Interpreting the DNA Data and the Book
of Mormon [1]
By John A. Tvedtnes
Part 2 of 3 — Differing Views
Editor’s Note: This is
the second of a three-part series that interprets the recent DNA
data concerning peoples who settled the Western Hemisphere. Part 1 gives a background on
the controversy, as well as thoughts on how the DNA data could
confirm Book of Mormon accounts rather than disprove them.
A very different debate than the one described in yesterday’s
article has arisen over haplogroup X. In a 1997 letter to the
editor of the American Journal of Human Genetics, geneticists
Nestor O. Bianchi and G. Bailliet tried to clarify a misunderstanding
that led to an ongoing disagreement about the nomenclature used
to denote Native American mtDNA haplotypes. [2] They noted that they had “detected the presence
of 8-10 founder mitochondrial haplotypes in extant Amerindian
populations.” They also write that “approximately 4% of the haplotypes
reported by Torroni et al. (1992) in Amerindians did not show
any of the markers characterizing the four founder haplotypes”
and were thus classified as “others” on the assumption that they
resulted from Caucasian admixture.
“We had provided evidence showing that many of these ‘other’
haplotypes were in fact founder Amerindian haplotypes, and had
used the letter ‘E’ to identify this haplotype,” though Easton
et al. “changed the letter ‘E’ to ‘X,” they continue. The authors
note “that we have found the X8 haplotype in 6 of 41
Sioux individuals studied” and add that “there are still important
gaps in our knowledge of the biology of mtDNA.” “We believe that
most of the disagreement among different groups of researchers
working on mtDNA is due to the eagerness to use mtDNA beyond the
limitations of the method. If the aforementioned findings are
confirmed by other groups, the chronologies of human evolution
that are based on mtDNA will need revision in the future.” [3]
In a response that appeared in the same journal, Peter Forster
et al. acknowledged that Bianchi and Bailliet were the first to
identify a fifth Native American founder mtDNA haplotype, generally
called X, but discount some of their other findings and note that
Bianchi and Bailliet grouped all of the “other” mtDNA together
in this newly-discovered lineage. They also suggest that the haplotypes
denoted X6 and X7 by Easton et al. are really “mixed bags of reverted
C and D types, and do not correspond to group X of Forster et
al.” The writers also disagree with the conclusion that substantial
revisions of conclusions based on mtDNA will be required. [4] This is but one issue among many where geneticists
disagree.
A further controversy may be ignited by a 2001 report on a
study of mtDNA variation in 38 Kets and 24 Nganasans living north
of the Yenisey River Basin and the Taimyr Peninsula in Siberia
that compared the results with data previously obtained for 59
Kondinski and 39 Sos’vinski Mansi. Ten European-specific haplogroups
were detected, along with four Asian haplogroups (A, C, D, and
Z), three of them also known in Native Americans. The study concludes
that “Specific features of the haplogroup geographical distribution
along with the results of phylogenetic reconstruction favor the
hypothesis of the genetic trace left in Trans-Urals and the adjacent
Siberian territories by early migrations from the Near East.” [5]
Y-Chromosome
DNA
While all humans inherit mtDNA from their mothers, only males
inherit Y-chromosome DNA from their fathers and the portion tested
represents only 1.5% of the human genome. (Only 2% of the mtDNA
genome is sequenced to determine ancestry.) Consequently, less
research has been performed using the men-only genetic markers,
and the number of Native American men sampled for Y-chromosome
data is only half the number of Native Americans tested for mtDNA. [6]
One such study, reported in 1994, looked at 31 Mixtec and Zapotec
males from southern Mexico, in the region generally held by Latter-day Saint scholars
to be the location of most Book of Mormon events. Six of the 11
haplotypes detected had been previously described for other human
populations, while 5 were new. (Each of the newly-discovered haplotypes
was found in a single individual and all five were considered
by the researchers to be new mutations.)
