far and wide across Europe and Asia. By 24,000 years ago, they had become extinct. One theory to explain their demise is that modern humans, as we occupied these regions, brought diseases that the Neanderthals could not fight against. Or it may have been competition for resources of food. Some scientists argue that Neanderthal archaeological sites do not show signs of direct contact, and it may have been climate change - an erratic climate - which restricted the hunting for this species which was less adaptable than humans.

12. Is there anybody else?

Scientists agree that other hominin species coexisted alongside our ancestors throughout prehistory. The relatively recent discovery of Homo floresiensis (right) on the island of Flores, living until 18,000 years ago, may be a case in point. The even more recent discovery of the Denisovans, discovered in Siberia but spreading as far south as Indonesia approximately 40,000 years ago, may be another.

13. Are we still evolving?

Humans are still subject to evolutionary pressures. Genetic changes are still occurring in order to adapt and respond to changing conditions - despite cultural and technological innovations. In humans, these changes are considered to be microevolution, whereas the Origins archive which looks at the whole hominin evolutionary tree is macroevolution. Changes of the human genome are manifested in, for example, lighter skin and blue eyes in northern Europe, partial resistance to diseases such as malaria among some African populations and lactose-tolerance in Europeans but not Chinese and African. The continued surge in global population will also lead to faster evolution as more mutations occur.

Wherever our origins ultimately lie, there is no rational doubt that we Homo sapiens are proximally the product of an eventful evolutionary past.  Our ancient history is richly documented by a fossil record that is remarkably abundant for one single family of primates, and that is certainly a lot better than most paleoanthropologists are prepared to concede as they write funding proposals for more fossil exploration.  Saying this is not, of course, to deny the huge value of such exploration.  Fossil records are by their nature incomplete, and in a science in which every answer leads to compelling new questions, it is important to flesh them out as much as possible.

Still, what we already know allows us to construct a fairly convincing outline sketch of human prehistory, and of the natural context in which it played out.  What’s more, as members of an intensely curious species that instinctively wants to know the “why” of everything, most of us are naturally interested in knowing more about this drama of human becoming.  But in trying to learn as much as possible about our evolutionary background, are we merely satisfying an innate genealogical inquisitiveness?  Or can we take this enterprise beyond the satisfaction of superficial curiosity, to discover more profound implications about ourselves and our essential natures?  I would argue that we can, and indeed that only by knowing the nature of the process that produced us can we begin to understand the rather bizarre and contradictory ways in which humans sometimes behave.

Several years ago, I attracted some mostly good-natured ribbing from friends and colleagues by arguing that we can learn nothing about human nature from studying the deep human past that we cannot learn by looking around at ourselves today, in all our murky complexities.  And while this claim might seem rather an odd one for a paleoanthropologist to make, I still believe there is truth in it.  Our species is fully integrated into the Great Tree of Life that unites all living things.  But there is nonetheless something about the way in which modern Homo sapiens mentally processes information that makes our species qualitatively different from all other creatures, including our own evolutionary predecessors.  In purely historical terms, we are not simply an extrapolation of any trends those predecessors might have embodied.  Still, the emergent nature of our cognitive processes most emphatically does not mean that there is no value in closely scrutinizing the long process that produced us.

Why Evolution Matters

This is because the exact manner of our evolution cuts straight to the heart of who we are.  There are basically two possibilities here.  If our biological history consisted simply of the gradual modification of a central hominid lineage over the eons, as most of us were taught in school (if evolution was mentioned at all), then we might legitimately conclude that natural selection has in some sense fine-tuned us to an identifiable human condition.  This would certainly be the clear implication if our fossil and archaeological records were to show that slow and steady biological and technological change was the rule among our extinct predecessors.  But if, in contrast, those records were in fact to reveal a picture of diversity and morphological experimentation, interspersed with periods of nothing much happening, the inference would be entirely otherwise.  If we were to find a bewildering variety of hominid species, all buffeted over time by the vagaries of climate and habitat change, the conclusion would have to be that the species Homo sapiens is simply the eventual victor in a long-running battle for ecological space among diverse hominids living in a constantly changing world.  Under conditions like these, long-term refinement would not have been the issue for our precursors; immediate exigency would have been what counted.

