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What
is race?
Race is complex, and in general usage, is both a cultural
and biological feature of a person or group of people. Given
the fact that physical differences between populations are
often accompanied by cultural differences, it has been difficult
to separate these two elements. Over the past few decades
there has been a movement in several fields of science to
oversimplify the issue declaring that race is â€omerely
a social construct�. While, indeed this
may often be true, depending on what aspect of variation
between people one is considering, it is also false for many
particular instances of differences between the populations
of the world. One clear example of a biological difference
is skin color. Culture or environment has almost no
effect on the level of pigmentation in a person's skin. Yet
there are dramatic differences across populations. Pigmentation
is, however, only skin deep and really quite simple in light
of the complex environments in which we all live and how
these affect our individual and group quality of life.
It
is clear that the human species is relatively young. As
a species, we most likely originated in east Africa 100,000
years ago, and diverged as groups to settle the globe.
During these migrations, and in the time since, there has
been some degree of independent evolution of the populations
that settled the various continents of the world. The
simplest evidence of this evolution can be seen in the
differences in allele frequencies at genetic markers. Generally,
we see that alleles found in one population are also found
in all populations and the alleles that are the most common
in one are also common in others. These similarities
between populations highlight the recent common origin
of all populations. However, there are examples of
genetic markers which are different between populations
and it is these markers, called Ancestry Informative Markers
(AIMs), which can be used to estimate the Ancestral origins
of a person or population.
What
is BioGeographical Ancestry (BGA)?
BioGeographical Ancestry (BGA) is the term given to the
biological or genetic component of race. BGA is a simple
and objective description of the Ancestral origins of a person,
in terms of the major population groups. (e.g. Native American,
East Asian, Indo-European, sub-Saharan African, etc.) BGA
estimates are able to represent the mixed nature of many
people and populations today. In the US, as in many
other countries across the globe, there has been extensive
mixing among populations that had initially been separate. In
the fields of human genetics and anthropology, this mixing
is referred to as admixture. BGA estimates can also
be understood as individual admixture proportions, which
take the form of a series of percentages that add to 100%. For
example, a person in question may be found to have: 75% Indo-European;
15% African; 10% Native American ancestry, or they may be
found to have 100% Indo-European ancestry.
How
is BioGeographical Ancestry estimated?
The test uses an especially selected panel of Ancestry
Informative Markers (AIMs) that have been characterized in
a large number of well-defined population samples. These
markers are selected on the bases of showing substantial
differences in frequency between population groups and, as
such, can tell us about the origins of a particular person
whose ancestry is unknown. For example, the Duffy Null
allele (FY*0) is very common (approaching fixation or an
allele frequency of 100%) in all sub-Saharan African populations
and is not found outside of Africa. Thus, a person with
this allele is very likely to have some level of African
ancestry. After the analysis of these AIMs, in a sample
of a person's DNA, the likelihood (or probability) that a
person is derived from any of the parental populations and
any of the possible mixes of parental populations is calculated. The
population (or combination of populations) where the likelihood
is the highest is then taken to be the best estimate of the
ancestral proportions of the person. Confidence intervals
on these point estimates of ancestral proportions are also
being calculated.
How
can BGA estimates be used?
Understanding health disparities. Are there genetic contributions
to the higher rates of hypertension and diabetes in African
Americans or the higher rates of dementia in European Americans? If
not, then what are the cultural or environmental differences
that underlie the prevailing differences? Studies of
these and other diseases require independent, objective measures
of BioGeographical Ancestry (BGA).
Estimates
of BGA can help reconnect individuals separated by adoption,
or some other event, with their ancestral populations.
Even
if a person is not particularly motivated to reconnect
with ancestors, he or she can uncover the past of their
family either to verify family legends or to search for
forgotten roots.
In
the near future, we hope to allow customers to compare
their ancestral proportions to others in their family,
town, city, or state who have chosen to participate. Because
it is based on DNA, and unlike the census, this new tool
will provide the most accurate demographics data that is
possible. We will call this our â€opersonal
demographics� tool.
