Swamidass addresses many topics, but here are some key concepts of particular interest to me.
Key Concepts
1. Genealogical ancestry is not genetic ancestry
2. The term "Human" has many definitions, in various context.
Addressing (1), "genetics" refers to the passage of bits of replicated genetic material (DNA), from parents to offspring. "Genealogy" on the other hand, is the connection by lineal descent off parents to their progeny.
This becomes when one considers the following statements:
- Genetically, you inherit, on average, 50% of your cell's material from your mother and 50% from your father.
- You are a descendent of your mother and you are a descendant of your father.
If you notice the difference, one is quantitative and statistical. The other is simply factual.
You inherit, on average, 25% of your cell's material from each of your four grandparents, but you would not say that your grandfather is your "1/4" grandfather. He is simply your grandfather. You came from him and he is your ancestor.
Now, Swamidass wants us to think about this further. Generally speaking, everyone has 2 parents, 4 grandparents, 8 great-grandparents, etc.
Going back 10 generations means you double this 10 times. 2x2x2x2x2x2x2x2x2x2=1024. That doesn't seem too shocking. Going back 20 generations gets you to 1024x1024 which is about a million ancestors. That's a lot! Going back 30 generations gets you to about 1024 times more, or about 1 billion ancestors. At some point the problem becomes obvious. Assuming about 30 years between each generation, that only accounts for 900 years. That's more people than there were on earth that long ago. The solution of course is that we all have a lot of shared ancestors.
In fact, if you go back far enough, we all have exactly the same set of ancestors!
Consider a time 5000 years ago, equating to roughly 200 generations. The population of the earth has been estimated to be 14 million people in 3000 BC. That's a lot of people, but of course, not all of them got married and had children. Some did, but their children died, or they had a few children, but those children, when they grew up and got married remained childless. In other words, some lineages died out. Some of those 14,000,000 people have no living descendants today.
Now we can calculate the population growth rate, and by my figuring it works out to about 1.27% per year. Every year, for each 1000 people, about 13 children will be born and survive. A married couple might have about 30 years during which they might have kids, so over those 30 years, 390 children will be born to those 1000 people. That means the vast majority will not have children. And if you factor in that most families had multiple children, that increases the number of people with no descendants. If each fertile couple had on average 3 surviving children, then only about 130 people out of 1000 would leave all the descendants. This works out to about 1,800,000 people who would be ancestors of those living today. Going back to 10,000 BC, it works out to about 130,000 ancestors shared by all humanity. (Now, these are my own calculations; if I get a copy of Joshua Swamidass's book, I might be able to get his more informed numbers.)
The upshot is that although we can have 1000's of ancestors, and therefore genetic contributions of many different parts of the world, it still leads back to a relatively small number of shared common ancestors.
So how can there be so much diversity in a world in which we have the same ancestors? That's where genetics come in to play. We each inherit different bits of DNA from each ancestor, in different percentages. Just like siblings of the same parents can look very different from each other, different groups of people can look very different from each other.
Take Abraham as an example. He lived about 4000 years ago. Many Jews and Arabs count him as their ancestor. But countless more people actually descended from him, from groups that broke off from the Jews and Arabs and migrated to other parts of the world. Most will not even know that they have Abrahamic ancestry. But those people could say, "I am a descendant of Abraham." And that would be just as true a statement for the person who had only 1 ancestor out of a 1000 who descended from Abraham as it would be for the person who had 900 out of 1000 ancestors descended from Abraham.
Swamidass calls this group of shared ancestors the Most Recent Universal Genealogical Ancestors (MRUGAs). Another related term is the Identical Ancestors Point, which is the most recent point in a given population's past where each individual then alive turned out to either be the ancestor of every individual alive now or has no currently living descendants.
So, the point of Swamidass's argument is that one of those couples is Adam and Eve.
For everyone alive on earth, as long as Adam and Eve lived before about 5,000 to 15,000 years ago, we can all say that we descended from Adam and Eve.
