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On Human Origins: A Survey.

John A. Bloom, Ph.D., Ph.D. Biola University

It is the theory which decides what we can observe. – Albert Einstein¹

Until about 150 years ago, the subject of human origins was almost exclusively the domain of religion. Revelation from the gods passed down through cultural tradition told man how he came to be and about his place in the Universe. Since the time of Darwin, however, material from the natural world itself has been discovered that allows the sciences to address the topic as well. Over the past forty years, intensive field work in Africa as well as striking advances in biochemistry have fostered a virtual explosion of new data which now must be incorporated into our models about origins.

Integrating a multidisciplinary database into a coherent, unified model is a difficult task. This becomes especially challenging when the issue involves our own origin, since here we cannot be neutral observers. The meaning and value which we assign to life are linked to the origins model we espouse. Since our significance depends on our pedigree, those who desire there to be no supreme authority over their lives will favor a different origins model than those who seek to glorify their divine Creator with their lives.

Unfortunately, most of the contact which nonspecialists have with human origins comes through the mass media, where a secular-humanistic bias seems to pervade the scientific content.[2] For the person who seeks to integrate this data with conservative Christian theology, it is difficult to judge from these sources which new discoveries are important and need to be incorporated into the synthesis, and which are but the artifacts of an overly zealous grant proposal or hidden personal agenda.

Because it touches closest to home, the controversy surrounding the creation / evolution debate becomes noisiest when the question of human origins is broached. Certainly if macroevolution[3] only concerned itself with bacteria, fish and rodents, its discussion would take place in the footnotes of biology journals; but since it ventures to offer a scientific opinion about who we are and what was involved in the process of getting us here, it commands the attention of society at large.

This occurs because the meaning and value that we assign to life are linked to our models for its origin: For example, some argue that we evolved by a meaningless collision of molecules and have no more significance than insects who hatch, eat, copulate and die; while others hold that we are a unique special creation formed to glorify God. Because we connect our significance with our pedigree, the following review of the physical data on human origins will include some consideration of its metaphysical fallout.

The goal of this article is to provide a neutral overview of some of the current data and issues in the human origins debate. Without getting buried by details, we will attempt to give the nonspecialist some feeling for the background to key scientific findings that bear on a conservative Christian reading of Genesis. After providing some historical background and outlining the relevant fossil and artifact evidence, we will consider some criticisms of this data. We will then review recent biochemical research and its contributions to this issue. Since space does not permit us to construct a fully integrated biblical-scientific model from the data, we will focus the discussion on only one apparent clash between the biblical and scientific models, that regarding the special creation of the first man. Our proposed resolution will serve as an example of the integrative tension and challenges that are present in this field today.

Historical Perspective.

The first major treatises to argue for human origins from a solely naturalistic outlook were T. H. Huxley’s Man’s Place in Nature (1863) and Charles Darwin’s The Descent of Man (1871). Although Neandertal[4] fossils had been recovered in Europe starting in 1856, they were considered to be irrelevant to the discussion because at that time their unique features were viewed as racial variation, not as non- or pre-human differences of evolutionary importance.[5] Thus Huxley’s and Darwin’s arguments hinged on man’s anatomical homology with modern apes and lower primates, not on any fossil data.

The quest for fossil evidence of a common ancestor for apes and man (popularly known as the “missing link”) was taken up by Eugène Dubois, a French anatomist who was inspired by the works of Ernst Haeckel. Haeckel, a leading German zoologist in the 1880’s and a strong proponent of macroevolution, proposed that the remains of “Ape-like Men” (to which he assigned the name Pithecanthropus) might be found on the continent of Lemuria [an ancient land mass proposed by nineteenth-century geologists that was believed to have sunk beneath the Indian Ocean]. Dubois took a medical position with the Dutch East India Army stationed in Java (then a colony of Holland) in order to be as close to the hypothetical homeland of the missing link as possible and proceeded to excavate in the fossil beds there.

After several years of work, Dubois had collected a primitive skull cap, tooth, femur (thigh bone), and several other bone fragments. The small brain size evidenced by the skull cap coupled with the modern appearance of the femur led him to the conclusion that he had found a transitional ape-like man that could walk upright; hence in 1893 he named his find Pithecanthropus erectus.[6]

Because the evidence was fragmentary and it was not certain that all of the bones came from a single individual, Dubois’ conclusion was not well received by most of the scientific community for many years.[7]

Unfortunately, Charles Dawson’s discovery of the Piltdown Man in 1913 did not meet with the same skepticism because the find’s combination of large brain size and ape-like jaw fit better with the preconceptions of the day.[8]

Meanwhile, interest in Asia picked up as other researchers found hominid fossils and tools in Zhoukoudian, China, and were proposing a missing link in the form of the “Peking Man.”[9]

In 1925 the search for early man turned to Africa (the homeland posited by Darwin because it was the habitat of the modern ape and chimpanzee) when Raymond Dart from South Africa reported the discovery of a fossilized skull of a very primitive young hominid, whom he named Australopithecus africanus (“southern ape from Africa”).[10]

Informally called the “Taung baby,” its relation to mankind was rejected[11] for over two decades, until Robert Broom[12] and others recovered many more australopithecine fossils. Early twentieth-century scientific models and preconceptions about human evolution then shifted to accommodate this mounting African evidence.

