The matrilineal genographic family tree is mapped out through markers in the
mitochondrial DNA (mtDNA). Unlike most DNA, mtDNA is inherited from one parent
only – the mother. This means that everyone’s mtDNA has exactly the same
sequence of 16,569 nucleotides as their mother and, consequently, to their
mother’s mother and so on. However, on the very rare occasions where a
mutation occurs, a child’s mtDNA will be different to their mother’s at one
nucleotide, e.g. a G in the sequence might become an A. If that child is a female,
she will then pass this mutation on to her children and they, if they are
female, will pass it on to their children, and so on. Any of her descendants
along a continuously female line of descent will carry the same mutation. Hence,
it can be determined from the presence of that particular mutation in anyone’s mtDNA sequence that they share
that same female individual in whom the mutation first occurred as a common
ancestor along their maternal line of descent.
Each time a mutation occurs, a new branch or subbranch
(haplogroup or subclade) is formed in the matrilinear genographic family tree,
with all bearers of the mutation belonging to the same branch. By tracking the
geographic locations of these haplogroups, particularly among indigenous
populations, the shared ancestry of different population groups can be
determined and the long-term patterns of human migration estimated.
|Kai's father's matrilinear genographic
family tree, as determined by his mtDNA markers, is that of
Haplogroup T* means that the
mtDNA bears the markers 16126C and 16294T but not any of the downstream
markers that define T's subgroups T1 to T5. Haplogroup T* is found through
most of Europe and the Middle East with the highest frequency in the Ural
Mountains and Baltic region. About 10% of the population of Europe belongs
Eve", a woman who lived in Africa approximately 150,000 years ago, is
a common ancestor of all living humans. All existing mtDNA diversity began with
Eve and it remains greatest, and consequently oldest, in Africa.
Haplogroup L3 is an
early offshoot from Eve's mitochondrial genetic sequence. L3 appears only in
Around 80,000 years
ago two mutations gave rise to two offshoots from L3 - the M and N haplogroups from which
all subsequent Eurasian lineages are descended.
About 50,000 years
ago a period of warmer temperatures and moist climate made significant parts of
the Sahara region habitable. This climatic shift likely spurred hunter-gatherer
migrations into the Sahara and thence out of Africa into the Middle East. When
the climate became dry again, the "Saharan Gateway" closed and
isolated them from Africa. Instead they spread around the rest of the world.
In the Middle East, haplogroup N, from which all
European lineages are derived, branched into further subgroups including
haplogroup R. Further branching led to the creation of haplogroups J and T which
appear to have closely related migratory patterns.
About 10,000 years ago, following the last ice
age, J and T migrated into Europe. The strongest migration appears to be fairly
directly northward through eastern Europe to the Baltic but there appears
to have been significant migrations towards western Europe also.
Most of the population of Europe
belong to haplogroups
(including the most common mtDNA haplogroup in Europe, haplogroup H) which
arrived in Europe much earlier, about 30,000 year ago.
The spread of haplogroup T appears to have occurred around
the time of the Neolithic revolution in Europe, so their migration may have been
responsible for spreading the use of farming from the Middle East to the
gatherers who already inhabited Europe.
|Kai's earliest known ancestors
along this lineage come from England. Since haplogroup T is spread through
most of Europe, though without forming a majority in any significant
population, they may have arrived there in an early migration at a time
not much later than the original repopulation of the British Isles after
the last ice age or in any of the waves of migration/invasion from
Continental Europe since then. Since T is also fairly common in the Middle
East it is also possible that they could have originated from there more
recently than the initial migration to Europe 10,000 years ago, possibly
as part of the Jewish diaspora which it thought to have spread mostly
during the period of the Roman Empire.
Geographic's Genographic Project
Above: is a phylogenetic tree of some of the main mtDNA haplogroups with the
numbers that represent their characteristic mutation marked on the
branches. (Lluis Quintana-Murci et.al., 'Where East Meets West: The
Complex mtDNA Landscape of the Southwest and Central Asian Corridor,
American Journal of Human Genetics, issue 74, 2004.)
Below: is a map of the major human migrations out of Africa
colour-coded by time period. (L. David Roper, <http://www.roperld.com/HomoSapienEvents.htm>)