People Outside the Garden (of Eden) - POTG
Now we go on to point (2) above, and this is important. There might have been other couples alive 5,000 to 15,000 years ago, right along side Adam and Eve. And if any of those couple have any living descendants, we are their descendants, too!
In Swamidass's language, these are People Outside The Garden, what he calls POTG.
So were there other couples living outside the Garden of Eden? If we look back 5,000 to 15,000 years ago, the scientific position would be a very strong, YES.
Biblically, we could say that Cain married one of the POTG. That's were he got his wife. Some Christians would be comfortable with that, and others would not be. Either way, it can raise a lot of questions about what it means to be human, original sin, and atonement.
Now, 15,000 years ago, it seems that any living POTG would certainly be fully human in every regard that is normally considered from the scientific perspective.
Problems with a very ancient Adam and Eve
But what about 50,000 years ago, or 100,000, or 200,000 years ago.
The further back in time one goes, the smaller the set of Identical Ancestors there are, but so far, genetically speaking, scientists contend that the number never drops below a few thousand. Swamidass calculates that the point in time that would support the idea of an original couple would be more than 500,000 years ago. Even this far back, the population would have been at least several thousand, but the argument can be made that all of the other lines of descent eventually died out except for those of one couple, Adam and Eve. Let's designate this view the single ultimately-successful breeding pair view.
Adam as Heidelberg Man
William Lane Craig follows the extreme end of this, pointing to Adam as a "Heidelberg Man", that is a member of the species Homo heidelbergensis. He contends that along with Homo sapien sapiens (fully modern human beings), the Neaderthal and Denisovans were also descendants of Adam and Eve. In this scenario, Adam and Eve lived 500,000 to 750,000 years ago.
What I see as a major problem with this view is that it is allowing genetics to drive the date, not the Biblical text. And the genetics will keep changing. If one could go back in time 100,000 years and sample the DNA of thousands of individuals around the world, there would be a much larger data set than we currently have. In that larger data set, more divergent individuals would be found and the date of common ancestry would have to be pushed back even further. For example, we might find DNA of Homo Erectus or Homo Antecessor pushing the date back past one million years ago. So this view can only say that God choose one couple to eventually become the ancestors of all people on Earth.
Not only does this seem to change the primary meaning of the text, but it opens up the date when Adam and Eve lived to constant revision. All it might take is one more fossil find from which ancient DNA is extracted to identify yet another contributor to the human gene pool. That contributor's DNA could be just slightly more diverged than Neaderthal or Denisovan DNA, pushing back the date of a single ultimately successful breeding pair (Adam and Eve) by tens or hundreds of thousands of years.
POTG as non-humans
On the other hand, Craig contends that the POTG would not have the "humanness" of Adam, Eve, and their descendants. They would not be in the same category as Homo sapiens, Neanderthals, or Denisovans, but rather something different. They would not be accorded the dignity of "bearers of the image of God".
For Craig, whenever Adam and Eve lived, he can acknowledge that there were POTG, but contends that they were not of equal humanness to Adam and Eve.
Reasons To Believe takes this same stand, with variation. RTB excludes Neanderthal and Denisovans as "image bearers of God", instead drawing the line at archaic modern humans, possibly including Homo sapiens idaltu (c. 160,000 ya).
The Ages of Joy model follows Craig and RTB, but further excludes archaic Homo sapiens, instead looking to a fully modern human originating less than 100,000 years ago, and probably closer to 75,000 years ago. As such, AOJ sets a slightly higher bar for what constitutes Imago Dei humanness.
The problem with a very recent Adam and Eve
Although it is Swamidass's calculations that provide the scientific framework for Craig's position, Swamidass himself prefers a much more recent date of just several thousand years.
This starts raising a lot more questions.
The definition of POTG
Were the people outside the garden "humans"?
This is confusion (2) above. What is a human? In much of scientific literature, the word human is taken to mean any member of the genus Homo. This includes Neanderthal, Denisovans, Antecessor, Heidelbergensis, Erectus, and others. It's a broad category. A technical term often used for modern humans is Homo sapiens sapiens. But, the distinction between "Early Modern Humans" and "Modern Humans" is a bit of a grey area. Sub-species get assigned like Homo sapiens idaltu which are sometimes equated with Early or Archaic Modern Humans. These are sometimes referred to as morphologically primitive anatomically modern humans. So are they modern, or are they primitive?