Louis Leakey faced the same pro-Asian bias when he began work in East Africa in 1931. Years of effort at the now famous Olduvai Gorge in Tanzania as well as sites in Kenya yielded the Zinjanthropus boisei or “Nutcracker Man” in 195913 and the first Homo habilis (“Handy Man”) fossil in 1961,[14] thus confirming the African-homeland hypothesis in many people’s minds.

Over the past forty years, the research efforts of paleoanthropologists have increased in both quantity and quality. It was estimated recently that we now have recovered the remains of at least 275 Neandertal individuals from more than 70 sites,[15] and the total number of known hominid fossil individuals exceeds six thousand.[16]

Consequently, rather than continuing to present these results in the order of their discovery, it is much more logical to summarize the material by the age of the fossil and its features.

Generally Accepted Hominid Categories.

Australopithecus afarensis

The most famous example of the species Australopithecus afarensis (“southern ape from Afar”) is called “Lucy,” discovered in 1974 by Donald Johanson at the Hadar Formation in Ethiopia.[17]

Although similar specimens were found later at other east African sites,[18] Lucy is unique because about 40% of her skeleton was recovered. Finding such a large fraction of bones from a single individual is striking, given the great age of the fossils (dated to about 3.2 million years ago [mya]).[19][20]

Standing between 3.5 to 5 feet tall, A. afarensis was thick-boned with proportionally shorter legs and longer arms than modern humans. From skeletal remains it was postulated that this species was fully bipedal, and the later discovery at Laetoli of a 3.7 million-year-old extensive track of hominid footprints made by three bipedal individuals[21] appears to bear out this hypothesis dramatically. Despite her advanced pelvis and mode of walking, Lucy’s skull is very similar to a chimp’s, with a small brain (400 cc average), and large teeth.[22]

Other Australopithecine species.

In the fall of 1994, the discovery of bone fragments from a more primitive australopithecine than A. afarensis was announced.[23] Called A. ramidus, these fossils are dated at 4.4 mya (over a million years older than Lucy), and should help show how the transition was made from early arboreal monkey-like primates to walking hominids.

Australopithecine hominids that appear in the record after Lucy are generally classed into at least three groups, A. africanus, A. boisei and A. robustus, based on their body size and cranial features. They have larger stature than afarensis, are also bipedal, and differ markedly from each other in their skull structure, probably due to the influence of diet.[24]

Since only africanus has dentition that is comparable with that found the later homo series, it is the only late australopithecine that some consider to be a direct ancestor to modern man.

Homo habilis

Homo habilis is the name given to a group of African fossils that are believed to have used the first primitive stone tools, called the Oldowan tradition.[25]

Spanning a time range from 2.3 to 1.5 mya, H. habilis was clearly bipedal, thin boned, and had a larger brain size (670 cc) than A. afarensis. One of the best H. habilis specimens is the nearly complete skull (KNM-ER-1470) found by Richard Leakey.[26]

However, recent new finds by Johanson (OH 62) suggest that H. habilis was not significantly taller than A. afarensis and had a similar short leg / long arm structure.[27]

This apparent mix of change and stability in H. habilis (a more human-like skull with a larger brain and smaller teeth than afarensis is still combined with an ape-like limb structure) makes it difficult to use in gradualist evolutionary schemes as a transitional species between A. afarensis and H. erectus. To remedy this problem, some suggest that this species should not be regarded as a human ancestor (i.e., a member of the genus Homo) but rather as a distinct evolutionary branch.[28]

Because there is considerable diversity in features among the specimens initially included in the H. habilis taxon, the current trend is to reassign the specimens into other better-known groups or divide them into more finely-specified taxa.[29] Thus Leakey’s KNM-ER-1470 specimen is reclassified as Homo rudolfensis.

H. habilis is the presumed occupant of the earliest known (dated to 1.8 mya) living area: This 2,400-square-foot site discovered by Mary Leakey at Olduvai Bed I contained over 4,000 artifacts and fossils. It provides direct evidence of simple windbreaks or shelters and suggests that early hominids had a nomadic hunter- gatherer lifestyle.[30]

Homo erectus

Homo erectus remains cover a period from 1.8 million to 300,000 years ago and are likely the first hominids to have a global (Old World) distribution. The most striking H. erectus find so far is undoubtedly Richard Leakey’s “Turkana Boy,” the nickname given to most of the skeleton of a large adolescent that dates to 1.6 mya (KNM-WT-15000).[31] As with habilus, the current trend with erectus specimens is to split them up rather than lump them into one taxon, so the Turkana Boy now is listed as an “early

African h. erectus” or h. ergaster. H. erectus manufactured the more advanced flaked stone tools of the Acheulian tradition, were involved in big-game hunting, and had the controlled use of fire. In many skeletal features they appear essentially modern.[32]

The largest differences occur in the skull, which is markedly flatter and thicker boned than modern humans. Moreover, the brow ridge above the eyes is very pronounced, the jawbone lacks a protruding chin, and the teeth are larger than moderns. The brain size of H. erectus appears to increase over time from 750 to 1,200 cc. Since a brain size of greater than about 800cc in a light-boned hominid places this species within the brain size range of modern man, some argue that H. erectus is the first true modern man.[33]

