Homo sapiens: What We Think About Who We Are (Revised and Updated)

From De humani corporis fabrica libri septem (1543) by Andreas Vesalius

In 1646, the first edition of Sir Thomas Browne's Pseudodoxia epidemica (or Vulgar Errors) first went into print, Browne's volume being an attempt to refute many of the erroneous "received tenets and commonly presumed truths" that would not go away despite their inaccuracy. Among the bevy of fallacious notions included in the book was a subject that often was a point of contention at the time; if the Biblical Eve was derived from one of Adam's ribs, from which side was the rib taken and therefore shouldn't the sexes differ in the number of ribs each possesses? While human bodies that found their way to dissection tables sometimes yielded an extra pair of ribs and were proffered as evidence of the inerrancy of Scripture, Browne saw through such post hoc interpretations of anatomy;

But this will not consist with reason or inspection. For if we survey the Sceleton [sic] of both sexes, and therein the compage of bones, we shall readily discover that men and women have four and twenty ribs, that is, twelve on each side.

[In Leroi 2003]

Over three and a half centuries after the first edition of Browne's book, however, the received "wisdom" that men and women differ in the number of ribs remains entrenched. How can this be so? While most people have never taken a course on human anatomy or studied a human skeleton with great care, many are at least familiar with the Genesis narrative of creation even if they do not ascribe to it. Christian fundamentalism aside, the first book of the Bible is still considered by some to contain some kernel of scientific truth, and it is to the Judeo-Christian creation story we must turn if we're going to understand how our ideas about our own species have dramatically changed.

20: And Adam gave names to all cattle, and to the fowl of the air, and to every beast of the field; but for Adam there was not found a help mate for him.

21: And the LORD God caused a deep sleep to fall upon Adam, and he slept: and he took one of his ribs, and closed up the flesh instead thereof;

22: And the rib, which the LORD God had taken from man, made he a woman, and brought her unto the man.

23: And Adam said, This is now bone of my bones, and flesh of my flesh: she shall be called Woman, because she was taken out of Man.

[Genesis 2:20-23]

Such a phenomenon recalls the discarded evolutionary doctrine of acquired characteristics most prominently associated with Jean Baptiste de Lamarck; because God took a rib from Adam to make Eve in the second Genesis creation story, all men should inherit the trait of missing one rib (although we are not clued in to whether it was just one rib or one pair). This part of the story might cause evangelicals to blush when it is realized that it is quite possible that the "rib" taken from Adam was not one of the bones in his chest at all, but rather a mythical baculum (or "penis bone"), which is present in most mammals but absent in humans and a few other species (Gilbert and Zevit 2001). The Bible is not a science book, though, and is generally opaque on the topic of anatomy. From the sun standing still in the sky (Joshua 10:13) to Jacob having the livestock in his charge mate in front of a striped pattern so that the animals would produce streaked and spotted offspring (Genesis 30:37-43), there are many stories in the Bible that directly run counter to what we've come to understand about the natural world. Still, we have come a long way since the time that the Genesis narrative was devised to account for our origins, evolution as we now know it being a relatively new idea that overturned previously held notions about our origins. Just as Homo sapiens has evolved, so too have our ideas about ourselves, and vestiges of past beliefs remain in the skeletal structure of our understanding.

From William Cheselden's Osteographia (1733).

Although the Genesis account of the creation of man is probably the most familiar, it is far from unique. The concepts found in the first chapters of the book of Genesis correlate surprisingly closely to older beliefs of the Chaldeans and Babylonians, from the differing orders of the two creation accounts to the dispersal at the Towel of Babel. Seeing that the myths from which the Genesis account derive no longer exist in their original form, however, we will start our intellectual foray with the set of beliefs that rails against science even to this day; that humans were specially created by God less than 10,000 years ago from little more than some dirt and a shard of bone. As alluded to previously, Genesis contains two separate creation narratives that contradict each other and cannot be reconciled (as many apologists attempt to do) by saying that the series of events described in Genesis 1 is merely an overview or outline, with Genesis 2 filling in the details.

In the Genesis 1 narrative, God creates plant life (before the "lights in the firmament"), then life in the water and the air, followed by all the "beasts" and "creeping things" (of which there are many more than the beasts), and finally both sexes of Homo sapiens simultaneously;

27: So God created man in his own image, in the image of God created he him; male and female created he them.

[Genesis 1:27]

The God of Genesis 2 does things a little differently (perhaps even taking a more pragmatic approach). We are told that because there was "no man to till the ground," there was no point in creating plants on earth before people. Thus God watered the entire face of the earth and then created man, "planting" the Adam in Eden. God then populates the Garden with plant life (which in Genesis 1 was long established on earth before Adam came to be), and then decides that it isn't good to have Adam wandering around Eden by himself. God then created all the "beasts of the field" and "fowl of the air" and had Adam name them (but neglected to form a proper system of taxonomy or systematics), but no "help mate" was to be found among the assemblage. Then comes the famous rib-story and things are finally set right in Eden, at least until the whole forbidden-fruit business. Despite the strange inconsistencies humans are the crowning achievements of the Creation in both accounts, told to "subdue" the planet and to reproduce in order to fill it. This idea of trampling nature beneath our heel has resonated with people for thousands of years, but perhaps more insidious has been the habit of some people to twist certain parts of Genesis this way and that to serve some rather horrific agendas.

Indeed, while Adam and Eve were supposed to be the ancestors of all humanity, some groups of people were left out of the picture. Just like certain lower classes of people in other cultures were said to be formed from the "dirt of the body" of particular gods, denoting their inferior existence, people with darker skin were deemed to be bearing the "Mark of Cain" or to be "Sons of Ham," in either case allowing slavery to be justified for the sins of the progenitor of that line. Thankfully this view has now largely been abandoned, although vestiges of such superstitions remain today. Racism and the Biblical justifications for it is another complex issue however, and it is only mentioned here to elucidate the point that even in theology the supposed origins of man have not always been used for good or just ends.