One of the previously-attested haplotypes (18) “was most prevalent
in Native Americans,” and was found in 45.2% of the samples from
southern Mexico, though it was also known “at low frequencies in Italians,
English, and Ashkenazi and Sephardi Jews, and in some Caucasian
and African populations from South Africa.” Haplotypes 13 and 63 represented 12.9% of the southern
Mexican samples. “Haplotype 13 was previously reported at low
frequencies in Italians, Ashkenazi Jews, and Czechoslovaks,
but was present in 19% of South African Indians,” while “Haplotype
63 was much rarer, having been described as a ‘new’ haplotype
in only two Egyptians, one Ashkenazi Jew, and two Indians
from South Africa.”
Haplotype 15 was found in only one of the Mexican samples.
Though the researchers considered the possibility that it “might
also be a founding haplotype,” they noted that “it has not been
observed in preliminary analyses of Asian subchromosomes,” though
it is “the most common haplotype in European populations, with
a frequency greater than 40% in some populations from Spain,”
leading to the conclusion that “its presence in the Mixtecs from
the Alta and in the Zapotecs is likely due to recent Caucasian
admixture,” i.e., from the Spanish conquerors of Mexico. [7] Latter-day Saints, of course, would find the Jewish
connections the most interesting.
The authors of a 2003 study noted a mutation 242 that gave
rise to Y-chromosome haplogroup 10, [8] which they hold to have occurred in Asia prior to the arrival of immigrants to the New World, since it is attested in frequencies of 0-17%
in samples drawn from Central Asian, Indian, and Siberian populations
(1,935 individuals). Of interest is the fact that among the highest
frequencies is 14% attested in samples drawn from the Middle Eastern
“Arab/Bukhara” group.
A 1999 study examined Y-chromosome markers “of 2,198 males
from 60 global populations, including 19 Native American and 15
indigenous North Asian Groups.” The researchers detected “14 unique
Y-chromosome haplotypes,” of which 9 were attested in Native Americans.
Of these, two (1G, 53.5% and 1C, 35.8%) were the most common in
the New World and also attested in Asia, including Siberia and,
“Interestingly, the second highest Old World regional frequency
(37.7%) of haplotype 1C was found in our composite European sampler,
in which it demonstrated a north-south trend with a maximum frequency
(68.8%) in the British.” [9] So while it may have entered the New World from Asia, it could just as likely have come from northern Europe, i.e., from the same region considered by some
researchers to be the source of mtDNA haplogroup X.
Of particular interest is that haplotype 1C, found among many
Native Americans (134 of 374 tested, or 36%) and considered to
be a major American founder haplotype, [10] is well-attested among Jewish men. While only
7% of all Jews tested have this haplotype, 31% of the Near Eastern
group of Jews tested positive for it. [11]
Bottlenecks
and Loss of Genetic Information
One
of the phenomena that seriously affect the mtDNA and Y-chromosome
DNA in a given population is the bottleneck, which denotes a period
in the past during which the group’s size was small enough that
only some mtDNA haplotypes survived passage to the next generation
(for which reason the bottleneck is sometimes called the “founder
effect”). For example, a sampling of 16 Kuna Indians of the San
Blas islands on the Atlantic side of Panama disclosed that all
of them were of haplogroup A, with no representation whatsoever
of haplogroups B, C, and D, which are known from tribes to the
north and south. By contrast, two South American tribes, the Yanomama
and the Wapishana (24 and 12 subjects tested, respectively) disclosed
no A at all, though A is the most common haplogroup among natives
of North America. [12] This suggests that carriers of haplogroup B,
C, and D never became part of the Kuna and that carriers of haplogroup
A never became part of the Yanomama, unless they were members
of a group whose genetic material was not passed to modern times.