Others are hesitant to lump H. erectus with modern man solely on this criteria, noting that the Acheulian toolkit is comparatively simple and remained stable for over a million years, and thus does not reflect the innovation and creativity that characterize modern human artifacts.[34]

The global (old World) variation and migration patterns of the H. erectus family have been the focus of study in recent years. The distinctions between Asian erectus (old popular names being the “Peking” and “Java” man) and African erectus, combined with the very early date of some of the Asian fossils,[35] gave raise to speculations that these regional groups may have arisen from a much earlier migration than previously considered (i.e., an H. habilus migration instead of an H. erectus one), or that H. erectus actually evolved in Asia and migrated into Africa, a reversal of the dominant “out-of-Africa” theory. However, a new erectus find in Africa is of comparable date to the Asian fossils and shows a marked similarity to them, strengthening the single- species theory.[36]

Archaic Homo sapiens

Early (or archaic) Homo sapiens applies to a group of fossils that share a mixture of H. erectus and modern features [A recent trend in naming this group is to avoid the term “archaic” and to list them as Homo heidelbergensis (with variation)]. Most of these date from 300,000 to 100,000 years ago. In general the skeletal bones are less robust than H. erectus while the cranial capacity is larger, but the features are blurred enough that considerable debate surrounds their classification. Many scholars feel that there is essentially a continuum between late H. erectus and early Homo sapiens both in features and culture. For example, early Homo sapiens tools are basically of the Acheulian tradition, although some items (such as handaxes) apparently become less popular and we begin to see some refinements in toolmaking technique.[37]

Archaic Homo sapiens sites attest to a lifestyle of seasonal migration. A shore site at Terra Amata in France dated to about 300,000 years ago yielded large oval huts with a hearth at the center, large numbers of stone tools, and possible evidence for body decoration.[38] However, the date and significance of this site has been contested.[39]

Neandertals

Neandertals are noted separately from archaic Homo sapiens because of their historical fame and the ongoing debate regarding their classification. Their bodies, teeth and jaws are very robust by modern standards, and they share many of the cranial features found in H. erectus (above).

All of the Neandertal remains that have been recovered to date are restricted geographically to Western Europe and the Middle East. Their tools (called the Mousterian culture) are more sophisticated than H. erectus, although the evidence that they buried their dead is limited to two examples and remains controversial.[40]

Evidence of animal trapping as an alternative to hunting or scavenging is also found. Their first remains date back 80,000 years ago, and it appears that they were rapidly replaced by modern humans in Europe around 30,000 years ago, or that they died out before moderns immigrated into Europe.

The debate surrounding Neandertals involves their relationship to modern man, because the data are ambiguous even for secular minds: Is their culture sophisticated enough and anatomy compatible enough that they should be considered an intermediate step between H. erectus and modern man, or do they form a separate branch that has no recent ancestral relationship? Did Neandertals and modern humans occupy the same geographic areas at the same time or interbreed? The answer which secular scholars give to these questions depends heavily on the model for recent human prehistory which they assume (see below).

Anatomically modern humans

Anatomically modern humans (AMH), as the name implies, refers to hominid remains that are indistinguishable from modern man (allowing for some racial variation). They first appear in the fossil record at several sites in Africa that are dated between 125,000 to 100,000 years ago. The earliest remains have modern cranial features (high forehead, smaller teeth) but use the same tools as their archaic H. sapiens contemporaries.[41] Although there are some new tantalizing clues from Blombos cave in South Africa that AMH culture had elements of art and advanced tool-making skills over 70,000 years ago,[42] a distinct change occurs globally in the AMH record about 40,000 years ago, when culture that all researchers are comfortable in assigning to modern man suddenly appears around the world.[43]

We find ingenious weapons like boomerangs, an increased use of bone for tools, evidence of higher population densities than at previous times, of long distance migration to Australia and the New World, of trade or the transport of exotic materials over considerable distances, and – most strikingly – of artistic expression (sculpture, jewelry, painting, and music). In artistic expression, some see the first preserved clues to the religious interests of early man. David Lewis-Williams and Thomas Dowson propose that shamanistic experiences explain the unusual geometric shapes seen in wall paintings that date back as far as 27,000 BC.[44]

The origin of language, certainly an essential hallmark of modern man, is frustrating to evaluate since language leaves no clear trace in the archaeological record until the advent of writing (around 3,000 BC). Seeking secondary clues, researchers have investigated the physiology of fossil skulls for evidence of Broca’s and Wernicke’s areas (the two principal speech centers in the brain) and for evidence of the modern human larynx structure that allows a full variety of speech sounds to be produced. No consensus has been reached in these studies; some argue that H. habilis had Broca’s area[45] and thus could speak, and others argue that even the late Neandertal did not have our modern larynx and thus had a less efficient vocal repertoire.[46] Still other scholars note that just because an ancient hominid had the physical capacity for speech does not prove that any sophisticated language was in fact used. Working from the other direction, linguists have attempted to evaluate the rate at which modern languages develop and diverge over time so that some estimate back to a single original tongue can be made. Depending on the assumptions made, the evolution time for our present language diversity appears to be between 50,000 to 100,000 years, an age that seems linked to anatomically modern humans.[47]

III. Fossils: Summary and Appraisal.

If one imagines the above fossil and artifact data (cranial capacity, complexity of tools, date found in the fossil record, etc.) to form a series of points on a graph, the model of human origins which one espouses will affect how one draws the line connecting the points. Someone who believes that God intervened in the special creation of man will place at least one discontinuity somewhere on the graph, while someone who assumes that man shares a common ancestry with apes will arrange the data and connect the points so as to show a smooth transition from early primitive forms to late modern ones. The later scheme is the approach of secular naturalists and is shown in the figure below.