During the 19th century, however, the overthrow of Genesis as a historically-accurate narrative came to a boiling point, and basic researches into ancient Egypt and other cultures began to show that the chronology determined by John Lightfoot, James Ussher, and others was far too short to be accurate. Still, our place as a special creation didn't start to be truly challenged until the remains of ancient peoples markedly different from ourselves began to be discovered and recognized as a different kind of human. This required the birth of paleontology as a science, for fossils exhumed from the ground by many cultures had long been thought to be evidence of gods, titans, giants, dragons, and monsters. The bizarre remains often ended up as curiosities or holy relics rather than the being recognized for what they truly were, and some of the most well known monsters of ancient mythology (like the Cyclops and the Griffin) were probably born from strange bones weathering out of the ground (see Mayor 2000). One such instance was recounted in Andrew D. White's massive A History of the Warfare of Science With Theology in Christendom;

In France, the learned Benedictine, Calmet, in his great works on the Bible, accepted ["the doctrine that fossils are the remains of animals drowned at the Flood"] as late as the beginning of the eighteenth century, believing the mastodon's bones exhibited by Mazurier to be those of King Teutobocus, and holding them valuable testimony to the existence of the giants mentioned in Scripture and of early inhabitants of the earth overwhelmed by the Flood.

Yet even as the science of paleontology grew during the first half of the 19th century, the remains of the ancient humans were conspicuously lacking. The famous British fossilist Gideon Mantell noted this strange phenomenon is the posthumously-published Medals of Creation;

But of MAN and his works not a vestige appears throughout the vast periods embraced in this review. Yet were any of the existing islands or continents to be engulphed in the depths of the ocean, and loaded with marine detritus, and in future ages be elevated above the waters, covered with consolidated mud and sand, how different would be the characters of those strata from any which have preceded them! Their most striking features would be the remains of Man, and the production of human art - the domes of his temples, the columns of his palaces, the arches of his stupendous bridges of iron and stone, the ruins of his towns and cities, and the durable remains of his earthly tenement imbedded in the rocks and strata - these would be the "Medals of Creation" of the Human Epoch, and transmit to the remotest periods of time a faithful record of the present condition of the surface of the earth, and of its inhabitants.

This doesn't mean that the remains of humans were not thought to have been discovered by this time, however. In an earlier chapter on reptiles (amphibians being included within the reptiles in scientific works of the time), Mantell writes;

A celebrated fossil of this class is the gigantic Salamander (Cryptobranchus), three feet in length found at Ceuingen, which a German physician of some note (Scheuchzer) supposed to be a fossil man!

Caption: Scheuchzer's tricky salamander (which he named Homo diluvii testis), known as Cryptobranchus scheuchzeri today.

Despite such occasional misidentifications, the efforts of Mantell and others allowed naturalists to realize that the remains of animals coming out of sites like the Blue Lias of England (i.e. plesiosaurs and ichthyosaurs) and the Wealden pits (i.e. Iguanodon and Hylaeosaurus) represented an ancient fauna that did not have any living counterpart. These creatures obviously lived and died in a time before humans, for how could our own frail species survive sharing the landscape with monsters like Megalosaurus? Antediluvian worlds or early (somehow flawed) creations were thought up by theologians to reconcile the problem, A.D. White quoting from Dr. Anton Westermeyer's The Old Testament vindicated from Modern Infidel Objections to illustrate this point;

"By the fructifying brooding of the Divine Spirit on the waters of the deep, creative forces began to stir; the devils who inhabited the primeval darkness and considered it their own abode saw that they were to be driven from their possessions, or at least that their place of habitation was to be contracted, and they therefore tried to frustrate God's plan of creation and exert all that remained to them of might and power to hinder or at least, to mar the new creation." So came into being "the horrible and destructive monsters, these caricatures and distortions of creation," of which we have fossil remains. Dr. Westermeyer goes on to insist that "whole generations called into existence by God succumbed to the corruption of the devil, and for that reason had to be destroyed"; and that "in the work of the six days of God caused the devil to feel his power in all earnest, and made Satan's enterprise appear miserable and vain."

The fossil labeled "Scrotum humanum" by Robert Plot. Traditionally the fossil has been thought to have been part of the femur of Megalosaurus but it is impossible to determine its exact affinities, and Plot's label does not constitute a true binomial name (thus we can't start calling Megalosaurus "Scrotum").

Although the first known remains of a theropod dinosaur were presumed to be the enormous testicles of an "Antediluvian Giant" by some, the skeletal remains of Megalosaurus found by William Buckland (and those of Iguanodon found by Mantell) showed that these animals did not fit into Genesis under a narrow, literal reading. While evolution or "transmutation" of species was not yet ready to make its full appearance on the scientific stage, the scientific identification of fossils and revolutions in geology brought about by James Hutton, Charles Lyell, William Smith, Nicolas Steno (who developed the idea of superposition in geology in the 17th century), and others paved the way for the idea of evolution. The concept of extinction that Georges Cuvier did so much to establish also became essential to scientific thought and was a great victory over the religious dogma that God would not create a kind of animal and then let it be destroyed. Even in the light of such intellectual progress, however, there were some who preferred to cling tightly to religious texts rather than rethinking their beliefs when confronted with the mounting evidence for a dynamic and changing world much older than had previously been imagined.

