The African Adam and Eve theory, more technically known as the Mitochondrial Eve theory, posits that all contemporary humans can be traced to relatively recent African origins, possibly even with a common mother. This mother became known as Mitochondrial Eve or African Eve. The Mitochondrial Eve model postulated all contemporary humans derived from a lineage of anatomically modern humans, evolved in Africa around 150,000 years ago and then spreading all over the world.
Map depicting the migration of Homo sapiens out of Africa.
This idea debuted in January 1988, when Newsweek’s cover depicted “The Search for Adam and Eve”, reporting on a paper entitled Mitochondrial DNA and human evolution. This research purported that all contemporary humans could be traced to relatively recent African origins, maybe even with a common mother.
The Replacement Hypothesis
They named this the replacement hypothesis or out-of-Africa II because these anatomically modern humans seemed to have fully replaced the earlier populations who had migrated from Africa about 1.8 million years ago, such as the Neandertals and Homo erectus populations in Asia. The replacement hypothesis became dominant in textbook models of human evolution, while Mitochondrial Eve nearly became a pop icon. “The out-of-Africa replacement hypothesis became the model of human evolution, particularly in undergraduate textbooks and the popular science literature”.
Initial Resistance and the Multiregional Model
Initially anthropologists resisted a model derived purely from genetic evidence. Anthropologists studied fossils, and favored a model that emphasized gene flow and interconnection across the hominid species range. Known as the “multiregional model,” it was first proposed in 1946 by Franz Weidenreich, and then later developed and defended by Milford Wolpoff. However, after initial resistance, scientific consensus and most anthropologists shifted toward the replacement hypothesis and Mitochondrial Eve.
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The two main hypotheses of modern human origins: A) Out-of-Africa model and B) Multiregional model.
Most students either never learned about the multiregional model, or if they did it was an impoverished and inaccurate version of it. Following the original research, more studies seemed to disprove any genetic connection between contemporary humans and Neandertal or other archaic groups. The genetic evidence seemed more dazzling, more precise, and more computational than messing with fossils.
The Candelabra Hypothesis
Since the 1960s anthropology has been haunted by the candelabra model proposed by anthropologist Carleton Coon. As Robert N. Proctor observed, in an insightful and quite funny 2003 overview, “it seems pretty clear that the Out-of-Africanists are winning the field. The candelabra hypothesis asserts Homo erectus dispersed from Africa about 1.8 million years ago, and then Homo sapiens evolved separately in Asia, Africa, and Europe. This model is scientifically wrong but persists in popular imagination and supports racist thinking.
As noted in the section on Race Revival-Attacking Anthropology, the work of geneticist Richard Lewontin was very helpful for arguing against the genetic separation of human groups. Lewontin and especially Stephen Jay Gould explicitly embraced the replacement hypothesis. Many anthropologists had already promoted Gould’s open-ended view of evolution.
Some of the best anthropology documents human and natural richness in Africa. But for the rest of the world, Africa gets ignored, misrepresented, left off the map. Afflicted by poverty, inequality, military conflicts, and HIV-AIDS, sub-Saharan Africa has been sadly omitted from a globalizing world, seen as a hopeless basket case. By stressing the out-of-Africa replacement hypothesis, anthropologists could re-assert African primacy, contributing to ideas that “we are all African” or that everyone is indigenous to Africa.
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Turning of the Tide
In 2010 the tide turned. An innocuously-titled study A Draft Sequence of the Neandertal Genome documented Neandertal contributions to contemporary humans. Then, perhaps even more dramatically, researchers found that the archaic human remains found in Denisova Cave in Siberia also found some genetic match in contemporary humans. Homo sapiens interbred with both Neandertals and Denisovans, and the results show up in contemporary genome sequences.
“‘It’s hard to explain how good I feel about this,’ says Wolpoff, who says that seeing complete replacement falsified twice in 1 year was beyond his wildest expectations. ‘It was a good year’”. Of course, these studies do not prove a lot of interbreeding-it took some very sophisticated techniques to demonstrate any interbreeding at all-but the idea of no contribution from Neandertals, or that archaic populations are entirely separate species from modern humans, is no longer defensible.