Prior to 1979, it was generally assumed that competition for limited resources permitted only one species to be the dominant hominid population in a region at a given time. However, fossil discoveries[48] since then showed that A. boisei existed in Africa as a contemporary with A. africanus, greatly weakening the argument that africanus was ancestral to robustus. In fact it appears that four or five distinct hominid species coexisted in Africa around two mya, making the evolutionary “tree” appear more like a bush during this period. The new discovery of ramidus as the earliest known hominid replaces afarensis at the trunk of the tree, and reopens the debate whether afarensis is really the last common ancestor to the australopithecine and homo lines, as Johanson proposed but Richard Leakey doubts.[49] The recent discovery of K platyops, a contemporary hominid with afarensis, raises the possibility that the “bushiness” seen at two mya extends all the way down, with the result that we cannot discern a single, unambiguous ancestral lineage nor an obvious “last common ancestor” with the primates.

A significant difficulty in evaluating the recent fossil data is that we are too close to the personalities and biases of the discoverers. Paleoanthropologists, being human, can be myopic about the overall significance of their own work: After all, everyone prefers to discover something new rather than find the seventeenth specimen of an already well-known species. Consequently it is often the next generation of scholars who are more objective at integrating data into a coherent scheme than the pioneers who made the original discoveries. Bearing this in mind, it is not unreasonable to find that scholars questioned the validity of a given species, such as H. habilis, and asked for a review of the specimens assigned to this taxon.[50] It is even possible this taxon may disappear because its fossils can be better assigned (on the basis of brain size, limb-length ratios, and possible tool usage) to the better-characterized A. africanus and H. erectus classes. However, such a careful assessment is best done by those who have direct access to the fossils.

As noted above, once H. erectus appears, the rest of human prehistory appears to be a continuum, if one accepts evolutionary presuppositions. There is some gradual change in erectus cranial features from early to late periods, but then a blend of modern and erectus features appear in early H. sapiens and Neandertals just prior to and contemporaneous with fully modern forms.[51]

Some specimens exhibit such a mosaic of features that a precise label assignment cannot be made. This makes it difficult to deduce when, where, and how modern man appeared.

Lubenow, a young-earth creationist who feels the earth is only a few thousand years old, reviews the above fossil data and concludes that the diversity in the entire Homo taxon reflects only racial differences, not an evolutionary or species development.[52] Other researchers (both secular and Christian) consider the dating information to be generally reliable, and have proposed other models that take into account the time intervals and diversity observed. The key differences between these models depend on their assumptions about the level and type of interaction among the global H. erectus population.

Following the early intercontinental distribution of H. erectus around 1.5 mya, the multi- regional model proposes that this species globally evolved into modern H. sapiens because a sufficient level of interbreeding throughout the dispersed population was maintained over this long time period. Proponents for this view argue that the similarity of ancient and modern skulls found in a given location (particularly China, Australia and the Far East) implies that the hominid population in that geographic area has been stable for hundreds of thousands of years.[53]

However, many doubt that H. erectus populations intermingled over thousands of miles at a sufficient level to keep the advance to H. sapiens globally synchronized. On the other hand, the replacement model proposes that all modern populations result from a recent global migration of mankind from a single locale that replaced any earlier hominids (such as Neandertals) whenever they came in contact.[54]

Total replacement proponents are quick to point out that “Rambo-like invasion” characterizations of their model are inaccurate; a simple subsistence advantage that reduces mortality by two percent in the new population will enable it to replace the older group without violence in less than one thousand years.[55] Moreover, in some geographical areas there may have been nothing to replace: Earlier hominid populations may have died out or been reduced to minimal levels by climate change or disease before the immigrants arrived. Of course, some hybrid of these two models is possible, that combines one or more late, major waves of migration with some intermixing with older native populations.

These two models view the origin of advanced culture and language quite differently: In the multi-regional model, culture and language foster isolated pockets of hominids that intermix gradually over time. The replacement model typically sees culture and language as the competitive edges aiding the global expansion of one advanced hominid from out of Africa (at least this is where the oldest known fossils are found) sometime within the past 100,000 years.

We should note in passing that either of these secular models is compatible with a special creation of mankind, either by placing a Homo erectus Adam at the root of the multi-regional model, or by placing an anatomically modern human Adam as the source of the replacing population. There are advantages and drawbacks to either approach, but space does not permit a full analysis of both models. Consequently, we will limit our discussion to the hypothesis the author favors, that of a recent modern Adam.

