Genetics is a topic I have avoided here for one simple reason: I
am not a geneticist.* But I could not help but to comment on
some of the recent reactions to an article by Dennis Venema and
Darrel Falk, entitled
Does Genetics Point to a Single Primal Couple?
authors argued therein that data from modern
genetics do not corroborate the traditional biblical postulate
of a single, primal couple (i.e. Adam and Eve) who gave rise to
the world's population. National Public Radio (NPR)
on the controversy, citing Dr. Venema from an
interview. Responses from various evangelical camps have been
predictably adamant, and while
tried to focus on a scientific response,
of my post today—skewed the scientific data and questioned Dr.
By way of preface, I am aware that many of you side against
on this topic, and would prefer that I stick to
geological issues. So I want to be clear that my aim is not to
persuade you otherwise, necessarily, but simply to promote
critical discussion (to the exclusion of some fruitless
arguments). Since a firm position on the historical Adam is so
treasured by many, it is vital to maintain fairness all around.
Does genetics point to a single primal couple?
Although Drs. Venema and Falk reject the historicity of Adam and
Eve** on biblical and scientific grounds, the purpose of their
article was not to wrestle exhaustively with that evidence. From
what I gathered, the article could be summarized quite simply:
The existence of a primal couple can be
discussed apart from the question of common descent
(i.e. human evolution). Christians are not the only ones
interested in the original population size of the human
race, and geneticists have devised several independent
methods by which to estimate that number. Three of those
methods (discussed here) point to a population bottleneck in
human history, but of several thousands individuals—not two.
The existing genetic data, therefore, do not corroborate the
traditional biblical picture. Any model that
presupposes that picture must account for this evidence.
It would be misleading, therefore, to claim 1) anything from
this article about the authors' motives or
presuppositions with respect to human evolution; 2) that the
authors rest arbitrarily on 'evolutionary assumptions' and
ruled out a priori the existence of Adam/Eve; and 3)
most importantly, that a refutation of this article lends
positive support to the historical Adam/Eve.
ICR skirts the issue, adds to the clamor
At the risk of exposing my bias, I want to reiterate that I
highly appreciate the clarity and cordiality with which Dennis
Venema (and others at Biologos) have presented their respective
positions. As a non-specialist in biology, I have been
frustrated by 'experts' on all sides so desperate for
concurrence that they overlook pivotal, looming questions from
their audience. A recent article by Brian Thomas, entitled
Claims Genetics Disproves Historical Adam
, exemplified that
Mr. Thomas begins with a threefold objection to Dr. Venema's
claim that genetic evidence falsifies the hypothesis that humans
could have derived from a single couple:
"First, it relies on the presumption of
"evolutionary history," not scientific data. Second, the
idea that an initial group of 10,000 humans evolved from
primates is mathematically impossible. Third, a descent from
Adam and Eve actually does explain the patterns in modern
Seemingly, Mr. Thomas cannot distinguish between scientific data
and scientific theories built to explain those data.
Nonetheless, it is rather disingenuous to dismiss an argument
because the data on which it rests require some
interpretation. To be consistent, we would then have to reject
scientific argument. Lastly, Dr. Venema's case is
not without assumptions, but "evolutionary history" is not one
of them, as we shall see.
"Shouldn't such a person at least attempt
to examine the genetic possibility of an Adamic ancestry
before completely ruling it out?"
Caricatures are never helpful. Not merely because they are
false, but also because they provoke hostile emotions without
warrant. If Mr. Thomas had so much as clicked Dennis Venema's
name at the top of the Biologos article (which I'm not sure he
read), he would have found the 5-part series entitled
From Intelligent Design to BioLogos
. It is very misleading
to claim that Dr. Venema has never considered "genetic
possibility of an Adamic ancestry".
Method I – Can total genetic diversity arise from a single
pair in ~6,000 years?
The first method cited by Venema and Falk considered the origin
of genetic diversity in the modern human population. They
"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."
To which Dr. Venema added in the NPR
"You would have to postulate that
there's been this absolutely astronomical mutation rate
that has produced all these new variants in an
incredibly short period of time."
But Mr. Thomas responds by appealing to a false premise:
"Evolutionists assume that all genetic
differences between individuals resulted from
mutations...But if Adam was created with DNA variations,
then one would not have to postulate astronomical mutation
They assume that all
genetic differences result from
mutation? I don't think this is accurate. Regardless, I wonder
what kind of DNA variations Mr. Thomas envisions within Adam's
genome. As the Biologos article explained:
"At maximum, four gene-forms (two from
each parent) would be passed on by Adam and Eve."
An individual genome cannot carry more than two forms of any
gene, meaning that the maximum 'created' diversity would entail
complete heterozygosity in each parent. Since the Biologos
article stated this fact at the outset, Mr. Thomas's argument is
again without foundation.
A more quantitative response came from Dr. Robert Carter at
Creation Ministries International (CMI),
measured rates of mutation are much higher
than those measured indirectly
by comparing the human and
chimpanzee genomes. Mr. Thomas seems to have based much of his
critique on the CMI article, with investigating further. Dr.
