Humans Considered to have Evolved Separately for 100,000 Years

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New research published in the American Journal of Human Genetics purports to describe how humankind diverged, then nearly went extinct, and then finally reunited more than 50,000 years ago—at least, that’s the hypothesis. Associated Press and BBC News articles also take a look at different aspects of the epic chapter of human history supposedly uncovered by the study.

Researchers at the Genographic Project, a team assembled three years ago to conduct genetic anthropology, analyzing mtDNA suggest that two people groups in southern Africa seem to have diverged from the rest of humanity between 90,000 and 150,000 years ago. Other studies have suggested that drought/severe climate conditions nearly killed off the human population some 70,000 years ago (and was considered the potential cause for this separation), but that humans ultimately came back together.

Referencing work done separately at Stanford University, the researchers estimated that the human population may have fallen to only 2,000 before numbers bounced back after the bottleneck.

Spencer Wells, director of the Genographic Project, praised the study’s significance:

This study illustrates the extraordinary power of genetics to reveal insights into some of the key events in our species’ history. Tiny bands of early humans, forced apart by harsh environmental conditions, coming back from the brink to reunite and populate the world. Truly an epic drama, written in our DNA.

...humans ultimately came back together.

An ancient drama of separation, near-destruction, and ultimate triumph—how did the researchers come to these epic conclusions, and how did they determine the date, place, and cause of this drama? Is this purported detailed human history of tens of thousands of years ago really written in our DNA?

The way the news sources present this chapter of human history, you might think it were written on stone tablets—an unquestionable fact in the history of man. In fact, the story is a piecemeal elaboration from several separate research projects of what may have been—if you accept a number of assumptions.

First, what did these scientists actually do and what did they really find? The studies focused on mitochondrial DNA of the Khoi and San (Khoisan) people in southern Africa.1 Evolutionary scientists believe that by analyzing differences in the mtDNA of two individuals (or two people groups), they can construct a “family tree” of sorts to determine exactly how long ago two individuals (or two people groups) diverged. However, there are critical assumptions involved in using this “molecular clock,” as it’s called, to establish dates for human history (as we’ll look at below).

The legacies of this divide are different mitochondrial lineages.

The family tree the team constructed showed an ancient divide in early humans (a divide they date to 90,000–150,000 years ago). The legacies of this divide are different mitochondrial lineages: one set found in the Khoisan people, other sets found in Africa, and eventually worldwide. The BBC News notes that Africans today harbor a mixture of these lineages.

The researchers then took these facts and built one interpretation of the facts—their “epic story”—based on evolutionary assumptions. Most critical is the assumption that comparing differences in mtDNA can lead to near-perfect family trees, along with the assumption of around 5000 years for each mtDNA mutation, which allows evolutionists to put such old dates on these happenings. These in turn are based directly on evolutionary ideas about when humans and chimpanzees shared a common ancestor (and thus looking at differences between humans and chimpanzees and then interpolating mtDNA changes in the time since then).

The researchers also built their story on the assumptions that humankind originated in Africa and that climate change in the past 150,000 years affected early humankind. And, of course, these assumptions are based on other evolutionary interpretations of various legitimate studies, with those interpretations also based on assumptions as well!

It’s no surprise, then, that BBC News notes, “other scientists said it was still too early to reconstruct a meaningful picture of humankind's early history in Africa [and] argue that other scenarios could also account for the data.”

For instance, University of Pennsylvania population genetics expert Sarah Tishkoff hypothesized that the Khoisan may have once carried more of the “East African” lineages, but that those could have been lost over time. “Although there is very deep divergence in the mitochondrial lineages, that can be different from inferring when the populations diverged from one another and there can be many demographic scenarios to account for it,” she told BBC News.

At the root of these different views is the issue of where we go when we want to learn about human history—God’s Word or human assumptions about our past, including the origin of the DNA in our cells? Both require certain presuppositions; one requires us to start with the presupposition that God’s Word is a totally accurate account of human history; in the same way, the other requires us to start with the presupposition that the present is the key to the past, that only natural (as opposed to supernatural) events can account for divergences in, e.g., human mitochondrial DNA, and that humans evolved from other primates. Let’s stick with the Bible as our presupposition and explain this mtDNA divergence.

We know that all humans who exist today descended from three couples who joined Noah and his wife on the Ark.