IV. Biochemistry: The New Database.

Besides offering new tools for fossil analysis, other scientific disciplines are finding new data sources that contribute to the origins question. The most significant of these involves the realization that DNA, the chemical in the nucleus of every cell which stores the information necessary to manufacture the proteins, cells, organs, and structure of the entire human body, also contains clues about the biological history of man. Biochemists are now able to compare the DNA and protein sequences of modern animals, and on the basis of the small differences found, they can estimate the chemical similarity of man and the lower primates. The similarity appears to be very high: DNA reportedly differs by about 2%, and proteins by about 0.3% between human and chimpanzee, the closest lower primate, although the disparity has increased as our comparison techniques have improved.[56] Based on this small difference and on estimated rates of sequence variation over time, it has been deduced that a hypothetical last common ancestor to man and African apes existed as recently as five to seven million years ago.[57]

Another valuable biochemical insight involves the analysis of mitochondrial DNA from a world-wide sample of people. This form of non-nuclear DNA, which is only inherited from the mother, appears to show that all living humans are more closely related to one another than the multi-regional model of human evolution suggested. In fact, the mitochondrial DNA similarity is so high that the initial researchers inferred that the female ancestor common to all modern humans lived as recently as 90,000 to180,000 years ago.[58] However, this recent-date assignment and its interpretation as a single individual has come under strong attack and may need revision in light of statistical limitations inherent in the analysis.[59]

Nevertheless the data clearly show that all humans are very closely related to each other. Studies of chimpanzees and apes show that much more genetic diversity exists within each of these primate species than exists within the human family. To many this implies that a “pinch” or “bottleneck” occurred in the human population in the recent past.[60]

Technological improvements in the study of nuclear DNA now permit researchers to progress beyond bulk comparisons of similarity (such as the 2% figure noted above) and undertake a detailed comparative study of specific sequences. In some DNA regions, especially those that carry the information for allowing the human immune system to distinguish friend from foe (called the major histocompatability [MHC] genes), considerable patterns of variation are observed between individuals. These patterns are used to form the equivalent of molecular fingerprints on the cell surface, and their variability is so high that it is very unlikely that any two people will have identical cellular fingerprints. While this variability made organ transplants very difficult before the advent of immunosuppressant drugs, the benefit of this personalized cellular ID system is that it is extremely difficult for bacteria and parasites to invade the body.

Research has been undertaken to compare the MHC-gene patterns in humans with those of other primates. These transspecies polymorphism studies found that some patterns are more similar between species than within species. The researchers deduce from this that the number of similar patterns between species must be proportional to the number of common ancestors that both species shared. For the sake of illustration, let us say that there are ten patterns whose sequence is much more similar between humans and chimpanzees than it is between any other human-human or chimp-chimp combination. We also know from our genetic studies that each individual can carry only one of these patterns. The fact that these ten human-chimp patterns exist in common today implies that at least ten different individuals, each carrying one of the unique patterns, comprised the group that formed the last common ancestors to both the human and chimpanzee. In other words, the number of sequence patterns which two species have in common is proportional to the genetic diversity (i.e., group size) of the last common ancestors to both species.[61]

Using this reasoning with the currently known number of similar patterns between humans and chimps allows the secular researchers to assert boldly that “MHC polymorphism categorically rules out the possibility that modern human populations are derived from a single individual — an Eve.”[62]

As with any conclusion, the assumptions and data which lead to it need to be carefully examined. For example, the forces that give rise to the diversity seen in the MHC genes are poorly understood. Similar patterns between humans and chimpanzees may result because both need this specific pattern to ward off a common parasite. Consequently the MHC genes show a common “history” because both populations (or population subgroups) have successfully – but independently – fought off the same enemy. A common history of exposure to pathogens is a far cry from common ancestry. It remains to be shown that the common chimpanzee-human patterns arose without any external selection pressure. Otherwise, the data do not distinguish a common pathogen or other convergent pressure from a common ancestor.

Furthermore, continued transspecies polymorphism studies using larger population samples may find too many similar human-chimp patterns. Using the above logic, this would make the required number of founding individuals impossibly large and create a conflict with a fundamental assumption in evolutionary population genetics: evolutionary change requires small populations. If the group is too large, genetic novelties will not statistically dominate. As the human genome is better understood, the total number of common patterns found between species may require an unreasonably large founding population, implying that this transspecies similarity has other than ancestral origin.

This, in fact, is the conclusion that current MHC researchers have drawn: “…most of MHC diversity is de novo generated and not as the result of their trans-species inheritance as initially thought (Figueroa et al. 1988; Lawlor et al. 1988). This result finally puts the MHC in line with the bulk of population and evolutionary genetics data which firmly conclude that a narrow bottleneck has occurred at the origin of our species (Cann et al. 1987; Hammer 1995), a fact inconsistent with massive flow of alleles from one species to the next as required by the transspecies postulate (Ayala et al. 1994).”

Lastly, as the attacks on early mitochondrial-DNA conclusions have shown, the computer programs used to deduce genetic similarity between variant sequences are not as unbiased as previously thought. They are affected by the order in which the data are entered and often do not converge to a single obvious solution.[63] However, as these tools are refined, they are revealing some startling results: Ann Gauger re- analyzed the human-chimp MHC-DRB1 gene that factored heavily in Ayala’s work, and found that it is quite possible for modern humans to have come from just two parents.[64]

Just as the mitochondrial DNA in a woman’s egg is passed on to all of her descendants and does not mix with any genetic material from the man, the male Y chromosome is passed on to all male descendants and does not mix with any genetic information from the woman. Consequently there is intense interest in studying the Y chromosome[65] to see if it shows the same very low variation that the mitochondrial DNA does. The first results from one section of a gene on the Y chromosome found no variation in it. Based on the rate that this same section appears to vary in other primates, the researchers estimated that the male ancestor common to all modern humans existed around 270,000 years ago. An extremely low diversity in other sections of the male Y chromosome has also been reported by other researchers.[66] These results agree well with the mitochondrial dates and provide independent confirmations of the recent pinch, bottleneck or replacement model.[67][68]

After twenty years of research, Svante Pääbo and others isolated mtDNA from poorly-fossilized Neandertal remains and reported that there are sufficient differences between the recovered Neandertal and modern human sequences to conclude that no Neandertal mtDNA genetic information occurs in modern populations.[69] This result lends strong support to a replacement model, for if extensive intermixing of the established Neandertal and incoming modern human population had taken place, some genetic evidence of this should persist in modern mtDNA.

