Does Genetics Point to a Single Primal Couple?

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April 5, 2010 Tags: Human Origins

Today's entry was written by Dennis Venema and Darrel Falk. You can read more about what we believe here.

Does Genetics Point to a Single Primal Couple?

A Single Primal Couple?

Most Christians who have grappled with the science of genomics (the branch of biology that compares the DNA sequences of different organisms to one another) have done so with the question of common ancestry in mind: do humans share an ancestor with other forms of life, such as chimpanzees?

Here the evidence is very compelling, and reasonably accessible to non-specialists. For example, the human genome has numerous defective genes embedded it, and the vast majority of these defective genes are also present in the chimpanzee genome in the same relative positions with identical mutations. This sort of evidence is easily understood due to its qualitative nature.

A second question, and one that is less frequently explored even by Christians who accept common ancestry, is the issue of human/hominid population sizes during our evolutionary history. Specifically, is the human race descended from one ancestral pair in the recent past? Are we, as C.S. Lewis puts it in his Chronicles of Narnia, the “sons of Adam and daughters of Eve”? Is there genomic evidence to suggest that the human race is genetically derived from a primal pair? Here the evidence is more difficult for non-specialists to appreciate, because it is quantitative in nature.

Genomics can be used as an estimate of population sizes in the past by measuring genetic variation in the present. Genes come in different forms, or alleles: for example, the human ABO blood types are determined by three alleles of one gene. Some genes in human populations exist in hundreds of forms.

The catch, however, is that any individual person can only carry at most two different varieties of any one gene: one from mom, the other from dad. It therefore follows that a large population can pass on a large number of gene forms (alleles), but a population that passes through a population “bottleneck”—where only a small number individuals survive—will fail to pass on most of its genetic variation to future generations.

Attempting to square the Genesis account and common ancestry by positing a literal Adam and Eve who were the progenitors of the entire human race is, biologically speaking, looking for the most extreme population bottleneck a sexually reproducing species can experience: a reduction to one breeding pair.

Is there evidence that such a bottleneck has ever occurred? Dr. Peter Enns has been exploring whether this is even the right question to be asking from a biblical perspective (here, here, here, and here). Here we explore three independent ways of answering the question, this time from a biological point of view.

Method I:

The genetic consequences of a bottleneck required by a literal reading of Genesis 2-3 would be severe: at maximum, four gene-forms (two from each parent) would be passed on by Adam and Eve. Interbreeding in the (necessarily very small) population after the bottleneck would result in the further loss of some alleles due to chance alone. In short, the genetic impact of such an event would leave a stamp on the genome of that species that would persist for tens of thousands of generations as mutations slowly generated genetic diversity.

We can use this information, then, to estimate the minimum number of people that could have existed at any point in time. First we ask how many different alleles there are for a number of genes within the current population. Correcting for the rate at which we know new forms of genes appear (mutation), we can calculate the minimum number of people needed to generate the current amount of diversity. Numerous studies analyzing many different genes all point to a bottleneck. However, these studies are all clear: during the bottleneck, there were several thousand individuals, not two.

Method II:

In earlier posts, we have discussed the fact that DNA segments known as Alu repeats, can insert themselves at various locations the genome. It turns out that the Alu sequence comes in various forms, like different makes of cars—Fords, Toyota, etc. There are several thousand families of Alu.

Consider just one family, which we will call Ya5. Members of this family have been inserted into human chromosomes at 57 mapped locations. If all humans descended from a single pair of individuals, all humans would have each of the 57 elements in pretty much the same locations, since individual members of the family almost never move. However, the human population consists of groups of people who share some insertion points but not others. The multiple shared categories make it clear that although a human population bottleneck occurred, it was definitely never as small as two. In fact, this line of evidence also indicates that there were at least several thousand people when the population was at its smallest.

This method is much different than Method I since it does not depend upon mutation rate, but the answer is similar.

Method III:

A third independent estimate makes use of a concerted research effort called the HapMap project. Humans have 3 billion bits of information in their genomes. (The official term for one bit is a “nucleotide.”) The bits between any two individuals differ at many sites, which is, of course, why we don’t all look the same.

In the HapMap project, one million of these differences have been analyzed by examining something called linkage disequilibrium The technical details are beyond the scope of our discussion, but to give you a feeling for how it works, imagine that you have a gene for blue eyes and a gene for a bent finger, both of which you inherited from your dad. Assume these genes reside in the same “neighborhood” on chromosome 2. Because these genes are close to one another, chances are that if your brother got the blue eye allele from your dad, he would have received the bent finger allele as well. After all they are neighboring genes, both on chromosome 2. Why? Blocks of genes in the same neighborhood on a chromosome are usually inherited together. Alleles that are very close together on chromosomes tend to stay together for many generations before they are “mixed and matched” through a process called recombination.