Homo sapiens is the only hominid species in the world today.  This clear reality intuitively favors the first scenario, in which our predecessors gamely and single-mindedly struggled toward the end-point that is us.  And as a result, paleoanthropologists have all too often tried to reconstruct hominid history by projecting our lone species far back in time, via a lineage of increasingly primitive predecessors.  But over the last few decades, as the hominid fossil record has increased by leaps and bounds, such views have become ever harder to justify.  In 1950 it was possible for the great evolutionist Ernst Mayr to argue that human phylogeny consisted of a mere three species in a single lineage.  But by 1993, my first attempt at a hominid genealogical tree already contained twelve species, spanning the past four million years.  The latest version of that tree covers seven million years and twice as many species, with as many as seven separate hominid lineages coexisting at a single point in time.  The very clear implication of this very bushy family tree is that there was no single central tendency in hominid evolution.  Rather, new variations on the hominid potential were continually thrown out to compete in the ecological arena, until one species finally emerged that somehow contrived to eliminate the competition – an event that was (very significantly) entirely unprecedented in all of hominid history.

A closer look at the details supports this broad picture, and helps us understand the complexities of how our unusual species came to be.  The earliest possible fossil hominids come from African sites between about seven and four million years old.  They make an oddly assorted group, united mainly by the claim that they moved upright when on the ground.  Terrestrial bipedality was definitively established over four million years ago, among “australopiths” that had ape-sized brains, projecting faces, and small bodies that retained excellent climbing capabilities.  This basic structure remained essentially unaltered for over two million years, although behaviorally something crucial happened with the first manufacture of stone cutting implements about 2.5 million years ago – almost certainly by an australopith.  Essentially modern body form seems to have emerged at less than two million years ago, but in the absence of any technological change.  Such change had to await the invention of the “handaxe” at some time over 1.5 million years ago, at which point taller obligate bipeds assigned to our genus Homo had already been in existence for some time.  The next major technological leap came over a million years later, when several species of the genus Homo had already come and gone.  The pattern is clear: technological and biological innovations in human evolution were both highly sporadic, and unconnected with each other.

Evolution and Who We Are Today

Our anatomically distinctive species Homo sapiens arose in Africa at about two hundred thousand years ago, but again in the absence of any evidence for significant behavioral change.  Only some one hundred thousand years later do we begin to find early indicators of the symbolic mode of cognition that today sets our species apart from all others, living and extinct.  To cut a long story short, our ability to form complex associations in the brain makes us modern Homo sapiens uniquely able to deconstruct and re-form the world around us in our minds, and to visualize alternatives.  And evidently, while the potential for this radically new cognitive mode was most likely acquired with the developmental reorganization that gave rise to our distinctive anatomy, its novel uses were discovered only significantly later.  Since the biology clearly had to be in place already before it could be used, the momentous discovery of our new potential must have been spurred by a cultural stimulus, plausibly the invention of language.  This would actually have been a routine “exaptive” evolutionary event, comparable to the tardy discovery by ancestral birds that they could use their feathers to fly.  So, purely in terms of evolutionary mechanism, there was nothing special about the emergence of our functionally altogether remarkable species.

The pattern of human evolution I have described has huge implications for the kind of creature we are.  When we single out particular human characteristics, it is easy – and tempting – to make up a story about how each one evolved, and about how each is adapted for some purpose.  But in any species huge numbers of features are inextricably bundled together, both in the genome and in the entire functioning individual.  And this makes it difficult to see how each could have been refined individually over the eons by classic processes of natural selection.  More commonly, natural selection on the individual turns out to be a stabilizing influence, while a lot of the evolutionary pattern we empirically observe reflects not individual reproductive success, but the fates of entire populations and species.  What’s more, we see few if any indications of steady progression in the human fossil record: something that is hardly surprising since we evolved over a period of notable environmental instability.  Combine such considerations with the empirical evidence of multiple hominid speciations and extinctions, and it is hard to avoid the conclusion that individual human beings can have been programmed by Nature for few if any specific behavioral function(s).