Despite his contributions to marine biology, Philip Henry Gosse published one of the most infamous attempts to reconcile the evidence from paleontology and geology with a historically-accurate Genesis account in his 1857 book Omphalos: An Attempt to Untie the Geological Knot. Taking the reader on a painfully protracted tour of creation, the author introduces us to Adam, the prose suggesting that Gosse has persuaded Adam to sit down for a full anatomical evaluation. After detailing certain aspects of Adam's body (including the ever-problematic navel from which the book gained its title), Gosse tells us that every bit of Adam's anatomy tells of a full human life, from gestation to birth to growth, but this is merely a set-up for Gosse's theological punch-line that the world was created with the illusion of great age. Gosse writes;

How is it possible to avoid this conclusion? Has not the physiologist irrefragable grounds for it, founded on universal experience? Has not observation abundantly shown, that, wherever the bones, flesh, blood, teeth, nails, hair of man exist, the aggregate body has passed through stages exactly correspondant to those alluded to above, and has originated in the uterus of a mother, it foetal life being, so to speak, a budding out of hers? Has the combined experience of mankind ever seen a solitary exception to this law? How, then, can we refuse the concession that, in the individual before us, in whom we find all the phenomena that we are accustomed to associate with adult Man, repeated in the most exact verisimilitude, without a single flaw-how, I say, can we hesitate to assert that such was his origin too?

And yet, in order to assert it, we must be prepared to adopt the old Pagan doctrine of the eternity of matter; ex nihilo nihil fit. But those with whom I argue are precluded from this, by my first Postulate.

Gosse's first Postulate being;

If any geologist take the position of the necessary eternity of matter, dispensing with a Creator, on the old ground, ex nihilo nihil fit, - I do not argue with him. I assume that at some period or other in past eternity there existed nothing but the Eternal God, and that He called the universe into being out of nothing.

Strangely, the works of Gosse, Mantell, and others make no mention of the fact that remains of ancient hominids had been discovered in the first half of the 19th century. While the most noted discovery of the hominids known to us as Neanderthals occurred 151 years ago, Neanderthal fossils were found as early as 1829, and it can be presumed that the remains of ancient humans were stumbled upon even earlier. The problem was that many of the discoveries were of relatively recent hominids in Europe and so represented hominids close to us, even T.H. Huxley ascribing Neanderthal remains to being within the range of human variation within in his book Evidence as to Man's Place in Nature. The remains of Neanderthals and stone tools seemed to be too close to Homo sapiens to dissuade advocates of special creation that man had evolved, although scientists were able to confirm that the origins of mankind were probably far older than anyone had previously thought.

While it was preceded by works like Robert Chambers' Vestiges of the Natural History of Creation, a popular book that got the public talking about evolution, the publication of Charles Darwin's On the Origin of Species by Natural Selection made evolution a scientifically credible and defensible idea. Human evolution was what was on everyone's mind whether Darwin mentioned it or not, however, and even though he generally avoided the evolution of humans in On the Origin of Species by Natural Selection he later confronted the issue directly in The Descent of Man.

Man may be excused for feeling some pride at having risen, though not through his own exertions, to the very summit of the organic scale; and the fact of his having thus risen, instead of having been aboriginally placed there, may give him hope for a still higher destiny in the distant future. But we are not here concerned with hopes or fears, only with the truth as far as our reason permits us to discover it; and I have given the evidence to the best of my ability. We must, however, acknowledge, as it seems to me, that man with all his noble qualities, with sympathy which feels for the most debased, with benevolence which extends not only to other men but to the humblest living creature, with his god-like intellect which has penetrated into the movements and constitution of the solar system - with all these exalted powers - Man still bears in his bodily frame the indelible stamp of his lowly origin.

Darwin wasn't the first to consider that humans had changed in form over time, although he was much closer to the truth than many of his predecessors (and therefore we should be careful in identifying the views of earlier naturalists and philosophers as being true precursors of evolution [see Bowler 2007]). The Ionic philosopher Anaximander, for instance, proposed that humans had their recent origins in the sea (and this basic idea would later make a return, in new form, as the Aquatic Ape Hypothesis). In his summation of "evolutionary" thought, From the Greeks to Darwin, Henry Fairfield Osborn presents Anaximander's thesis this way;

He conceived of the earth as first existing in a fluid state. From its gradual drying up all living creatures were produced, beginning with men. These aquatic men first appeared in the form of fishes in the water, and they emerged from this element only after they had progressed so far as to be able to further develop and sustain themselves upon land. This is rather analogous development from a simpler to a more advanced structure by a change of organs, yet a germ of the Evolution idea is found here.

We find that Anaximander advanced some reasons for this view. He pointed to a man's long helplessness after birth as one of the proofs that he cannot be in his original condition. His hypothetical ancestors of man were supposed to be first encased in horny capsules, floating and feeding in water; as soon as these 'fish-men' were in a condition to emerge, they came on land, the capsule burst, and they took their human form.

There were many thinkers who also proposed that life could change form over time, but the evolution of life on earth did not fully command the respect of scientists until Darwin and Wallace presented natural selection as a primary mechanism of evolutionary change (although Wallace eventually fell into a sort of spiritualism that undercut his evolutionary work). Once evolution could be duly considered in scientific circles, a more rigorous search for our own ancestors could begin. Still, although Darwin had made evolution intellectually viable this did not mean that everyone agreed on natural selection as a primary mechanism (even Huxley, "Darwin's Bulldog," disagreed on this point), and it was not until the Modern Synthesis of the mid-20th century that natural selection was successfully married to new data from genetics, paleontology, and population biology to the exclusion of other mechanisms like those of Neo-Lamarckism. Part of the allure of Neo-Lamarckism was that it seemed to be a more positive force, organisms improving themselves through their own efforts rather than being culled in what was envisioned as a wholly destructive process of natural selection, and the ease with which some could reconcile Christian theology with the Neo-Lamarckian view provided natural selection with some competition for a time. One Neo-Lamarckian researcher was the well-known (if not infamous) American paleontologist E.D. Cope, and in his1896 treatise The Primary Factors of Organic Evolution he supported one of Ernst Haeckel's hypotheses for the origin of humans;

I have advanced the hypothesis that the Anthropomorpha (which includes man and the anthropoid apes) have been derived directly from the lemurs, without passing through the monkeys proper. This close association of man with the apes, is based on various considerations.