In introductory classes to biological anthropology, both instructors and the authors of numerous textbooks have been tempted to present the origin of modern humans as two equally plausible, mutually exclusive evolutionary scenarios: the Out of Africa hypothesis and the Multiregional Evolution hypothesis. The bad news is that a more current representation of the consensus that most researchers have reached is likely to be more complex and convoluted. In addition, it can likely only be represented by models of human evolution destined to befuddle introductory students everywhere, complete with multiple slides, wandering migration arrows, question marks, and unapologetic blank spaces.
The 2010-2012 studies could have been a boon to anthropology if we had defended the multiregional model, but they now put some standard anthropological accounts in an awkward position. Talking about any kind of Eve, even a Mitochondrial Eve, does not help. Moreover, the acrimonious debate let a lot of people tune out, contributing to an idea that scientists simply have no idea what was going on.
The replacement hypothesis and Mitochondrial Eve offer a simple model of human evolution. It is easy to explain, and it eliminates the candelabra justification for race-thinking. Multiregional evolution is more complex and difficult to diagram. There is more room for misinterpretation. Weidenreich (1946) argued that regional populations could display differences, and some local differences could persist through time in the same locality, but there is no assumption of independent, parallel evolution.
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Instead, humanity consists of a single evolutionary lineage with no subbranches because humanity’s geographically dispersed populations were and are interconnected by gene flow and lines of recent, not ancient, common descent due to this gene flow. Anthropology had fossil evidence and forms of analysis different from the dazzle of genetic computation. What genetic computation cannot deliver is the full range of the evolutionary process, where evolutionary change can occur with or without genetic modification.
Much genetic change occurs without any corollary on the level of form or behaviour; conversely, significant morphological or behavioural transformation may occur without any corresponding changes in the genome. The replacement hypothesis is perhaps less racially charged than the candelabra model, but the idea that anatomically modern humans set out from Africa and then replaced all other populations is one of colonization and domination. It is striking how accurately this [out-of-Africa] hypothesis mirrors the story of global colonial conquest by White Europeans so much favoured by Darwin and his contemporaries.
The story may have been turned upside down, but the structure is the same: one dominant race, equipped with superior intelligence, supersedes the rest. The different rhetorical strategies used by replacement versus multiregionalist theorists are interesting in this context, given that each side has tried, at various points, to accuse the opposing camp of being more racist. Out-of-Africanists have accused multiregionalists of exaggerating racial divisions (conceived as going back as far as a million years in some candelabra models); multiregionalists in turn have accused Out-of-Africa advocates of implying a total and perhaps violent (genocide-like?) replacement of H. erectus (or Neanderthals) by H. sapiens.
The original authors of the Mitochondrial Eve research in 1987 lumped Wolpoff and Weidenreich’s model together with the candelabra model from Coon. Textbooks perpetuated this error, portraying multiregional evolution as candelabra with some gene flow. Anthropologists may have hoped the out-of-Africa hypothesis with a Mitochondrial Eve in Africa would bring much-needed attention to sub-Saharan Africa, as a celebrated cradle of humanity. It did not. Instead, people began to imply that leaving Africa was a good thing.
Extreme versions of Mitochondrial Eve and the replacement hypothesis are gone. It is time to recapture the complexities of anthropological models. In June 2017, Carl Zimmer reports that Oldest Fossils of Homo Sapiens Found in Morocco, Altering History of Our Species. Indeed, this re-setting of the clock-with Anatomically Modern Humans debuting in Morocco around 300,000 years ago-should be yet another blow to the Mitochondrial Eve ideas. However, it should very much support that the first modern humans originate in Africa.
In January 2018, I asked for support Dr. For anyone looking on and wondering: Not only is “exodus” unscientific but it belongs in and supports the very real racial/racist narrative out there in the world where human origins is explained as if “modern humans” had to get the hell “Out of Africa.” We have to do better.
The quote from Robert N. Proctor’s Three Roots of Human Recency (2003) remains relevant: “I call this ‘Out-of-Africa: Thank God!’ to point to the presumption that hominids became human in the process of leaving Africa-a slight that seems always unintentional, yet is surprisingly common.