Further work by Pääbo and others on Neandertal nuclear DNA has lead him topropose (unexpectedly) that there is between1-4% of Neandertal nuclear DNA in the modern human non-African population.[70]

This implies a rare and early interbreeding of Neandertal males with modern females, since there is not mtDNA evidence to suggest that Neandertal females contributed to the modern human lineage. However, this interbreeding proposal has been challenged by other researchers, who point out that this interpretation makes assumptions about ancient human population diversity that are likely incorrect.[71]

For all of the emphasis we hear about the similarities between humans and Neandertals and chimpanzees, it is worth noting the striking and unexpected differences between these species which are suggestive of a distinct creation for Adam and Eve, yet are glossed over by the popular media. In 2010 a detailed comparison map of the human and chimp Y-chromosome was announced, revealing far more differences (>30%) than would be expected if there were a recent human-chimp common ancestor. Although attributing this disparity to very rapid evolution, the researchers nevertheless commented, “Indeed, at six million years of separation, the difference in MSY gene content in chimpanzee and human is more comparable to the difference in autosomal gene content in chicken and human, at 310 million years of separation.”[72]

Another striking difference involves two classes of viruses which infect a wide range of primates. Simian foamy viruses (SFVs) and simian infectious retroviruses (SIVs) are common, mild infections that occur in species-specific varieties. However, they are not found in humans, although people can catch them if they work in close quarters with primates. One researcher comments, “Assuming that the common ancestors of hominids carried multiple endemic infectious retroviruses, how did the human lineage eliminate them? Given that humans remain susceptible to re-infection with both SFVs and SIVs from other hominids, this seems unlikely to be explained solely on the basis of more efficient host restriction systems. Rather, there seems to have been an episode in which the ancestral human lineage was somehow ‘purged’ of these endemic viruses.”[73]

This situation would seem to count as evidence against the common ancestry hypothesis.

DISCUSSION.

Up to this point we have only reviewed data from the natural sciences that may bear on the origin of man. Many Christians, of course, recognize that special revelation is another source of knowledge that bears on this issue. We will now turn our attention briefly to the biblical material and highlight the tension that sometimes occurs when scientific data and revelation both speak to the same question.

Within the conservative Christian community there is a wide range of opinion on how to interpret the biblical material which relates to Creation. Some treat the Creation narrative as if it stopped after Genesis 1:1 and distance themselves from the host of other details provided in the next two chapters. This group views the order of creation, special creation of Adam, Garden of Eden, and Fall as God’s allegorical attempts to explain to the ancient, primitive Hebrews their place in the universe and the origin of sin.[74]

Others propose a literal interpretation, taking a simple reading of the English text as historical and scientifically accurate.[75]

To the author it appears that the truth lies somewhere between these positions. One treads dangerous territory if one ignores the linguistic and cultural difficulties of attempting to decipher an ancient text, or if one dismisses any attempt to understand the passage as historical by inferring that God was so bound by his early audience that he could convey nothing in Genesis of future relevance to modern man. It seems wisest to propose that this simple yet sophisticated narrative contains a highly abbreviated summary of the origin of the Earth and mankind.[76]

Like other passages, early Genesis does not address a host of items of interest to contemporary specialists in a particular field: The Bible focuses on salvation history and only fills in cultural and background details as they are relevant to the immediate context, not for the curiosity of readers thousands of years later.[77] Nevertheless, the events that are described should be understood as real and historical, especially in light of their implications for mankind. For example, the institution of monogamous marriage, the origin of sin and the resultant corruption and mortality of mankind, are all grounded in God’s interaction with a single male-female pair of human beings, from whom all mankind are descended. If anthropology forces us to replace Adam and Eve with a global homo erectus population that collectively evolved into modern man, then the theological foundation for the nuclear family, sin and death appears to be eroded.[78] The credibility of the Bible when it speaks on these issues seems to be damaged: If it does not correctly explain the origin of a problem, why should one trust its solutions?[79]

As an example of this integrative tension, let us focus on one specific question, Was Adam created directly from non-living matter or did he have hominid parents? Genesis 2:7 reads, “Then the LORD God formed man of dust from the ground, and breathed into his nostrils the breath of life; and man became a living being.” [NASB] In contrast to previous creative acts where God said, “Let the earth bring forth….”, the picture here is that God is actively involved in giving life to a substance that was not previously living.[80]

It is striking that most of the specific features in this verse clash with the anthropological and biochemical models which we have reviewed. Modern scientific theories propose that man and apes share a common ancestor in the past, that the transition to modern man took place gradually over thousands of years, and that small groups or clans of hominids (not one or two individuals) were involved in the process. Some claim that a sudden jump from non-life to modern man, or even from an individual primitive ancestor to a modern man, is absolutely ruled out by the diversity seen in the biochemical[62] and fossil data.[53]