Geneticists Neil Bradman and Mark Thomas illustrated the problem
when they wrote, “Imagine an island in which over many generations
the population numbers remain constant. Some men have sons, some
do not: those with sons pass on their Y chromosomes while the
Ys of the others are lost to history.” [13]
Disease is sometimes responsible for the bottleneck. In the
case of Native Americans, many died from diseases brought by European
explorers, while others were slain in battle. A study of Precolumbian
skeletal remains noted that, “An alternative hypothesis is that
the apparent reduction in contemporary Amerindian mtDNA diversity
reflects a borttleneck not during initial colonization, but rather
as a consequence of the well-known demographic collapse of Amerindian
populations following European contact ... if the apparent reduction
in contemporary Amerindian mtDNA diversity is instead associated
with the demographic collapse following European contact, then
there would be additional mtDNA lineages in pre-Columbian populations
that are not found in contemporary populations.” [14]
It has been estimated that from one-half to one-third of the
native American population of highland Guatemala may have died
from smallpox even previous to the arrival of the Spanish to that
region. [15] “At least eight serious epidemics swept across
Guatemala between 1519 and 1632, and localized episodes of sickness
occurred even more frequently over the same period of time.” [16] “Both Spanish and Indian sources extant for the
study of disease outbreaks in sixteenth-century Mexico exhibit
awareness of, if not alarm at, the high rate of mortality that
sickness brought about, exceptional even by the standards and
perceptions of the time.” [17]
In Central Mexico between 1521 and 1595, there were at least
eleven major epidemics that devastated native American populations
of the region. [18] Moreover, as one recent study of these epidemics
concludes, “Population decline could not have taken the gradually
increasing course” assumed by earlier demographers, “rather, depopulation
must have set in abruptly, soon after the arrival of smallpox,
to lessen in intensity later on, interrupted always by periodic
outbreaks of other grave sicknesses.” [19]
That the first diseases introduced from the Old World to the
New found ideal conditions for the rapid transmission of sickness
across vast distances is indisputable. Sizable populations existed
that were immunologically defenseless against the quick work of
unknown pathogens. Diseases passed back and forth as long as the
chain of vulnerability was unbroken. After a century or so, during
which time depopulation in many regions on the order of 90 percent
or more had occurred, pandemic activity abated, probably because
both the size and density of Indian populations had been reduced
to a level at which the possibility of the spread of new diseases
was curtailed. [20]
Periods of serious demographic decline were not limited to
the age of Columbus and the Spanish explorers. Archaeological
evidence suggests that precolumbian Mesoamerica also experienced
at least several periods of serious demographic decline, at least
in certain regions. While the exact causes of these decreases
in population are at present the subject of controversy, Mesoamerican
scholars have marshaled evidence for various explanations including
disease, warfare, and drought, or combinations of these. [21] Michael Crawford, a University of Kansas anthropologist,
noted that, “Today’s American Indians are survivors of a violent
collision of the Old and New Worlds that occurred 500 years ago,”
and that “the total Indian population dropped from about 44 million
people to fewer than 10 million,” in the first 200 years of contact
in North and Central America. [22]
The key point here is that whatever their cause, the drastic
decline in precolumbian Mesoamerican populations, in addition
to those caused by postcolumbian diseases, would have resulted
at various times in a genetic bottleneck, with a loss of significant
amounts of genetic information. This would result in the fact
that the remnant of precolumbian populations likely had many ancestors
who may not be well represented in the genes of modern Native
Amerindians. Indeed, some Native American tribes, such as the
Mandans and the Mohicans, have disappeared altogether.
It is interesting that, of the four “Native American” mtDNA
haplogroups, one (B) is has not been found in Siberian populations.