Reconciling Faith and Evolution
Mitochondrial Eve: Debunking the Myths of Our Single Female Ancestor (Out of Africa Explained)
Religious people everywhere struggled with Darwin's findings. Catholic priest Friedrich Stenger has lived in Africa for decades - most recently he taught at the Catholic Tangaza College in Kenya's capital, Nairobi. "Once a biology teacher in Ethiopia told me that [evolution] was in conflict with the church because on Sundays the pastor would say that the world was created 4,000 years ago," Stenger told DW. "The teacher said to me: As a scientist, I know this cannot be true. For a long time, the Catholic Church would not budge on the issue. It was not until the 1950s that it slowly began opening up to the theory of evolution. In 1986, Pope John Paul II commented that a belief in evolution and having faith in God need not be mutually exclusive.
"What the story of creation means to tell us is that God is at the beginning of creation," says Stenger. "Science is able to tell us this in more detail, which is why the theory of evolution is very important." However, not all Christian churches share this view.
Abdulkader Tayob, a professor of Islamic studies at the University of Cape Town, has also thought a lot about how faith and evolution can be reconciled. "The belief of many Muslims, like many Jews and Christians, is that God created everything out of an absolute will and that man is, so to speak, the pinnacle of creation," he told DW.
Individual Islamic scholars have already commented on these issues, but a genuine debate on ways to unite faith and evolution does not yet exist in the Islamic world, says Tayob. Pentecoastal churches from Kenya to Mozambique openly oppose the evolution theory. In religious schools, evolution is often not taught at all. In state-run schools, it is not always included in the syllabus. In South Africa, for example, the teaching of evolution was only introduced in 2008. The limited amount of resources and training available also means that youngsters often do not get the chance to engage with the subject.
But how can creation and evolution be reconciled in Islam? Tayob suggests approaching the creation story found in the Koran from a different perspective. "The history of the Koran when it comes to human origins, when it comes to the history of human society, is told in so many different ways in so many different parts of the Koran," he says.
Addressing Common Misconceptions
The popular name "mitochondrial Eve", of 1980s coinage, has contributed to a number of popular misconceptions. The definition of Mitochondrial Eve is fixed, but the woman in prehistory who fits this definition can change. That is, not only can our knowledge of when and where Mitochondrial Eve lived change due to new discoveries, but the actual Mitochondrial Eve can change.
The Mitochondrial Eve can change, when a mother-daughter line comes to an end. It follows from the definition of Mitochondrial Eve that she had at least two daughters who both have unbroken female lineages that have survived to the present day. In every generation mitochondrial lineages end - when a woman with unique mtDNA dies with no daughters.
When the mitochondrial lineages of daughters of Mitochondrial Eve die out, then the title of "Mitochondrial Eve" shifts forward from the remaining daughter through her matrilineal descendants, until the first descendant is reached who had two or more daughters who together have all living humans as their matrilineal descendants. Because mtDNA mapping of humans is very incomplete, the discovery of living mtDNA lines which predate our current concept of "Mitochondrial Eve" could result in the title moving to an earlier woman.
Sometimes Mitochondrial Eve is assumed to have lived at the same time as Y-chromosomal Adam (from whom all living males are descended patrilineally), and perhaps even met and mated with him. Even if this were true, which is currently regarded as highly unlikely, this would only be a coincidence. Like Mitochondrial "Eve", Y-chromosomal "Adam" probably lived in Africa.
Mitochondrial Eve is the most recent common matrilineal ancestor, not the most recent common ancestor. Since the mtDNA is inherited maternally and recombination is either rare or absent, it is relatively easy to track the ancestry of the lineages back to a MRCA; however, this MRCA is valid only when discussing mitochondrial DNA.
The time period that human MRCA lived is unknown. Rohde et al put forth a "rough guess" that the MRCA could have existed 5000 years ago; however, the authors state that this estimate is "extremely tentative, and the model contains several obvious sources of error, as it was motivated more by considerations of theoretical insight and tractability than by realism."
Just a few thousand years before the most recent single ancestor shared by all living humans was the time at which all humans who were then alive either left no descendants alive today or were common ancestors of all humans alive today. However, such a late date is difficult to reconcile with the geographical spread of our species and the consequent isolation of different groups from each other.
For example, it is generally accepted that the indigenous population of Tasmania was isolated from all other humans between the rise in sea level after the last ice age some 8000 years ago and the arrival of Europeans. In other words, "each present-day human has exactly the same set of genealogical ancestors" alive at the "identical ancestors point" in time.
Genetic Data and Dating Uncertainties
Dating of the genetic events, such as the time hominids migrated out of Africa, is very uncertain. Mutation is not a constant event, and assuming a constant rate for mutation to be used in this calculation of dating genetic events could lead to serious errors. Since both the African Eve and Multiregional theories are based on African origin, any genetic data without proper dating would support either theory.