Our remarkable ability to create new realities in our minds wonderfully enables us to perceive things that lie beyond the material and the scientifically accessible.  This ability is essentially limitless; for although we are individually formed and bound by social influences of many kinds, there are no clear intrinsic restrictions on how we express our cognitive capacities.  On the plus side, this lack of constraint provides the basis for our free will.  But being unconstrained has its dangers.  And these furnish the principal reason why we should indeed care, deeply, about accurately understanding the nature of the process that produced us.  For knowing how non-directionally we evolved not only helps us comprehend why our behaviors are so frequently conflicted, contradictory, and unhelpful, it also forces us to realize the extent to which we are individually responsible for them.

Questions for Discussion:

1. Are human beings the product of long-term evolutionary trends?

2. Did technological and biological change proceed hand-in-hand in human evolution?

3. Is modern human cognition adaptive?

Discussion Summary

The argument in my essay was based on the premise that understanding the process by which Homo sapiens came into existence is crucial for understanding the kind of creature we are.  A slow process of gradual transformation and fine-tuning over the eons under the guiding hand of natural selection has profoundly different implications in this respect than the external-event-driven scenario that the bushiness of the human family tree seems to favor.

The very first comment submitted bore heavily on this issue of pattern, asking about evolutionary psychology, a field in which the fine-tuning of ancient behaviors is paramount.  Those of our behaviors today that seem to be mismatched with an expected optimum, are viewed as adaptations to an “environment of evolutionary adaptation” that no longer exists due to recent changes in human lifestyle.  However, the evidence seems to be overwhelming that, rather than having been finely honed by selection over vast periods of time, hominids in general are in fact hardy generalists.  They have been able to accommodate, especially with the aid of material culture, to a wide variety of circumstances thrown at them by changing Ice Age environments.  The evident fact that our species was eventually able to displace all of its hominid competitors in a rather short space of time is almost certainly due to its apparently rather abrupt, and recent, acquisition of its unique symbolic cognitive mode.  It is this that explains why Homo sapiens is the lone hominid in the world today, rather than one species of many.

This adventitious, non-directional history also emphasizes the extent to which we are individually responsible for our behaviors.  We cannot blame adaptation to an imagined “environment of evolutionary adaptation” for our often bizarre behaviors.  Those behaviors may, of course, be conditioned by past experience or present circumstances, but they are in essence a matter of choice.  We have not been programmed by natural selection to be a particular kind of creature, and it is this quality of free will that makes us individually answerable for our behaviors, both to ourselves and to society.

The second major thread running through commentary on my piece is the metaphysical one, bearing on the question of whether understanding our cognition, the way we apprehend and process information about the world, is actually a proper subject for science at all.  The principal commentator is certainly right to suggest that we do not understand how the brain translates into mind.  But although it is possible that we will never know (and such knowledge would indeed offer a frighteningly reductionist prospect), the question of how what we experience as our consciousness is generated has been a very valuable heuristic in driving studies of how the human brain works.  This is very much the province of science.  But, as the commentator points out, those in different fields have to be very careful about the way in which they use their words.

The nature of our awareness also came in for some comment.  There can be no doubt that, at a very basic level, all organisms are “aware.”  Even unicellular creatures distinguish between “self” and “other,” and many living things show quite complex forms of awareness, as demonstrated by their reaction to outside stimuli.  But there is nonetheless something very unusual about the peculiarly human state of awareness, the thing that we denote as our “consciousness.”  Our ability to remanufacture the world in our minds, and to react to the world as we reconstruct it, rather than as we directly experience it, seems to be qualitatively different from any other cognitive state we can observe in nature.

This ability equally gives us, and also as far as we can tell uniquely, the ability to experience the spiritual, in other words that dimension of human experience that is accessible not directly through our senses, but through our minds.  It is spiritual perception that allows human beings to conceive of themselves as “embodied spirits” that are in relation to an “infinite being.”  Such matters lie well beyond the purview of science, though our ability to conceive of them demands that we address them.  Metaphysics is only one of several fields attempting to do that.  Such endeavors are critical to the full range of human experience; and they are entirely complementary to the effort to understand the material world, rather than competitive with it.  This suggests a couple of Big Questions that it might be useful for this forum to clarify:

  1. May evolution be related in any way (or not) to the existence of an Infinite Being?
  2. Does the relationship between the Material and the Immaterial extend beyond the human mind?

0 thoughts on “Mankind Evolution Essay Questions

Leave a Reply

Your email address will not be published. Required fields are marked *