Carter writes, for example, that:
"The mutation rates used in the
calculations generally depend on assumptions of common
ancestry...Measurable mutation rates are generally
several orders of magnitude faster than those used in
evolutionary studies. Using a measured rate would shrink the
size of the bottleneck population." (emphasis added)
Using a higher mutation rate to estimate the original human
population would indeed reduce the size of that population—on
this point, everyone agrees. But Dr. Carter does not cite any
studies where mutation rates in the human genome vary by several
orders of magnitude, depending on the technique. So I decided to
investigate. My brief search yielded a highly collaborative
Conrad et al. (2011)
in Nature Geoscience
reported "the first direct comparative analysis of male and
female germline mutation rates from the complete genome
sequences of two parent-offspring trios":
"The sex-averaged germline mutation rate
estimates we derived agree very closely with three other
recent studies focusing on sex-averaged mutation rates in
the most recent generation. Averaging across these four
studies gave a more precise sex-averaged mutation rate of
1.18 × 10−8 [per base pair]...which is less than half of the
frequently cited sex-averaged mutation rate derived from the
human-chimpanzee sequence divergence of 2.5 × 10−8. These
apparently discordant estimates can be largely reconciled if
the age of the human-chimpanzee divergence is pushed back to
7 million years, as suggested by some interpretations of
recent fossil finds..."
Mutation rates can be measured directly by comparing parent and
offspring genomes (as in this study) or by dividing the number
of genetic variations between species by the estimated years
since their last common ancestor. Based on the references cited
within the article, previous estimates of human germline (i.e.
passed on through reproduction) mutation rates varied by a
factor of three
—not orders of magnitude. Moreover, the
uncertainty was due not to conflicting results so much as pricy
technology and limited data, as well as variable estimates for
the last common ancestor between humans and chimpanzees (4–7
Drs. Venema and Falk did not rely on "evolutionary assumptions"
therefore, since measured mutation rates are comparable to, if
than, those estimated from the postulated
timeline of human evolution. As far as I can tell, Dr. Venema's
original point still stands: our current understanding of
genetics suggests that the original human population was much
larger than two, and lived much longer ago than ICR would have
Fuzzy population genetics?
The second objection made by Mr. Thomas seems to be rooted in a
complete misunderstanding of population genetics and evolution.
He argues that it would be "mathematically impossible" for a
population of 10,000 humans to have "evolved from primates".
Since humans are themselves primates, I believe the problem is
also rhetorical, and question whether Mr. Thomas has an accurate
view of human evolution.
For one, the several thousand individuals being discussed
constitute a bottleneck
in human history—not an original
population that somehow received "human-like mutations", as Mr.
Thomas puts it:
"About 700 million information-packed DNA
differences exist...between humans and chimpanzees. Each of
these changes would need to become "fixed" into the whole
population of primates in order to transform them into
Are each of these DNA differences truly "information-packed"?
Many of them are neutral point mutations, found in pseudogenes
or genetic redundancies. Before I address the issue of
"transforming" humans, consider the following hypothetical:
"But even if a single human-like mutation
fortuitously occurred in both members of a reproducing pair,
it would have virtually no chance of spreading to all 10,000
"emerging" humans. Instead, through interbreeding with
non-mutants, the mutation would diffuse and disappear after
only a few generations."
genetic signatures unique to humans are
supposed to have arisen through a rather active force called
natural selection—not the "fortuitous" insertion to and
diffusion throughout the entire hominid population. Furthermore,
it is strange to refer to 'mutants' and 'non-mutants'. Every
human offspring contains several dozen mutations not found in
their parents. We are all mutants! As long as any population
survives with time, there will be thousands to millions of
mutations that define the genetic diversity of that population.
The extent and nature of that diversity give clues as to how
large and diverse that population was in history.
Lastly, genetic drift is sufficient to explain the sporadic
introduction of new alleles (arising through mutation) into a
large population of early humans. Conversely, the chance
of alleles through genetic drift is only
exacerbated by inbreeding that would necessarily occur following
a 2-person or 8-person bottleneck (Adam and Noah, respectively).
Adding 'biblical' parameters
The final objection offered by Mr. Thomas can almost be termed a
tautology. He assures his readers that assuming biblical
parameters, modern genetic data really are
with the young-Earth picture. But adding no relevant
information, his argument appears rather to be an appeal to his
starting position. He begins by citing that "all people are 99
percent genetically similar"—a fact never disputed by either
party but seemingly intended to make genetic variation in humans
small. Consider that when citing the differences
between human and chimpanzees, he used an absolute number
instead: 700 million. He continues:
"For example, any Vietnamese is 99
percent genetically identical to any Ethiopian. Of the one
percent DNA sequence difference between the two, the large
majority is shared by all within their ethnic group, whether
Vietnamese or Ethiopian. A small minority of that one
percent is unique to each individual person."
As I recall, the genetic variation within human subpopulations
can exceed that between individuals
of different ethnic
groups (making categories of 'race' a cloudy topic in biology).
It may range from ~98% to nearly 100%—but what does this add to
the discussion? The fact remains that total genetic diversity in
humans, even if limited to variations that necessarily arose
, cannot be accounted for by a single couple
living less than 10,000 years ago.
Mr. Thomas concludes by promoting the
of Dr. Robert Carter at CMI, which, although novel and
possibly deserving of our consideration, is not without serious
challenges and is hardly conclusive. Perhaps I have missed
something important, but the assessment offered by ICR regarding
the historical Adam controversy seems to be premature at best,
and misleading at worst. I pray that discussion might continue
with more substance and integrity for the sake of all
non-experts at the mercy of respectable Christians in the
*I am not an expert in genetics, but I know a few. So I am
deferring partly to their expertise and input, which I highly
**As a specially created couple from which all humans today
could trace their lineage.