Starting with the Bible and acknowledging Noah’s Flood as a real historical event, we know that all humans who exist today descended from three couples who joined Noah and his wife on the Ark: the sons of Noah and their wives—Mr. and Mrs. Ham, Mr. and Mrs. Shem, and Mr. and Mrs. Japheth. Since mtDNA is passed along by mothers only, not fathers, Shem, Ham, and Japheth would have all had Noah’s wife’s mtDNA, but could not have passed it on.

Noah’s three daughters-in-law, then, are responsible for the original post-Flood mtDNA diversity. So let’s say the differences between the mtDNA of Mrs. Ham, Mrs. Shem, and Mrs. Japheth were already substantial, based on mutations from before the Flood. Scientists who ignore the bottleneck of the Flood fail to take into account this source of mtDNA diversity.

From the time the party stepped off the Ark to the time the party was over at Babel, the grandsons and granddaughters of Noah, and their sons and daughters, would have intermarried and redistributed the three (possibly very different) mtDNA types. Mutations would have crept in over time, leading to three “families” of mtDNA. But since mtDNA is almost always passed on maternally, its diversity can actually decrease rather quickly, as Dr. Todd Wood describes in “Four Women, a Boat, and Lots of Kids” (in the latest issue of Answers magazine). Wood writes:

How can different genes in the same person come from different sources? Remember that eight people were on the Ark but only four were women, whom we will assume were not closely related. Right after the Flood, a total of four types of mitochondrial DNA were present among the women of the human population. There were even more types of nuclear DNA among both the males and females. Now imagine how quickly the types of mitochondrial DNA could be lost. If Japheth had one daughter and this daughter did not have any daughters, then the mitochondria of Japheth’s wife would have been lost, but Japheth’s nuclear genes would survive through his sons. In this way, mitochondrial diversity can be lost quickly during a genetic bottleneck, while nuclear diversity can be preserved.

So here’s a hypothesis: during the time between the Flood and Babel, the various ratios of sons and daughters born to the descendants of Ham, Shem, and Japheth could have gradually reduced mtDNA diversity, such that one mtDNA lineage would have became dominant by the time of Babel. Nonetheless, the other lineages could have still survived all the way through Babel, albeit in smaller groups of people. By the time of the dispersion after God confused language at Babel, perhaps mtDNA was primarily from (for example) Shem’s wife, whereas only a few families retained the mtDNA of Ham’s wife. As people left Babel separately, then later intermarried with other people groups, populations would have picked up both lineages, but the families who retained the mtDNA of Ham’s wife—and who, in this example, traveled to southern Africa—would have still kept a much higher proportion of Ham’s wife’s DNA even if some intermarriage occurred. This also fits with the fact that the Khoisan people are isolated hunter-gatherers, and probably have had relatively little contact with other Africans.

Only a few families retained the mtDNA of Ham’s wife.

Of course, this is just a hypothesis, but imagine secular scientists, loaded with evolutionary presuppositions, coming upon a high proportion of Ham’s wife’s mtDNA (the modern version of it, anyway) in the Khoisan people and—using evolutionary assumptions about mtDNA and the dominant evolutionary view of human origins in Africa—concluding that there must have been a great divergence long ago, followed by an eventual partial reunification. They then see that climate change has been hypothesized thousands of years ago, and fit the pieces into a great story of human history, all without acknowledging the Creator or His Eyewitness Revelation.

It could also be a much less exciting story. As Tishkoff suggested, it could simply be that since both major mtDNA lineages are found in Africans, the Khoisan people simply lost most of one lineage over time. This would likewise explain the data without any need to explain a great divergence.

Ultimately, we cannot point to any two distantly related humans and identify exactly how long ago their lineages diverged without using assumptions. For these evolutionists, the assumptions are about 5000+ year mtDNA mutation rates, a common ancestor between apes and humans, origin of humans in Africa, and so forth. For creationists, the assumptions are that we descended from Adam through the population bottleneck of a great global Flood that wiped out all human life except for eight people, and that from there, humanity was rebuilt, with the confusion at and dispersion from Babel another major factor.

Thus, once again, the question is what or whom you put your faith in: the fallible assumptions of mankind or the infallible Word of God, who inspired the writing of true human history?

Further Reading

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Footnotes

  1. Mitochondrial DNA, or mtDNA, is a specific type of DNA that is found in cells’ mitochondria rather than in the nucleus. It forms in a circle, unlike the linear shape of nuclear DNA.

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