Some Christian scholars dismiss or excuse these apparently erroneous statements by asserting that the Bible here is limited by its primitive cultural setting: The ancient writers and readers of Genesis were restricted by ancient near eastern cosmology in the way they viewed themselves and the world. This mind set so permeates biblical passages like this that no modern scientific conclusions can be or should be drawn from it. However, conservative scholars hasten to add that these limitations do not hamper our ability to deduce theological truths from the text.[74]

This argument overlooks the fact that ancient cosmologies exhibit considerable variety. In fact, some creation stories from neighboring cultures agree better with the modern scientific one because they lack the “embarrassing” features that a single man was created and that he was formed from purely non-living matter. The Atra-hasis epic describes the gods making men from the flesh and blood of a god mixed with clay;81 thus man in this scheme is partially made from already-living material. Moreover, the text notes that seven male/female couples were created at the same time, rather than a single man.[82]

Neither can we assume that apes or similar primates were unknown to the primitive Hebrews. An alabaster statue of an ape found in Susa [Persia] dates back to the Proto-Urban period (c. 3300 BC).[83] Apes (or possibly monkeys) are mentioned as curiosities in Solomon’s court (1 Kings 10:22) but were common in Egypt.

Perhaps the notion of common ancestry between man and other animals was too difficult or repulsive for the primitive mind? It is hard to imagine how this would be more negative than being called “dirt” by God in Gen. 3:19. If the writer of Genesis had wanted to avoid unpopular concepts, he would not have stressed that all mankind have a common ancestor! A multi-Adam model would find easier acceptance because it can justify the intercultural and interracial hatred that characterizes so much of human history.

In light of the comparative literature and cultural knowledge available to us, we cannot presume that it was impossible for the writer of Genesis to explain to his ancient audience that God empowered a small group of already-living beings that shared many common features with apes to develop gradually into mankind. God could have told the story of a hominid-origin for mankind in a manner the early Hebrews could have grasped. The fact that he did not must have some significance.

Returning to the natural sciences, we find that the available data used to support the theory of hominid evolution do not show a smooth, gradual transition from earliest australopithecines to university professor. Two recent, abrupt changes occur in the data: A cultural one at around 40,000 BC, when art appears and the complexity and variety of artifacts greatly increases; and an anatomical one at around 130,000 BC when anatomically modern human remains first appear.[84] [85] At present either of these transitions seems sharp enough that we can propose that the special creation of man occurred in one of these gaps and that it was not bridged by purely natural means.

One challenge that the scientific data pose for a recent special creation model is the clear evidence that a variety of fairly advanced hominids existed on the earth either immediately before, or contemporary with, modern man. The Bible does not mention any hominids in the animal population, so if we place Adam at a late gap in the hominid record (as we have done with either date above) then we must assume that Adam had non-human contemporaries who made stone tools and used fire. However, as already noted above, DNA and mtDNA studies strongly imply that these preadamic hominids were replaced by modern human populations and that no (or rare) interbreeding took place.[86] We could speculate that this preadamic hominid population formed a cultural “safety net” for Adam and Eve, so that after they were expelled from the Garden they could survive in the wild by adapting the skills of the hominids around them. These hominids might be the reason for Cain’s fear that “whoever finds me will kill me” when he is cursed by God after killing Abel (Genesis 4:14).

The above consideration of the special creation of man is often ridiculed as an ad hoc “God of the gaps” special pleading by secular naturalists and some Christians.[87] However, all parties agree that several gaps and apparently rapid transitions exist in our present-day knowledge of human prehistory. The problem is how to deal with them. The special creationist presumes that at least one gap is real – corresponding to God’s direct intervention in a world that he normally controls providentially, through what we call natural processes. The naturalist (either theist or atheist) presumes that all gaps are only apparent ones because the appropriate fossils have not been found or did not survive. Consequently he bridges all gaps with natural processes and sees no need for God to tinker with his creation (or he sees no need for God at all). This approach requires a strong faith in “naturalism of the gaps,” but the naturalist argues that this is justified by the theory of common ancestry.

The theory of common ancestry is the cornerstone of modern evolutionary theory. In its simplest form, it merely states that everything that lived had parents. Once the first living cell formed, all other life on earth descended from it. Evidence typically given as proof for this theory is the uniformity of the genetic code and the high degree of similarity in DNA, biochemical composition, structure and function of proteins, cells, organs, and higher animals. This similarity can be explained simply and elegantly by the purely naturalistic mechanism of common ancestry. Everything looks similar because they share common parents sometime in the past.

Many scientists view the theory of common ancestry as so obviously true (“the fact of evolution”) that details about the exact mechanism of macroevolution (gradual change, punctuated equilibrium, or some yet unknown process) do not disturb them.[88] Such a deep faith in this solely naturalistic model blinds many to any other possible explanations for this similarity, such as the theory of a common designer or engineer.

In the matter of human origins, creationist theories (whether young- or old-earth) propose that at least one of the observed gaps in the fossil and/or cultural record is real and is not an artifact of our limited knowledge of the past. At some point in natural history God made man by a direct means. Of course, we can still ask why God made man so similar to modern apes – or more importantly – to the other hominids that were contemporary with early man.