Cope goes on to list some of the differences, focusing primarily on limbs and teeth, before coming to this passage (also note the inferred racism, where various populations of people are considered to represent "approximations to the simian type");

Professor Virchow in a late address has thrown down the gage to the evolutionary anthropologists by asserting that "scientific anthropology begins with living races," adding "that the first step in the construction of the doctrine of transformism will be the explanation of the way the human races have been formed," etc. But the only way of solving the latter problem will be by the discovery of the ancestral races, which are extinct. The ad captandum remarks of the learned professor as to deriving an Aryan from a Negro, etc. remind one of the criticisms directed at the doctrine of evolution when it was first presented to the public, as to a horse never producing a cow, etc. It is well known to Professor Virchow that human races present greater or less approximations to the simian type in various respects... Professor Virchow states that the Neanderthal man is a diseased subject, but the disease has evidently not destroyed his race characters; and in his address he ignores the important and well-authenticated discovery of the man and woman of Spy. These observations are reinforced by recent discovery of a similar man by DuBois at Trinil in the island of Java ["Java Man," known today as Homo erectus].

Cope then goes on to describe the fossils, explaining that the remains Eugene DuBois had found in Java did not seem to be of a Neanderthal. In fact, Neanderthals were sufficiently far from humans in Cope's view that he found the scientific name Homo neanderthalensis objectionable, the more defining characteristics of Neanderthals being found nowhere in the aboriginal peoples then known and therefore placing Neanderthals further away from our own line. Despite the fact that Cope had more to work with when discussing human evolution in terms of fossils and hypotheses of other researchers, the fossil remains of hominids (and in turn, their ancestors) were still exceedingly rare during his time. By the first half of the 20th century, however, some scientists began to come across some fantastic fossil finds in southern Africa. Raymond Dart was one of these scientists (vertebrate paleontologist Robert Broom being drawn to study in this area and continue the work Dart started), and his research centered upon the great fossil-bearing caves of Sterkfontein and Makapansgat in South Africa, the first focus of his study being the famed fossil child from Taung. The hominids Dart was finding were far older than the Neanderthals of Europe or even of Homo erectus in Asia, and Dart named the species Australopithecus africanus, meaning "Southern Ape of Africa." In his invaluable work The Hunters of the Hunted?, C.K. Brain shares this passage written by Dart interpreting what A. africanus might have been like based upon the masses of damaged bone surrounding the hominid fossils;

The fossil animals slain by the man-apes at Makapansgat were so big that in 1925 I was misled into believing that only human beings of advanced intelligence could have been responsible for such manlike hunting work as the bones revealed... These Makapansgat protomen, like Nimrod long after them, were mighty hunters.

They were also callous and brutal. The most shocking specimen was the fractured lower jaw of a 12-year-old son of a manlike ape. The lad had been killed by a violent blow delivered with calculated accuracy on the point of the chin, either by a smashing fist or a club. The bludgeon blow was so vicious that it had shattered the jaw on both sides of the face and knocked out all the front teeth. That dramatic specimen impelled me in 1948 and the seven years following to study further their murderous and cannibalistic way of life.

Such was the murderous Australopithecus of R. A. Dart; a brutal savage and cannibal that made tools and weapons out of the bones and horns of the animals that were killed (known as the "osteodontokeratic culture"). Examinations of the cave after Dart, however, revealed something incredibly different from the terrifying reign of the "protomen"; the mighty hunters were the prey. Many remains attributed to cannibalism instead showed signs that the hominids were preyed upon by leopards (one particular skull bearing two punctures that exactly match the placement of canines in the lower jaw of a leopard) and that their bones were further modified after death by the gnawing of scavengers and porcupines. Indeed, the bones that were washed into the caves to create the jumbled assemblages show no sign of the domination of Australopithecus over the landscape. Rather than being mighty hunters, A. africanus may have scavenged from the kills of leopards and incorporated some fresh meat into the diet by taking small prey like bushbuck, and Dart's view eventually could not stand up to the contrary evidence. These details have only recently become known, however, and there were plenty of other ideas about our ancestors circling in both scientific and popular circuits prior to 1950.

Despite the progress of science there have always been fringe hypotheses about humans and their place in the universe, and perhaps nothing fueled crackpot claims so much as the popularity of UFOs and aliens during the first half of the 20th century. Rather than evolving over millions of years here on earth, our species became the product of alien engineering projects, the fruit of unions between aliens and early hominids, or even an alien race with no remembrance of coming from a civilization on another planet. Racist hypotheses also abounded, and there were many odd amalgamations of cherry-picked scientific discoveries and superstition. Unfortunately, some of the "spacey" ideas about our origins still hold on to this day even though they gained prominence by being advocated by amateurs appealing to the public without analysis or review by scientists (the works of Erich Anton Paul von Däniken being among the most famous). Even in the scientific realm, though, there were ideas that had more to do with racism and strange evolutionary mechanisms, many of the eventually discarded notions having to do with orthogenesis, vitalism, and species senescence.

While some were content to conjure up ideas of aliens laying down with hominids many scientists continued their attempts to determine not only from what ancestors humans arose from but where the remains of those ancestors might be found. A.S. Romer, in the 1933 book Man and the Vertebrates Vol. I, supports H.F. Osborn's view that the ancestors of humanity were likely to be found somewhere in Asia. Indeed, the famous 1923 expedition to the Flaming Cliffs of Mongolia by Roy Chapman Andrews that yielded Protoceratops and so many dinosaur eggs was originally intended to be a search for the ancestors of humans (the discovery of "Peking Man" [Homo erectus] in China supposedly supporting this view). Romer writes;

The fossil of Tertiary tropical life is, however, still comparatively unknown. It is not only possible but extremely probable that the Asiatic hills will, upon further exploration, give us the certain knowledge we desire of the primate ancestors of man.

Despite the lack of early ancestors, however, there was enough scientific understanding for Romer to close out the 1st volume with the following words;

Man has gone far and, we trust, may go still farther along the lines of evolution. But in his every feature - brain, sense organs, limbs - he is a product of primitive evolutionary trends and owes, in his high estate, much to his arboreal ancestry, to features developed by his Tertiary forefathers for life in the trees.