The homo sapiens idaltu where more robust (stockier) and had a more protruding but smaller chin. But less so than a Neanderthal.
In addition to looking at physical anatomy, archaeologists are concerned with the artifacts that indicate the kinds of behavior these species engaged in. The search is for clues that denote "modern human behavior". This explores the gap between anatomical and behavioral modernity.
Humanness as behavioral modernity
Scientists talk about advanced cognitive behaviors including: abstract thinking, planning, innovation, and appreciation of symbolism.
Humanness as the Image of God
Christian theologians talk about a different concept called Imago Dei or the Image of God, and have debated the meaning for thousands of years. One way of breaking the debate down is to think of these three categories: Capabilities, Occupation, and Destiny.
Capabilities = things that distinguish people from animals
Humans speak, reason, relate and are morally responsible before God.
Occupation = we have an occupation and a mission to fulfill in this world, given by God.
Human beings are called to express God's rule and management of the world.
Destiny = we have the destiny of bearing God's image
Humans are created to be adopted siblings of Christ, coheirs of his inheritance, members of the family of God.
As you can see, the way scientists distinguish human from animal and the way a Christian would distinguish a human from an animal are quite different. Bridging the gap is difficult.
So, were the POTG at the time of Adam and Eve real people?
The Ages of Joy model looks at all three aspects of the Image of God.
1. Were the POTG morally responsible to God?
2. Were the POTG called to express God's rule and management of the world?
3. Were the POTG created to be adopted into Christ and to live forever?
Are you a human? The ultimate "CAPTCHA"
I think that POTG probably fail on all three accounts, especially going back pre-100,000 years ago.
Capabilities Test
A Homo sapiens idaltu living 160,000 years ago may have had a language, perhaps even a Click language, they certainly had relational capacity with one another, and they would have had some ability to reason. Many mammals can solve various kinds of puzzles and remember sequences of steps. Chimpanzees can even learn sign language and teach it to one another. (I need to cite my sources on these claims)
But it is not clear that they would have been held morally responsible to God. This implies a developed conscience. Even children living today don't reach the "age of moral responsibility" until long after they learn to do many complex things. That fully mature members of the family Homo sapiens idaltu had a developed conscience cannot be shown from any artifacts yet found.
POTG may have been living like clever children from a moral reasoning capacity point of view. Perhaps Cain ventured into the land of Nod to take a wife for himself among those who in all other ways seemed similar to himself. Certainly they were not beasts. Genetically they were compatible. Yet his wife and her people would have held a simplistic, survivalist view of life. They were pragmatic and utilitarian with no ability contend with questions of morality or ethics or issues of good and evil. Their concept of "right and wrong" was limited in scope to expected tribal norms - submission, obedience, cooperation. The rules were all black and white, traditional, unquestioned. Like a pack of wolves or a herd of elephants there was group memory, group expectations, group rules. The rules and thought patterns might be complex, but there was no sense of guilt or shame, only of fear. No sense of a clear conscience with the hope of approval, only a sense of acceptance with the reward of protection. Share and share-alike. Tit for tat. Mechanist rules. Modern human behavior under duress can degrade to amoral utilitarianism, but for the POTG, they could not rise above it.
In enters Cain. He fears the POTG because he is not going to play by their rules. He is given a mark by God. A mark the POTG fear. He marries one of them. She is submissive, obedient, cooperative. She is not Cain's equal. She is not like Eve. For Adam, God did not select a mate from among the POTG. But Cain's children rise above their mother. They are like their father Cain. They learn right and wrong. They have a human spirit and their eyes are open, knowing good and evil. And they are under God's judgment for how they live. Cain builds a city in the land of wandering. His descendants remain collected for a time, perhaps intermarrying with Seth's children on occasion. Perhaps Seth's line remains more pure. Perhaps Cain's line migrates throughout the world. Back to Africa. Into Asia and Australia. Into Europe.