Now pretend that someone analyzes both your DNA and that of your brother in a double blind experiment. The investigator would, upon examining the results, be able to say, “I’ll bet these two people are related to each other.” And he would be right.

Now picture being able to do this, not for two differences, but for a million differences all at once and not just for two people, but for many people from all over the world. Using this approach, it is possible to tell how many people gave rise to all the prevalent combinations of differences. In short, we can tell if everyone came from just two people at any time in the last 200,000 years. So did we?

No.

This third independent method tells us that everyone alive today is related, but not to a single pair of people. We are related to a population that consisted of several thousand people with their several thousand combinations of these million genetic differences.

Here’s the real point of this. When you have one way of doing a calculation and you get a certain answer, perhaps you are justified in being a little skeptical. Perhaps you made a mathematical mistake, or maybe you made a faulty assumption. However, when you do your calculation using two totally different approaches, using methods with completely different assumptions, and each method gives you the same answer, you become convinced it is correct. Three, of course is just icing on the cake.

So that’s the situation we are in with regard to the human population size in ancient history. There was a bottleneck. There were likely fewer people alive during that time than the number of fans attending a typical NHL hockey game. (We don’t know if they were all together in one village, of course, but the total was small.) However, it was not two people. Our species diverged as a population. The data are absolutely clear about that.

References:

  1. Relethford, JH. 1998. Genetics of modern human origins and diversity. Annu. Rev. Anthropol. 27: 1-23.
  2. Tenesa A, Navarro P, Hayes BJ, Duffy DL, Clarke GM, Goddard ME, Visscher PM. 2007. Recent human effective population size estimated from linkage disequilibrium. Genome Res. 17:520–526. (available free here)
  3. Sherry ST, Harpending HC, Batzer MA, Stoneking M. 1997. Alu evolution in human populations: using the coalescent to estimate effective population size. Genetics 147:1977-1982. (available free here)
  4. http://hapmap.ncbi.nlm.nih.gov/index.html.en

 

 


Dennis Venema is Fellow of Biology for The BioLogos Foundation and associate professor of biology at Trinity Western University in Langley, British Columbia. His research is focused on the genetics of pattern formation and signalling.
Darrel Falk is former president of The BioLogos Foundation. He transitioned into Christian higher education 25 years ago and has given numerous talks about the relationship between science and faith at many universities and seminaries. He is the author of Coming to Peace with Science.

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Savage - #9519

April 12th 2010

And:

“When I spotted Feser’s book, I looked forward to reading a reasoned critique of Dawkins, Dennett, and other writers who over-sell Darwinism into a bloated pseudo-philosophy that supposedly explains everything. Sadly, Feser’s book does nothing of the sort.

“Feser never really defines the “new atheism,” nor explains how it differs from the “old atheism” (whatever that might be!). He describes it only in terms of the popularity of trendy atheist writers like Dawkins, Dennett, Hitchens, and Harris. There’s little consideration of these writers’ actual ideas. Most of the book is a discussion of the ideas of Aristotle and Aquinas, and Feser’s contention that western civ went horribly wrong when it turned away from their philosophies.”

So I will give Feser’s book a skip.


BenYachov - #9524

April 12th 2010

Yes I recognize most of those negative reviews they are from various New Atheists (mostly on Amazon comments section or on the Blogs) who basically didn’t read the book(I did & the only accuracy is Feser does harshly insult his opponents but he backs it up with rigorous philosophical argument.  Strange how for someone who advocates science & experimentation you rely on an argument from Authority in this case instead of testing the hypothesis yourself.  Such faith you have in these people’s unbiased & well reasoned critiques without a hint of name calling. 

Savage you have convinced me of one thing.  Dawkins was right a rational person can’t convince a die in the wool faith-head.  Accept in this case sadly for you I’m not the faith-head.


Savage - #9526

April 12th 2010

You call Feser rational? Look at this piece from a review:

“But the real howlers come with his next two arguments, which are similar. Consider some object, like an electron. According to Feser, in order for the electron to exist from moment to moment, something external must act on it. Something must “keep it going”. This is true he claims because it is not the nature of an electron to “keep going” on its own. Also, in order for an electron to behave in an orderly and consistent way, it must be guided by an external intelligence that provides the electron a “purpose”. Feser speculates that if an intelligent mind was not directing things, then the Moon might zip over to Mars for a bit and then come back. (He really writes that. Page 115.)”