Romer's illustration of human evolution varies from the process envisioned by Cope at the turn-of-the-century. While Cope saw humans evolving directly from lemur-like ancestors, Romer created a diagram of extant primates (lemurs, tarsiers, new world monkeys, old world monkeys, great apes, and man) connected by one line, each of the groups branching off from the main line leading to man. This is part of the classic model of progressive evolution that seems to suggest non-stop progress to the human form, almost as if a vitalistic force was setting humans on a fast-track (although I am not suggesting Romer had this view or advocated it; it merely seems to be an underlying theme in such illustrations). As G.G Simpson noted in his 1949 popular-audience book The Meaning of Evolution, however, the study of creatures so close to humans can easily lead to contention;

Primate classification has been the diversion of so many students unfamiliar with the classification of other animals that it is, frankly, a mess. It involves matter of opinion on human origins and, humans being what they are, such opinions are endlessly varied and not always distinguished by competence or logic.

Simpson's diagram of primate evolution is a bit closer to truth than Romer's, as well. It more closely resembles the "branching bush" of evolution, groups linked by common ancestors with some lineages dying out and leaving no living descendants. Edwin H. Colbert (another vertebrate paleontologist at the American Museum of Natural History), put forth a similar view in his popular work Evolution of the Vertebrates, stating;

Even though human beings may not be descended from the australopithecines as we know them, it is very possible that man arose from australopithecine-like ancestors. The origin of the human stock probably occurred in late Tertiary times, for man is essentially a Pleistocene animal. Having become differentiated from his primate relatives, man evolved during the Pleistocene period along certain lines that made him what his is today. The evolutionary development of human beings was not of great magnitude within the course of Pleistocene history; rather it was a matter of the perfection of details that set man apart from all other primates, and from all other animals for that matter.

While this passage is somewhat vague, Colbert at least does not line up the known fossil hominids into a straight line from Australopithecus to Homo sapiens. Some of the pictures accompanying his text, however, do suggest a sort of progressive evolution from Australopithecus to Homo erectus to Neanderthals to Homo sapiens, the effect of an image sometimes being more powerful than what is found in the text. Chris Beard, in his book The Hunt For the Dawn Monkey, attributes the overall view of human evolutionary "progress" to W.E. Le Gros Clark, quoting Clark's work The Antecedents of Man;

Among the Primates of today, the series tree shrew-lemur-tarsier-monkey-ape-man suggests progressive levels of organization in an actual evolutionary sequence. And that such a sequence did occur is demonstrated by the fossil series beginning with the early plesiadapids [so-called "archaic primates" from the Paleocene] and extending through the Palaeocene and Eocene prosimians, and through the cercopithecoid [Old World monkeys] and pongid [apes] Primates of the Oligocene, Miocene, and Pliocene, to the hominids of the Pleistocene. Thus the foundations of evolutionary development which finally culminated in our own species, Homo sapiens, were laid when the first little tree shrew-like creatures advanced beyond the level of the lowly insectivores which lived during the Cretaceous period and embarked on an arboreal career without the restrictions and limitations imposed by... a terrestrial mode of life.

Most of the hominid fossils known when le Gros Clark wrote his book were almost like bookends to a series, with the lemur-like early forms (i.e. Notharctus from North America and Adapis from France) and the famous African and European hominids being the most well known. Given the amount of gaps in the middle (many of which still exist), anthropologists often had to look to living primates for clues as to what to expect from the fossil record. This does not mean that anthropologists thought that we evolved from any living ape, though, and earlier in the same book (The Antecedents of Man) le Gros Clark explains;

It is not to be inferred, of course, that man has actually been derived from an anthropoid ape of the specialized type which exists to-day, or that a monkey ever developed from a modern sort of lemur. The various members of the living Primates are all the terminal products of so many divergent lines of evolution; they are not in any way to be taken to represent a linear sequence of evolution. What a series of this kind does indicate is that, even without reference to paleontological evidence, there are connecting links of an approximate kind between Homo sapiens and small mammals of quite a primitive type...

As countries became more open to paleontological expeditions, however, more and more fossils came out of the ground, and Beard notes that while Africa may very well be the "cradle of humanity" in terms of hominids, if you really want to go back to the beginnings of human evolution to prosimians Asia is the place to search. This somewhat vindicates those who thought that Asia would be the place to look for human ancestors, though not quite in the way they imagined. Even so, the ladder view of tree shrew-lemur-tarsier-monkey-ape-man remained entrenched, fossil hominids being slotted into their own ladder as more fossils close to our own species were discovered. In his Vertebrate Paleontology (3rd Edition), A.S. Romer wrote;

A word may be added here with regard to the nomeclature of human finds. We have freely used several generic terms for various early human finds. Such a usage implies that the forms differed widely from one another, had independent evolutionary histories, and did not interbreed - that the differences between them were not merely of species value but of such a magnitude as, for example, those between a cow and an antelope, a dog and a fox. This is absurd. Because they are so close to us, we tend to magnify differences. Actually, the differences between modern man and "Pithecanthropus" [Homo erectus] are, viewed impersonally, rather minor ones (particularly if we keep in mind the considerable variations found even today), and quite surely all types on the human line above the Australopithecus level pertain to our own genus Homo. Further, while communications between the various Old World areas in which man was early present were obviously poor, and there presumably was little interbreeding and consequently (as today) a tendency for the differentiation of regional races, it seems fair to assume that throughout our long Pleistocene history, our human ancestors formed at all stages a single, if variable, group.

Despite this rather homogenous view of human evolution (the idea that Homo erectus falls within human variation recalling earlier ideas than Neanderthals were simply diseased members of Homo sapiens), Romer does make a distinction when it comes to Neanderthals. He writes;

A type of man definitely assignable to our own species, Homo sapiens, appeared in Europe well toward the end of the last glaciation, not more than 50,000 years or so ago. One would at first assume that he had arisen from his Neanderthal predecessor. But the contrasts are too great; there in (in Europe, at least) no evidence of transitional types; the appearance of modern man was, the evidence suggests, relatively sudden. There is every indication that the "modernized" invaders wiped out their predecessors (Tasmania is a modern parallel).