Perhaps if we reword this question we can see better how to answer it. Let us instead ask, “Does man have to be different to be proof that God made him directly?” (For the sake of argument we will ignore the clear differences in language ability and culture that do distinguish man from animals and other hominids, since a skeptic would dismiss these as secondary traits). The answer to this is simple: No. We know that many of Jesus’ miracles produced results that looked like they had a history and were completely natural (e.g., the wine at the wedding in Cana, the bread used for feeding the 5,000), so some of God’s miraculous actions can be difficult to distinguish from his providential ones unless we were there at the time the miracle took place or have additional knowledge about the circumstances surrounding it. The author views the special creation of man to be such a case. The Bible tells us something about the history of man that we may not be able to deduce from the surviving evidence: Man was a special creation. Why did God choose not to modify an existing hominid, but make something very similar from scratch? Perhaps to indicate man’s relative importance before God or to signify that man is the capstone of his creation. Certainly from reading Genesis we do not get the sense that there is anything “bad” in what is created up to this point that God would have an aversion to using as a template for his final work.

A rough analogy might be a business letter, dictated to and typed up by a secretary, but signed personally by the president of the firm. All of the content of the letter comes from the president, but the signature involves his own personal action and serves as a stamp of approval, authenticating the contents. Man is God’s personal “signature” – his own handiwork – embedded in the rest of creation.

Another analogy, this time from the ancient near east, involves the building or refurbishing of a temple. A key element in this massive undertaking involved the making of the first brick for the new construction. In an elaborate ceremony, the king personally mixed the water and mud and molded it.[89] Once this first brick was made, then the manufacture of the rest of the bricks by ordinary workmen could begin. It was not considered demeaning for the king to stoop to make a brick himself, but was a great honor. The king’s brick did not have a composition any different than the others; yet because it was made first by the king personally, it was clearly the most important one. In a similar way, God’s creation of man is significant not because of man’s unique physical composition, but due to God’s direct involvement in the process.

While the theory of a common designer is assumed when studying artwork in order to determine the style that is characteristic of a given painter, with self-replicating systems it may be hard to distinguish self-modification from external adjustment. In cases where a substantial increase in complexity occurs, external adjustments can only be ruled out if the mechanism of self-modification is well understood and if sufficient intermediate forms existed to demonstrate that no discontinuities occurred. Otherwise it is unwise to presume that a natural mechanism is the only possible means to bridge the gap.

If the goal of science is to determine what actually happened rather than to construct the most plausible naturalistic rationalization of what could have happened, then we must apply our presumptions cautiously. As Einstein noted in another context(quoted in our foreword), the presuppositions in a theory can mask data so that people no longer see other possibilities. If “science” is defined so that the actions of a supernatural agent are considered out-of-bounds or even irrational, we should not be surprised if science cannot see God’s handiwork through its self-imposed blindness.

Is there an objective means to resolve the clash between naturalistic and interventionist presuppositions?[90] More data will certainly fill in the existing gaps in our knowledge and help us determine which apparent transition is real or not. Research on several fronts will doubtless be helpful: More intermediate hominid fossils will help trace where gradual change in skeletal features did or did not occur; continued comparative studies between human and primate DNA will give us a more detailed picture of our similarities and differences, providing more clues as to its significance; archaeological discoveries in biblical studies may find new material that will help us better understand early Genesis.

For the present the author feels no compulsion to bridge all of the gaps in hominid evolution with naturalism instead of theism. The clear break from hominid to human culture, the high similarity of modern human DNA that implies even to secular minds a recent severe “pinch” in population, and the overall fragmentary nature of our present knowledge, should make us hesitant to ascribe the works of a common designer to common parents. What is encouraging is that as research in this area has progressed, the extra-biblical evidence for a historical Adam and Eve has actually increased. A century ago the dominant human origins model was multi-regional, calling for a “many Adam” solution. Even fifty years ago there was no scientific evidence for Adam’s historicity. Today however, genetic diversity data suggests a founding population size as small as 500-2000, spreading globally from one small region. Mitochondrial Eve, Y-chromosome Adam, and even the DRB1 gene converge to a single pair, that somehow was spared infection by the many viruses common to other primates. While not conclusive by any means – and it is impossible to be conclusive given that we are looking back at events in deep history – today there are actually several lines of scientific evidence for an historical Adam and Eve. Those who tell us that we must abandon this primitive myth and adopt a Darwinistic model for human origins may not be aware of these trends, because their implications are glossed over by naturalistic-thinking colleagues.[91]

In conclusion, it is worth noting that both science and theology benefit from the tensions that arise when the interpretations of the data from each field conflict. Neither field can claim to be an absolute guide to truth apart from the other: Theology learned from its geocentric/heliocentric debates with the natural sciences to be cautious in its interpretations, because some biblical language is phenomenological, just as many idioms of regular speech are.[92]

Likewise science learned to be cautious in its metaphysical presuppositions when it became clear that the universe is not eternal but appears to be created, something Christian theologians have argued for hundreds of years.[93]

In the case of human origins, no obvious resolution of the tension between the models seems possible at present, but neither is any model ruled out. By watching for blind spots in our presuppositions, double-checking the validity of our data and seeking more of it, perhaps we can arrive at a consensus that is more charitable to all.

On Human Origins: A Survey.

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