What
is the medical significance of BGA estimates?
The medical significance of BGA estimate is negligible. Although
some diseases are found at different frequencies in populations
across the globe, hardly any are restricted to one group. The
usefulness of BGA estimates, in biomedical research, comes
from epidemiological analyses where many individuals are
analyzed together to make very general statements about differences
in risk. Even though these results can be very significant,
they have almost no meaning regarding the level of risk for
any one person in the population.
How
is BGA analysis different from mtDNA and Y-chromosomal
ancestry analysis?
There are several commercially available tests of mtDNA
and Y-chromosomal markers, which have been promoted as a
means of learning oneâ€Ts ancestral origins. Although
these tests could provide information regarding the provenance
of some of a personâ€Ts ancestors, they are very
limited. For example, one generation ago a person has
two ancestors, one mother and one father; five generations
ago, a person has 32 ancestors; while 10 generations ago,
a person has 1024 ancestors. Ten generations is roughly
250 years and within the time frame of genealogical interest,
especially when we are considering the settlement of North
America, because they only look at two (2) chromosomes. Y-chromosomal
analysis and mtDNA analysis each could only provide information
on a very small proportion of a personâ€Ts ancestors. Our
test relies on sequences throughout your genome, so we can
say more about a greater number of your ancestors.
Can
BGA provide more specific information about ancestry?
The test is specifically designed to provide information
on the proportions on ancestry on the continental level.
In other words, this test allowed us to uncover the levels
of Native American, European, and African ancestry, as three
component groups. The current BGA test is expanded
to provide information on the proportions of ancestry on
the continental level for most continents, Native American,
Indo-European (which includes European, Middle Eastern and
South Asian groups such as Indians), African, but we distinguish
ancestries within Asia and the Pacific Rim by adding East
Asian, (which includes the Pacific Islanders) as an additional
group. Since there will also be interest in defining
the levels of ancestry within continents (such as distinguishing
Japanese from Chinese, or Northern European from Middle Eastern),
we are in the process of developing a new series of Ancestry
Informative Markers that will provide more insight into where
within a particular continent a personsâ€T ancestors
were most likely derived.
How
can I confirm the significance of a low percentage of
admixture, such as 4% Native American or 3% African?
There are two ways for you to confirm the value of this
estimate: You may have access to historical records
or other provenance that leads you to confirm or refute the
admixture. For example, if your records suggest that
you have a grandparent of East Asian heritage and you register
with the test as of 5% East Asian, the two observations combined
make a stronger case for East Asian ancestry than either
on their own.
You
can obtain the admixture proportions for your father and
mother. Letâ€Ts say you register with
4% African and you want to know whether this 4% is in error
or is accurate. You obtain the admixture proportions
from your parents and each is 100% IndoEuropean. Chances
are the 4% was a result of genotyping error. However,
if your mother was 15% African and your father was 100%
IndoEuropean, your non-zero percentage of African is likely
to be an accurate indicator of African ancestry. This
is similar to option A), where you are relying on two different
sources of information to help you hone in on the most
accurate answer possible. Virtually every test we
have performed on family trees has confirmed these types
of low levels. For example if a person registers with about
11% Native American, and his Father registers with about
20%, his mother about 8% and his sister about 16% Native
American. Given the knowledge from his mother, father
and sister, the 11% takes on a new level of significance.
I
think I have American Indian heritage, but my test results
show that I am 100% Indo European.
There are two possibilities, and the first possibility
is one that many people do not like to hear. We donâ€Tt
mean to offend, but it is a possibility that your suspicion
is unfounded. If you are certain that this is not the
case, the second possibility is that one of your distant
ancestors was indeed American Indian but their genetic contribution
to your composition has been diluted over the generations. This
is a function of the genetic law of independent assortment
and probability, and it depends on how admixed and how distant
an ancestor the person is. What your results show is
that, using our pan-genome test, there is no evidence of
Native American ancestry in your DNA. In the future,
it may be possible (with more sensitive and expensive tests)
to detect your very dilute Native American ancestry.