There is more to the development of ideas surrounding human evolution than lines of descent, however. Carrying on the tradition of Dart's killer man-apes, early humans were often portrayed as violent hunters, the killing of game and consumption of meat seemingly explaining almost anything about what we thought made us unique. In turn, ancient bloodlust was used to explain the darker parts of ourselves that we found undesirable, our species having comes so far so fast due to culture that our instincts have not yet caught up. In 1966, ethologist Konrad Lorenz wrote in On Aggression;

Obviously, instinctive behavior mechanisms failed to cope with the new circumstances which culture unavoidably produced even at its very dawn. There is evidence that the first inventors of pebble tools, the African Australopithecines, promptly used their new weapon to kill not only game, but fellow members of their species as well. Peking Man, the Prometheus who learned to preserve fire, used it to roast his brothers; beside the first traces of the regular use of fire lie the mutilated and roasted bones of [Homo] erectus himself.

The 1960's also saw the arrival of a symposium book called Man the Hunter that attempted to tie together various lines of evidence to help reconstruct the habits of our ancestors. While the editors of the collection defined hunting more broadly than the acquisition of vertebrate flesh and noted the importance of plant foods to human diets, the book is most often associated with a male-centered reconstruction of human evolution that put too much emphasis on hunting (the book even inspiring counter-collections like 1981's Woman the Gatherer). While scientific ideas surrounding "Man the Hunter" and the savanna hypothesis for human evolution took time to modify and root out, some people were already looking for another narrative to explain what appeared to be unique about our own species. Centuries after Anaximander proposed his own views on the aquatic nature of man, Alister Hardy presented a lecture on "Aquatic Man: Past, Present, and Future" in 1960, and soon afterwards he presented the idea to the public in a series of articles for New Scientist magazine. Although largely forgotten today, this lecture was to become the springboard for the development of one of the strangest evolutionary narratives every proposed; the aquatic ape hypothesis.

For a time after the aquatic ape hypothesis was presented by Hardy, few took notice of it. Desmond Morris, in his popular but off-base book The Naked Ape, did briefly mention the hypothesis, however;

Another, more ingenious theory is that, before he became a hunting ape, the original ground ape that had left the forests went through a long phase as an aquatic ape. He is envisaged as moving to the tropical sea-shores in search of food. There he will have found shellfish and other sea-shore creatures in comparative abundance, a food supply much richer and more attractive than that on the open plains. At first he will have groped around in the rock pools and the shallow water, but gradually he will have started to swim out to greater depths and dive for food. During this process, it is argued, he will have lost his hair like other mammals that have returned to the sea. Only his head, protruding from the surface of the water, would retain the hairy coat to protect him from the direct glare of the sun. Then, later on, when his tools (originally developed for cracking open shells) became sufficiently advanced, he will have spread away from the cradle of the sea-shore and out into the open land spaces as an emerging hunter.
...
Unfortunately, [searching for fossils in marine or fluvial deposits or further research into the AAH] has yet to be done and, despite its most appealing indirect evidence, the aquatic theory lacks solid support. It neatly accounts for a number of special features, but it demands in exchange the acceptance of a hypothetical major evolutionary phase for which there is no direct evidence. (Even if eventually it does turn out to be true, it will not clash seriously with the general picture of the hunting ape's evolution out of a ground ape. It will simply mean that the ground ape went through a rather salutary christening ceremony.)

As short and tentative as this treatment may be, it was enough to gain the interest of a woman named Elaine Morgan, and in 1970 she wrote Hardy about furthering the aquatic ape hypothesis. The book The Descent of Woman was the result, but rather than providing a scientific alternative to a bloodied hominid struggling for life out on the African savanna Morgan's apes went off the deep end, her ideas forming as an objection to the focus on males in anthropological studies of the time. In a passage describing her own image of Australopithecus, Morgan plays loose with anthropological reconstruction to turn a female hominid into a kind of fertility goddess;

So our hominid has a nose. I have no doubt that she also had fleshy nostrils, but considerable doubt that they evolved to make sex sexier for her mate. I think she was by no means the simian, cadaverous, lipless creature that artists sometimes reconstruct by covering her dug-up skull with a tightly fitting layer of hairy skin. The layer of fat which was rounding out her arms and legs and adding bulk to her breasts was also filling out her cheeks, and her nostrils, and her earlobes, and everting her lips... We would not have accounted her beautiful, with her low forehead and prognathous jaw, but the chances are that she was a chubby little creature with several superficial features resembling our own more nearly than they resembled any ape's. And as for the expressions that flitted across that prehistoric countenance, her millions of years in the water had certainly left their mark on those also.

All of this "beauty," Morgan contends, was due to a life swimming in the water rather than moving through the African forest and woodlands, the motivation for her recreation of the female hominid becoming clear in the last words of the book where the brutish males are invited into the sacred waters the females know so well;

He is the most miraculous of all the creatures that God ever made or the earth ever spawned. All we need to do is hold out our loving arms to him and say: "Come on in, the water's lovely."

Morgan wrote other books on the subject and there still is a bit of a following to the idea that humans arrived in their current configuration due to an "aquatic stage" sometime in their history. Long hair on the head is for babies to cling to, large breasts float better than small ones, hairlessness makes one more streamlined, and nearly any part of the body is potentially explained by life in or around the water, and thus the hypothesis succumbs to some of the same conceptual pitfalls that spurred Morgan to reject the "Man the Hunter" image in the first place. Despite many of the post hoc rationalizations, however, some recent popular science books (as well as noted philosopher Daniel Dennett) have taken a bit of a shine to the aquatic ape hypothesis, but no hard evidence in support of the idea has floated to the surface.