One report declares, “While the absence of haplogroup B from Eastern
Siberia might suggest an additional migration, presumably from
southern coastal Asia or South-Central China, where [it] is more
common, it is also possible that haplogroup B was present in Eastern
Siberia before the New World was colonized but has since become
extinct there.” [23]
Genealogy
vs. Genes
Some critics of the Book of Mormon seem to believe that genetics
and genealogy are identical. While both words derive from a common
Greek source, they are not really the same thing. The pedigree
chart that follows will illustrate. It lists six generations of
a single individual. Think of yourself as the figure at the bottom
of this chart, with all the others representing your ancestors.
click
to enlarge
As for nuclear DNA (nDNA), since each child receives half from
his/her mother and half from his/her father, this DNA has a half-life
in each generation. You have 50% of your mother’s nuclear DNA
and 50% of your father’s, but since the same is true for each
of them and for all of your other ancestors, you have received
an average of only 25% of your nuclear DNA from a grandparent,
12.5% from a great-grandparent, 6.25% from a second great-grandparent,
3.125% from a third great-grandparent, and so on. In this chart,
you will have received an average of 1/64 (1.5625%) from each
of your fourth great-grandparents.
I use the term “average” because it is possible to receive
a higher or lesser percentage from a given ancestor (except parents).
For example, while each of your parents gets 50% of his/her DNA
from each of her parents, it is likely that he/she only passes
to you more of the nDNA of one of those parents than the other.
Over time, it is possible that the DNA of some of your distant
ancestors was lost and did not survive into modern times. Over
long periods of time, you will find that several of your ancestral
lines coalesce or go back to the same individuals, meaning that
you may have received some of your DNA from each of them through
a different set of ancestors.
Expanding the pedigree chart to ten generations, you will have
listed 1,024 of your ancestors. Assuming four generations per
century, 15 generations would take you back a mere 400 years,
at which time you will have a total of 32,768 ancestors who lived
during those four centuries. According to the Human Genome Project,
every human has 32,040 different genes in his/her nDNA. This means
that for those 15 generations, you have more ancestors in your
pedigree chart than you have genes! The actual number of distinct
individuals will be less because of coalescence. The authors of
a recent study on “Genealogy in the Era of Genomics” wrote:
Mitochondrial DNA has provided groundbreaking insights
into the history of humans. However, mtDNA tells only part of
the story: we know that we have, potentially, as many contributors
to our genes as ancestors in our genealogical tree. ‘Mitochondrial
Eve’ and ‘Y-chromosome Adam’ need not be contemporaries or live
in the same region, and they are not necessarily the most important
contributors to our genetic makeup. In fact, if we had one common
ancestor at some particular time, we almost certainly had many
of them. Mitochondrial Eve merely happens to be the one who is
our mother’s mother’s mother’s (repeat this many thousand times)
mother. Mitochondrial analysis cannot tell us who is our mother’s
father’s mother’s father’s (repeat this many thousand times) father.
Some of these undetectable ancestors may have lived a good deal
more recently than Mitochondrial Eve.
It is also worth noting that common ancestors do not
necessarily make equal contributions to our genome. It is true
that our parents each contribute 50 percent of our genetic material,
but our grandparents do not necessarily each contribute 25 percent.
Going farther back, some ancestors may have their genetic contribution
enhanced by genealogical coalescence: More branches leading to
them translates to more opportunities to pass their DNA down to
us.” [26]
In sum, it is a gross oversimplification for Book of Mormon
critics to suggest that genealogy and genetic inheritance are
the same thing. Geneticist Steve Olsen wrote, “Being descended
from someone doesn’t necessarily mean that you have any DNA from
that person.” For example, “The amount of DNA each of us gets
from any one of our 1,024 ancestors ten generations back is minuscule
— and we might not get any DNA from that person, given the way
the chromosomes rearrange themselves every generation.” [27]
HLA
Studies
Another method of tracing the origin of some of one’s ancestors
is to examine the human lymphocyte antigens (HLAs) that make up
the immune system. HLAs are proteins or white blood cells produced
by specific genes passed from parent to child. In recent years,
medical experts have had to pay more attention to these HLAs because
they, like blood types (A, B, AB, O) and other blood characteristics
(Rhesus, Kell, and Duffy), play a role in the rejection of transplanted
organs.