I think I have American
Indian heritage, but my test results show more East Asian
than Native American admixture. Am I wrong or is
the test wrong?
Neither â€" your results are probably reflective
of one way this test will help reshape notions of our common
history. The result is certainly not an indication
that the test is inaccurate. Using our test, most individuals
suspecting minority (<50%) American Indian heritage confirm
with Native American admixture. Likewise, the test
results for each of several hundred individuals of known
minority (<50%) African, East Asian or Hispanic ancestry
have confirmed with the appropriate admixture. However,
about 10% of the individuals who believe they have American
Indian register as having East Asian as well as Native American
ancestry. Even more surprising, some register with
East Asian ancestry but no Native American ancestry at all! This
result has stirred something of a controversy.
If
you are reasonably certain the ancestor was not him/herself
admixed and was recent in your family tree, there are two
other possibilities. Some of the cases we have processed
are probably explained by Aleut heritage and others are
probably explained by admixture that occurred on the North
American continent prior to European colonization.
Aleuts
were the latest to arrive across the Bering straight and
physically, they resemble East Asians more than other Native
American peoples. Our test is enriched for markers
that have changed in frequency as the human species migrated
to colonize the planet, and there are an adequate number
that distinguish East Asian from Native Americans as evidenced
by the fact that we detect only Native American admixture
in Hispanics and most American Indians. However,
what if Aleuts arrived by boat or over ice after the disappearance
of the land bridge? Would not the molecular distance
between Aleuts and East Asians be lower than between Aleuts
and other Native Americans? This is a distinct possibility,
and since a test such as ours has never existed before,
our results may be teaching us something about the anthropology
of the Aleut group.
The remainder of the cases
may reflect significant and recent East Asian admixture
with Native Americans prior to European colonization. Although
highly speculative, this is a very interesting possibility
because several recent publications have propounded the
idea that East Asians were the first to â€odiscoverâ€?
North America based on archaeological data (â€o1421:
The Year China Discovered America by Natalie Danford, William
Morrow & Co; January 7, 2003). Furthermore, Asian
and Native American ancestries are evident in Russians
and other Europeans (Science Magazine â€oGenetic
Structure of Human Populations�, fig. 1 k=6
references that Russians and the Adygei both have more
non-European ancestry, primarily East Asian and Native
American, in the first figure and then more Central Asian
in the second figure). This idea is controversial,
but if this is true, it may explain your result to a certain
extent. Even so, we simply do not know yet the verity
of this, which tribes harbor East Asian admixture, or even
whether there is a tribe-to-tribe difference at all. As
we learn more, weâ€Tll update this FAQ list
I
thought I was purely of Scandinavian origin, but my results
show minor East Asian admixture. How is this result possible?
Many individuals reporting pure Scandinavian ancestry
register with detectible East Asian admixture as well. This
result may obtain through contribution of the Lapps, indigenous
Scandinavians who share physical features, culture and common
history with Northern Asian populations. Because the
tests is the first such test ever developed to query all
of the human DNA, these results represent original interpretations
of the structure inherent to modern day populations and may
have exciting implications for our understanding of our anthropological
history of the Scandinavian region. If your results
show significant East Asian admixture (greater than 5%),
you should rest assured that at the level of DNA you share
some greater affiliation with East Asians. Even though
we cannot go back into time and prove exactly how this affiliation
came to be, the history of the Scandinavian region gives
us an important clue. One excellent example of a genetic
study showing that a particular Scandinavian population has
East Asian ancestry, was carried out by Rick Kittles and
collaborators on a several sample of Finish from different
regions of Finland (Kittles et al. 2000).
Kittles
RA, Perola M, Peltonen L, Bergen AW, Aragon RA, Virkkunen
M, Linnoila M, Goldman D, Long JC. (1998) Dual origins
of Finns revealed by Y chromosome haplotype variation.
Am J Hum Genet 62:1171-1179.
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