Savage - #9528

April 12th 2010

I forgot to add:  Feser’s “science” is ex recto reasoning of the highest order. How do you rate his philosophical reasoning?


pds - #9531

April 12th 2010

Bilbo #9327,

You don’t have to answer if you don’t want to.  But I was responding to your proposal and the Lewis quote you referenced.


Patrick M - #9545

April 12th 2010

Savage, all of science comes from philosophy.  It is the basis for both science and mathematics.  Any scientist with a decent background in the history of science can tell you this!
http://en.wikipedia.org/wiki/History_of_scientific_method


BenYachov - #9546

April 12th 2010

Savage,
  Quoting persons who know nothing about Aristotle or philosophy & clearly have not read the book but skipped through it is not impressive.  It’s like citing a Minister with a 6th grade education who claims the Second Law of Thermodynamics refutes Richard Dawkins on evolution.  It’s anti-intellectual, unscientific & just sad.  Feser’s conclusion (defended in the previous 114 pages) is based on the thesis “Potency and Act divide being in such a way that whatever is, is either pure act, or of necessity it is composed of potency and act as primary and intrinsic principles.”  Since an Election orbiting Proton can be changed by definition it can’t be Pure Act(only God is Pure Act).  Also Act is a perfection & Being itself is an Act that is either the result of a potency being actualized or by necessity is Pure Actuality.  Thus if the universe contained only one atom because of it’s nature it would need something that is Pure Actuality to maintain it’s existence.  Feser explains & defends this thesis & contrasts them with the Mechanistic Philosophy that excepts the existence of contingent things as mere brute facts because of the various mistakes made by Hume, Locke & Kant.


Unaplogetic Catholic - #9547

April 12th 2010

Bilbo,  (if yo’re still reading)

“But I believe it is assumed in biology that all speciation must involve mutation.”


No, not true.

” The first 99 mutations must already be fixed in the population.  Then an individual pops up with the 100th mutation.  The only way to identify that individual is to do so before that mutation becomes fixed in the population.  Afterwards, I doubt that it could be done.”

That’s not how genetics works.  I think you;re trying to fit a sqare peg in a round hole.


BenYachov(Jim Scott 4th) - #9548

April 12th 2010

Also it is important to contrast the Teleology held by a Theistic Mechanist vs Thomistic Teleology. 

http://edwardfeser.blogspot.com/2010/04/intelligent-design-theory-and-mechanism.html

They are only alike in the same manner Lamarkian Evolution is like Darwin but they are radically different like both Lamark Vs. Darwin.


Savage - #9590

April 13th 2010

“Since an Election [sic] orbiting Proton can be changed by definition it can’t be Pure Act(only God is Pure Act).”

This is perhaps true in your philosophy, but definitely not in Nature. Change your definition and see if you can change the theory of quantum electro dynamics; you are sure to fail. And also proof that only “God is Pure Act”. You are caught in a philosophical “school” where you don’t think for yourself, and thus come up with scientific nonsense like these.

“Also Act is a perfection & Being itself is an Act that is either the result of a potency being actualized or by necessity is Pure Actuality.”

If you agree with Feser’s description of the behaviour of the electron, you are with a group that are definitely not taken seriously by scientists, and can be proven wrong time and again in the physical world; but perhaps not in the philosophical world.


Savage - #9591

April 13th 2010

“Savage, all of science comes from philosophy.”

In the strictest sense of the definition of philosophy, that is true. But that is not what I am arguing. My argument is that the philosopher and the scientist have totally separate operating fields; the scientist describes Nature, and harnessing Nature’s forces correctly, our modern lifestyle came about. What has philosophy contributed to our modern world; nothing. Look how many different “schools of philosophy” are there, and they all differ; at times drastically, whereas the theory of QED, for instance, describes the strange nature of light and matter; yesterday, today and tomorrow.


BenYachov - #9596

April 13th 2010

>This is perhaps true in your philosophy, but definitely not in Nature. Change your definition and see if you can change the theory of quantum electro dynamicsetc…..

I reply: Classic error your confusing physics with Metaphysics.  The philosophy here is making a Metaphysical argument not an argument from physics & it’s true regardless of what physics you hold too.  Be it Aristotle’s own false view of physics, Newton’s physics, Einstein or Quantum physics the metaphysical principles of potency, actuality, essence, & the four causes all apply.  The problem is you don’t think for yourself but mindlessly believe the knownothing cretins over at RichardDawkins dot net where you lifted your original criticism of Feser.  Nice try.

Clearly you are some sort of undergraduate Savage because this is a sophomoric mistake.  Clearly you don’t possess the education to know the difference between a scientific theory of physics vs a Metaphysical demonstration. Pathetic.