Occupation Test
When did humans begin to rule and manage the world? Out-of-Africa migrations have been occurring for hundreds of thousands, if not millions, of years. But all of them proved ultimately unsuccessful until somewhere around 80,000 to 60,000 years ago.
Destiny Test
This is the most crucial test and the one most clearly tied to the identity of humans. Humans are those creatures which God intended to be the adopted siblings of Christ. More specifically, we are God's children. The Bible clearly calls Adam the Son of God. This is the same appellation applied to Jesus, who is the incarnation of God the Son. In this sense, all real humans must descend from Adam. Therefore, the POTG are by definition, not Homo sapiens filio dei, that is Homo sapiens sons of God. However, a careful point must be made. The POTG may be called Homo sapiens sapiens in a true sense. Or if we consider the term Homo sapiens sapiens to be identical to Homo sapiens filio dei, then we would call the POTG Homo sapiens sapiens minus, or Human Beings- for short. That is, the POTG lack something. That something might be difficult to distinguish from genetic, fossil, or artifactual evidence alone. What we could say however, that the offspring of unions between Adam's children and the POTG would be offspring of Adam, and therefore Homo sapiens filio dei, or true Human Beings, no '-' required.
The doctrine of the Incarnation of Christ might help us think about this. Jesus Christ is Fully Man and Fully God. Adam is Fully Homo sapiens sapiens and Fully Homo sapiens filio dei. That is, Adam is fully a biological anatomically and behaviorally modern human but also fully a son of God. The POTG, even if biologically human, were not fully human in the same sense as Adam. And that makes all the difference. The POTG weren't facing heaven or hell as an ultimate destiny.
So, in this view, admixture begets identity. Whatever the something is that is necessary to make the leap from non-destined to destined, can be conveyed by heredity. Now there are two kinds of heredity that we can consider. One is biological, and the other is genealogical. In the first kind, we might consider that Adam and Eve conveyed some kind of genetic advantage loaded into their DNA. In the case of the genetic advantage being dominant and highly selected for, it could spread rapidly through an admixed population and become "fixed", that is genetically permanent and ubiquitous, within a few generations.
In the second kind, genealogical heredity works kind of like royalty. Any amount of "royal blood" can convey royal privilege. This is the model I prefer and I link it to God's spiritual adoption and conference of an immortal spirit upon all those who descend from Adam and Eve. Thus the "destiny" of mankind spread rapidly among POTG through admixture. It also spreads more strongly than DNA. It is not subject to dilution and selection, but rather is indelible. God keeps track. What about the offspring between a descendant of Adam and a Neanderthal? From this particular genealogical point of view, they would be considered spiritually-destined human beings, and I would expect God to judge them as such, while also considering any limitations they may have had. God is merciful and just, and He is not mocked. Today, most or all people have some Neanderthal DNA. This does not rob us of our destiny nor our responsibility before God.
An important part of this test is the assertion that there is ample evidence to support the notion of a back migration into Africa during or shortly after Adam and Eve's lifetime. This is the idea of a Back to Africa Migration immediately following the Out of Africa Migration. There is some possibility that Adam and Eve and their descendants were largely confined to a refugia in the area near Eden for a time before the migration corridor to Africa opened up again. Furthermore, admixture within Africa may have happened completely and thoroughly within generations, possibly within a few thousand years or even less. That these African humans are Sons of God remains true, even if genetically they retain much of their non-Adamic DNA. This is plausible, given that the DNA of the Africa POTG is already tuned for African climate and ecology and will be strongly preserved in that environment. However, the Son of God factor can also be thought of as highly conserved and advantageous and is quickly fixed among the population. This can be true in either model of heredity, whether is comes as a bit Nuclear DNA or as a royal identity attached to being God's son or daughter through Adam.
We can assert strongly that there are no groups of humans in the world that are so isolated as to not be of the line of Adam both genealogically and genetically. I suspect that by the time that the Neanderthal and Denisovans went extinct, so too had all non-Adamic-related groups of homo sapiens.
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