A serious effect of ignoring hominid evolutionary processes beyond 100,000 years ago is the loss of input data to research. For example, the effect of bipedalism would not be included in the study of evolutionary psychology and other evolution-related science, since bipedal development is believed to have occurred much earlier than 100,000 years ago.
Evidence for Replacement
Although we humans often judge ideas on their plausibility, plausibility is not a rigorous test of the validity of scientific ideas. Whether we can envision it readily or not, the replacement of one species by another invasive species has happened repeatedly on large landmasses with abundant food supplies.
What evidence might we find of such a replacement? Three possibilities come to mind. First, as Dr. Chou suggests, the style of tools in a geographic area might change if tool-making invaders arrived. The archaeological record does not give us clear evidence either of replacement or of its lack. Second, a change in anatomy or morphology of the fossils should reveal whether an indigenous species has evolved or whether another species has moved in from elsewhere. Unfortunately, Out of Africanists and Multiregionalists cannot agree on whether there is good evidence of morphological continuity in the fossil record of the genus Homo within any single geographic region.
Third, we can turn to genetics. Evolution in situ will leave evidence of genetic continuity; replacement by another lineage will not show such continuity. This is where the comparison of mitochondrial DNA (mtDNA) extracted from various hominids has provided strong evidence of replacement. For confirmation, similar studies should be conducted on Asian and African fossil and modern humans.
Dr. Chou is right when he observes that dates based on molecular clocks are uncertain. Fortunately, dates based on fossils are very accurate, when the specimens have been buried in sediments with the appropriate geochemical attributes. The occurrence of fossils with modern anatomy thus provides a good check on the molecular dates. This is why the most compelling answers come from the consilience of genetic and fossil evidence.
Dr. Chou fears that evolutionary developments in our lineage that are older than the origin of modern humans will be ignored, to our peril. I agree wholeheartedly. The human species as a biological entity is deeply rooted in primate, mammalian and vertebrate evolution.
Mitochondrial Eve: A Single Woman?
It has been proposed that modern humans descended from a single woman, the "mitochondrial Eve" who lived in Africa 100,000 to 200,000 years ago. The human immune system DRB1 genes are extremely polymorphic, with gene lineages that coalesce into an ancestor who lived around 60 million years ago, a time before the divergence of the apes from the Old World monkeys. The theory of gene coalescence suggests that, throughout the last 60 million years, human ancestral populations had an effective size of 100,000 individuals or greater. Molecular evolution data favor the African origin of modern humans, but the weight of the evidence is against a population bottleneck before their emergence.
In human genetics, the Mitochondrial Eve is the matrilineal most recent common ancestor (MRCA) of all living humans. The male analog to the "Mitochondrial Eve" is the "Y-chromosomal Adam" (or Y-MRCA), the individual from whom all living humans are patrilineally descended. As the identity of both matrilineal and patrilineal MRCAs is dependent on genealogical history (pedigree collapse), they need not have lived at the same time.
| Concept | Description |
|---|---|
| Mitochondrial Eve | Matrilineal most recent common ancestor of all living humans, traced through mitochondrial DNA. |
| Y-chromosomal Adam | Patrilineal most recent common ancestor of all living humans, traced through Y-chromosome DNA. |
| Out of Africa Theory | The hypothesis that modern humans evolved in Africa and then migrated to other parts of the world, replacing other hominid populations. |
| Multiregional Evolution | The hypothesis that modern humans evolved simultaneously in different regions of the world from earlier Homo erectus populations, with gene flow between these regions. |
| MRCA | Most Recent Common Ancestor |
Early research using molecular clock methods was done during the late 1970s to early 1980s. Allan Wilson, Mark Stoneking, Rebecca L. Cann and Wesley Brown found that mutation in human mtDNA was unexpectedly fast, at 0.02 substitution per base (1%) in a million years, which is 5-10 times faster than in nuclear DNA.
By 1985, data from the mtDNA of 145 women of different populations, and of two cell lines, HeLa and GM 3043, derived from an African American and a ǃKung respectively, were available. After more than 40 revisions of the draft, the manuscript was submitted to Nature in late 1985 or early 1986 and published on 1 January 1987.