As wrong as it might have been, the rise of the aquatic ape hypothesis showed that things were certainly set for change, the ladder-like progression of the mighty hunter looking more and more flimsy. Despite the move away from old notions of human evolution that were spreading in the 1970's, the decade would mark the arrival of one of the most infamous illustrations of human evolution ever produced. Like it or not, visual representations of abstract concepts often stay with us longer than written explanation, and the erroneous "March of Progress" has long overstayed its welcome. The illustration, appearing in the 1979 Time-Life book Early Man by F. Clark Howell, certainly has become iconic, although this is a rather dubious distinction. The "March," with all members standing upright, carries this caption;

The stages in man's development from an apelike ancestor to the modern human being are shown in drawings on this and the following three pages. Some of the stages have been drawn on the basis of very little evidence - a few teeth, a jaw or some leg bones. However, experts can often figure out a great deal about what a whole animal looked like from studying these few remains. In general, man's ancestors have grown taller as they became more advanced. For purposes of comparison, this chart shows all of them standing although the ones on this page [Pliopithecus through Oreopithecus] actually walked on all fours.

(The "March" proceeds as follows: Pliopithecus - Proconsul - Dryopithecus - Oreopithecus - Ramapithecus - Australopithecus africanus - Australopithecus robustus - Australopithecus boisei - Homo habilis - Homo erectus - Early Homo sapiens - Neanderthal Man - Cro-Magnon Man - Modern Man)

The image is instantly familiar; a monkey-like animal standing up on its hind legs transitions into stooped-over "ape men," some of which carry tools of stone or wood, culminating the an upright and proud representative of Homo sapiens. The inclusion of "Early Homo sapiens" before "Neanderthal Man" is a strange one for an image that appears to promote a ladder of human progress, though, and even on the following pages of the book australopithecines are shown living during the same time or exhibiting stark differences between species. Surely, it was known that the "robust" Australopithecus boisei was on a different evolutionary line than Australopithecus africanus and did not give rise to Homo erectus, as well, the text thus being essential to deciphering what is actually being shown in the illustration. Yet while the author and artists of the book may not have meant to show that all the representatives in the illustration evolved directly from their predecessors in a straight line, the power of the image overwhelmed any explanation in the text, and the picture has certainly become entrenched in popular culture. Evolutionary biologists did not sit idly by while a fallacious notion of human evolution was promulgated, however; Stephen Jay Gould opens his 1989 book on the Cambrian fauna Wonderful Life with a firm refutation of the "March";

The march of progress is the canonical representation of evolution - the one picture immediately grasped and viscerally understood by all. This may best be appreciated by its prominent use in humor and in advertising. These professions provide our best test of public perceptions. Jokes and ads most click in the fleeting second that our attention grants them. ...

Life is a copiously branching bush, continually pruned by the grim reaper of extinction, not a ladder of predictable progress. Most people may know this as a phrase to be uttered, but not as a concept brought into the deep interior of understanding. Hence we continually make errors inspired by unconscious allegiance to the ladder of progress, even when we explicitly deny such a superannuated view of life. ...

First, in an error that I call "life's little joke", we are virtually compelled to the stunning mistake of citing unsuccessful lineages as classic "textbook cases" of "evolution." We do this because we try to extract a single line of advance from the true topology of copious branching. In this misguided effort, we are inevitably drawn to bushes so near the brink of total annihilation that they retain only one surviving twig. We then view this twig as the acme of upward achievement, rather than the probable last gasp of richer ancestry.

Gould is right to be aggravated by the recycling of the illustration; the iconic imagery of the "March" is so wrong, yet so easily understood, that it survives despite its inaccuracy. Creationists use it as a symbol of evolution (or, more often, mistakes evolutionary scientists have made), while satirists often use it to show the "devolution" of one group or another, and I doubt that the image will lose its utility anytime soon. If nothing else, the lesson we must learn from "The March of Progress" is that we are to use the utmost care in selecting visual representations of evolution, for one image can stay in the collective understanding (or misunderstanding) of a subject even when it's accuracy has long passed the expiration date.

Although it has clearly always been vibrant, the study of human evolution became even more so between the 1970's and the present. Numerous fossil discoveries, long-term fieldwork involving wild apes, laboratory research on primate cognition, and sundry other lines of evidence have become increasingly important to understanding our own evolution. The evolution of Homo sapiens from earlier hominids is certainly well-established, the course of evolution revealing that (to borrow Gould's metaphor) we are but a single twig on a bush that once held a much wider diversity of hominids. So many unexpected finds have come out of the ground that imagining human evolution to be a straight-line teleological process, finely-tuned to produce us in our present form, is utterly ridiculous. There are still battles to be fought over which fossil fits where, the timing and details of the hominid dispersal from Africa, what evolutionary factors led to our ancestors being obligate bipeds, etc., but the competing hypotheses in such debates become more and more refined with every discovery. The evidence supporting the fact that we have evolved cannot be overturned. Still, there is always room for debate and controversy. One of the major debates at present centers around the fossils that may represent the earliest fossil hominids, Ardipithecus kadabba (which some consider to be on the chimpanzee side of the split), Orrorin tugenensis, and Sahelanthropus tchadensis (the current favorite candidate), all being proposed as the "root" of our evolutionary bush. The debate will likely continue as more fossils are discovered, but modern anthropology is not based upon paleontology and morphology alone.

When fossil hominids were lacking, many of the diagrams of human evolution devised during the first half of the 20th century based themselves on living primates and prosimians, looking to living creatures for representative types that would approximate evolutionary transitions. There has been something of a return to this as of late, but in the area of our brains and behavior rather than morphology. Chimpanzees and bonobos, after being confirmed as our closest living relatives through study of genetics, are often used as the two polar archetypes for our own ancestry; we were either violent like chimpanzees, horny bohemians like bonobos, or something in-between. Such a close comparison can often prove disturbing to those who would rather not share the majority of their genetic code with an ape. In On Aggression, Konrad Lorenz suggests;

An inexorable law of perception prevents us from seeing in the ape, particularly in the chimpanzee, an animal like other animals, and makes us see in its face the human physiognomy. From this point of view, measured by human standards, the chimpanzee of course appears as something horrible, a diabolical caricature of ourselves. ...he is irresistibly funny and at the same time as common, as vulgar as no other animal but a debased human being can ever be.