The actual number of human alleles responsible for HLAs is
relatively small. According to a recent study by James L. Guthrie,
some isolated South American tribes possess only a few
types that are common throughout the Americas. But other groups,
especially those near sites of former Mesoamerican and Andean
urban societies, exhibit HLA alleles that are rare in America
but common in certain Afro-Asiatic, southern Asian, and European
populations. These unexpected genes account, on the average, for
6-7% of the [Native] American HLA total, but range as high as
24% [in some groups]. The atypical genes are postulated to have
been acquired by assimilation of foreign populations in various
times after initial colonization of the hemisphere but prior to
the sixteenth-century influx of Europeans and Africans, because
they suggest gene-flow from places that were, according to some
scholars, in ancient contact with the Americas, such as North
Africa and Southeast Asia. [28]
Guthrie notes that “This diversity gives population geneticists
a powerful tool for tracing ancient migrations, and, at present,
HLA distributions are more informative in this regard than are
any other genetic system except DNA.” [29] At the time the article was published in 2001,
there were, worldwide, “29 HLA families for which there are enough
data to construct useful distribution maps,” with “many more types
that are less well mapped at the present time.” [30] “Only twelve type-A and 17 type-B HLAs were sufficiently
well sampled for useful worldwide comparison,” and there were
some geographical regions that were not well represented by the
sampling. [31]
Native American populations “near the urban societies of Mesoamerica
and the Andes have the most” HLA alleles (up to 26), while “some
marginal tribes of South America have the fewest. The degree of
HLA diversity in a population may be a measure of its former size
and cosmopolitan nature.” [32] Four of the type-A HLAs account for 94% of the
American HLA-A total, while six of the type-B HLAs account for
93% of the HLA-B total, and these are to be considered as markers
for Native Americans. Significantly, “some [isolated] South American
tribes apparently have only these alleles, whereas those near
former urban centers tend to have significant percentages of HLAs
that now are most common in the Near East, India, Africa, Northwest
Europe, or Southeast Asia (including Pacific Oceania),” and hence
are due to admixture with outside groups. [33]
While “some anomalies may be explainable as recent admixtures
... the apparently foreign HLA alleles are usually less characteristic
of Spain, Portugal, or West Africa than of places alleged [by
some archaeologists and linguists] to have had earlier contact,
such as Pacific Oceania, North Africa, or Southwest Asia [i.e.,
the Near East].” [34] On the basis of HLA distribution, Guthrie postulates
ties to various parts of the Old World. Here, we shall deal only
with possible ties to the ancient Near East. Of the 18 “non-Indian”
alleles, the 9 that seem to have originated among Afro-Asiatic
peoples (i.e., the Near East and North Africa) account for 47%
of the total found in Native American populations, with 28% from
the 5 southern Asian alleles and 25% from the 4 European. [35]
Guthrie notes that the highest world frequencies of Afro-Asiatic
HLAs are represented by alleles B*21, A*32, and A*30, attested
in Middle Eastern populations of Saudi Arabia, Jordan/Palestine, [36] the Berber and Tuareg of North Africa, and the
Tigre of Ethiopia (where Semitic languages distantly related to
Arabic and Hebrew are still spoken). [37] Significantly, all three of these alleles are
attested in Central America in the range of 6.5-7.5%. Alleles
A*32 and A*30 appear in even higher percentages in Samoa than
in the Near East. [38]
Guthrie notes that “Central Amerind composite sample is unique
in that all of its ‘non-Indian’ HLAs are of the Afro-Asiatic set”
and concludes that “significant Afro-Asiatic contact with western
Mexico and/or the Caribbean region almost certainly occurred,
probably from Arabia or North Africa.” [39] According to Guthrie, of the foreign alleles,
“A*33 seems to trace movement of a Near-Eastern population to
Southeast Asia and South America,” [40] and contributes “70-80% to the second principal
component, with its strongest effect in eastern North America
and Panama.” [41]
He warns that, “Because human distributions have changed with
time, arguments based on the present situation are not convincing
unless combined with other kinds of evidence,” [42] by which he, being a diffusionist, means archaeological
and linguistic findings that suggest to some scholars that there
were Old World/New World contacts in precolumbian times.