BenYachov - #9598

April 13th 2010

>If you agree with Feser’s description of the behaviour of the electron, you are with a group that are definitely not taken seriously by scientists, and can be proven wrong time and again in the physical world; but perhaps not in the philosophical world.

I reply; Your ignorance of science, philosophy & the history of science clearly knows no bounds.  Clearly you are unaware of “Physics and Philosophy: The Revolution in Modern Science by Heisenberg”  where he tentatively endorsed the Aristotelian concepts of Act & Potency QUOTE"The probability wave of Bohr, Kramers, Slater… was a quantitative version of the old concept of “potentia” in Aristotelian philosophy. It introduced something standing in the middle between the idea of an event and the actual event, a strange kind of physical reality just in the middle between possibility and reality.“END QUOTE Feser does a whole post on it on his blog

http://edwardfeser.blogspot.com/search?q=Heisenberg


BenYachov - #9599

April 13th 2010

My you are a tower of ignorance my friend.  Indeed u are well named since u have the ignorance of a Savage.  Also rather then think for yourself you would rather rely on the ignorant opinion of some anonymous fellow called Vagavond7 over at the Dawkins forum or some ignorant pleb named Diogenes(google shows me this is where you lifted one of your quotes & two people used them verbatum).  Of course in the Comments box over at Amazon some bright fellow named S. Parrish takes Diogenes to school.


BenYachov - #9600

April 13th 2010

>My argument is that the philosopher and the scientist have totally separate operating fields;

I reply: You can’t even comprehend the implication of your own statement.  If you really believe the above then by your own admission your criticisms of Feser in post# 9590 is invalid. Again it’s like you are saying the Andromeda Galaxy doesn’t exist because you can’t observe it under your microscope & no matter how many times it’ s explained to you Andromeda is a macro object & not a micro one you merely plead the undeniable success of microscopes in detecting microscopic objects & ignore the obvious category mistake on your part.
This scientism fallacy keeps dogging you.


Savage - #9601

April 13th 2010

“The problem is you don’t think for yourself but mindlessly believe the knownothing cretins over at RichardDawkins dot net where you lifted your original criticism of Feser. “

These were critiques of Feser’s book. It does not matter where it was written, now does it? You did not attempt to refute the critics but instead attacked them personally, calling them “knownothing cretins” and “New Atheists”.

Before I buy a book, I first read reviews of it, and then decide. Having read the reviews of Feser’s book, I would most certainly not buy it or even read it. (Look at his “science”, for crying out loud!) But because you call anybody who disagrees with you names, does not in any way make your premises true, nor Feser’s.


BenYachov - #9602

April 13th 2010

> the scientist describes Nature, and harnessing Nature’s forces correctly,

I reply: But the problem is without philosophy you can’t claim “Science disproves religion” nor can you claim “Science proves religion” nor can you even say “Science neither proves no disproves religion”.  You can say fish swim & my Xbox is broken.  That’s it.  Yet you pretend otherwise & contradict yourself in the process.  You cited Camus before?  Like most Existentialists(be they Atheists or Theists) he was a notorious anti-rationalist.  That was the best you can do?  The rational metaphysics of Aristotle which helped birth modern science & you cite an anti-rationalist?  Yikes!!!! 

The thing that breaks my heart is not so much you deny God savage.  But you deny the very reason, logic & sciences you claimed to have adopted in His place.  Thus in the end you have nothing.


Savage - #9603

April 13th 2010

If you think I do not know the difference between physics and metaphysics, you have not paid attention what I wrote before. But for the record, here is my understanding of the two widely separated disciplines.

Physics is the study of Nature. It is the study of the physical, measurable Universe we live in. It describes matter, energy, gravity, etc. etc.

Metaphysics the study of theology and ontology.


BenYachov - #9604

April 13th 2010

>These were critiques of Feser’s book. It does not matter where it was written, now does it? You did not attempt to refute the critics but instead attacked them personally, calling them “knownothing cretins” and “New Atheists”.

I reply:  It does matter since how do u know either of these people are qualified in the area of either philosophy or science.?  A smart move would have been to read a PROFESSIONAL academic review. duh!  What you don’t believe in academia?  It’s not hard.  Also I did refute u & it’s not my fault you are reading anonymous cretins & not peer reviewed academics.  I


BenYachov - #9605

April 13th 2010

>Metaphysics the study of theology and ontology.

I reply: Metaphysics is the study of being & what is beyond physics it doesn’t have to have anything to do with theology,  What you never heard of metaphysical naturalism?  Sheesh!


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