Primatologist Frans de Waal would later echo this sentiment in the introduction to his Chimpanzee Politics;

Visitors at a zoo always seem amused by the sight of chimpanzees. No other animals attracts so much laughter. Why should this be? Are they really such clowns, or does their appearance make them ridiculous? It is almost certainly their looks that amuse us, because they need do little more than walk around or sit down to make us laugh. The hilarity is perhaps a camoflage for quite different feelings - a nervous reaction caused by the marked resemblance between humans and chimpanzees. It is said that apes hold up a mirror to us, but we seem to find it hard to remain serious when confronted with the image we see reflected.

Even in fiction, it seemed impossible to comment on apes and not draw comparisons with humans. In the 19th century novel The Gorilla Hunters, the hunter Ralph describes some of the behavior of his gorilla quarry that comes a little too close to home;

Occasionally, however, they rose and ran on their hind legs, in a stooping position.

When they did this I was particularly struck with their grotesque yet strong resemblance to man, and I do not think that I could at that time have prevailed upon myself to fire at them. I should have felt like a murderer.

Such comparisons are only skin-deep, however, and it was not until Jane Goodall carried out her long-term studies of chimpanzees at Gombe in Tanzania that the living apes began to truly encroach on territory that was thought to set humans apart from all other animals. The habit of the Gombe chimpanzees to "fish" for termites with modified twigs caused Louis Leaky to famously opine "Now we must redefine man, redefine tool, or accept chimpanzees as humans," when he learned of Goodall's discovery of the behavior, but more startling revelations were to come. When the Gombe population split, one group of chimpanzees killed the members of the other population one by one, a whole set of previously unobserved violent behaviors making the apes seem even more human than before. This "dark side" is most prominently displayed in the book Demonic Males by Dale Peterson and Richard Wrangham, in which the males of all living apes (including our own species) are deemed to be exceedingly violent. According to the authors, our own violent proclivities are our inheritance from our forebears;

...humans are cursed with demonic males. First, why demonic? In other words, why are human males given to vicious, lethal aggression? Thinking only of war, putting aside for the moment rape and battering and murder, the curse stems from our species' own special party-gang traits: coalitionary bonds among males, male dominion over an expandable territory, and variable party size. The combination of these traits means that killing a neighboring male is usually worthwhile, and can often be done safely.

Frans de Waal has often championed a different view, recognizing our proclivity towards violence but remaining optimistic about being able to move away from behavioral inclinations towards violent behavior. This is partly due to his preference of the still-mysterious bonobo as a better model for early human ancestors, and he outlines this perspective in his book Our Inner Ape;

That such a creature [as Homo sapiens] could have been produced through the elimination of unsuccessful genotypes is what lends the Darwinian view its power. If we avoid confusing this process with its products... we see one of the most internally conflicted animals ever to walk the earth. It is a capable of unbelievable destruction of both its environment and its own kind, yet at the same time it possesses wells of empathy and love deeper than ever seen before. Since this animal has gained dominance over all others, it's all the more important that it takes an honest look in the mirror, so that it knows both the archenemy it faces and the ally that stands ready to help it build a better world.

A female gorilla at the Bronx Zoo. Photo by author.

While chimpanzees and bonobos are well-established as our closest living relatives, we have proceeded on our own line of evolution for at least 5,000,000 years, evolving on a much different trajectory than our evolutionary "cousins." This is not an appeal to say that humans are so distinct that we should not look to living primates for answers about how we have come to be as we are now, but rather that we must also keep the long view of evolution properly in perspective. As W.E. le Gros Clark noted decades ago, we did not evolve from any living ape and living apes did not evolve from any living monkey, and the fact that the fossil record for living apes is essentially empty at present makes comparisons even more difficult. Indeed, if we were to exclusively use the behavior of living apes to work backwards to the behavior of our own ancestors we would be making the common error of saying that we "evolved from monkeys," such a blunder being one of the most common mistakes still made by people unfamiliar with how evolution works.

Despite the amount of resources marshaled in this review of the changing self-image of our species, this has hardly been an exhaustive study. Major fossil finds and various hypotheses have largely been left out in order to focus on the more abstract interpretations and ideas surrounding our own evolution, although fact and theory will continue to intertwine as we attempt to discover the secrets of our own past. Indeed, science does not crumble when taxa are reassigned or a new fossil shows up where it was not expected; such changes only further our understanding and demand a reassessment of the available data. Anything else would be dogmatic assent that would cripple rather than invigorate. If a hypothesis is shown to be false then that is one more thing that can be cast off, therefore pruning a dead branch from our understanding and letting new ideas close over the gap. Assembling a body of facts alone will not suffice; as Charles Darwin once wrote "How odd it is that anyone should not see that all observation must be for or against some view if it is to be of any service!" Some will continue to consider this a source of weakness, but as we are not gods the constant desire to improve our understanding of nature is the best that we can hope for. What would be the alternative? To hold on to favored ideas even when they've been proven wrong, hoping that the mere devotion to a pet hypothesis would make it true in the fullness of time? Such an idea is far from being unproductive; it is dangerous and leads only from one dead-end to another.

The story of our own evolution is more enthralling and important than anything our own imaginations could have dreamed of, something incredibly vital and personal even if so many of the details are still beyond our grasp. It is for that reason that we should not feel embarrassment or shame when we realize that the monkey in the mirror is us; the long and tortured path our of history is written into our bones, into the very fabric of who and what we are, and it is our ability to recognize that which truly sets us apart.

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