In recent
years the development of methods for
sequencing ancient DNA has led to a greater understanding of how many
ancient peoples are related to modern populations, particularly in
Europe. However the method has been little used in the Americas, and
in particular few studies have been carried out on Native American
remains.
In a paper published in
the journal Nature: Scientific Reports on 12 November 2015, a team of
researchers led by Alberto Gómez-Carballa of the Departamento de Anatomía Patolóxica e Ciencias Forenses and Grupo de Investigación en Genética, Vacunas, Infecciones y Pediatría at the Universidade deSantiago de Compostela, describe the results of an analysis of a
seven-year-old male child mummy from Cerro Aconcagua in Argentina.
The child was killed in
an Inca 'capacocha' ritual, in which children of both sexes were
sacrificed similtaneously throughout the Inca Empire on holly days or
in response to events such as volcanic eruptions, droughts,
earthquakes, battles or the deaths of Emperors. The Incas extended
their empire from Peru southward into Chile and Argentina between
1438 and 1533 (when the last Inca Emperor, Atahuallpa, was executed
by the Spanish Conquistador Francisco Pizarro), giving a time of
death for the child constrained to within a century.
The Aconcagua mummy.
The inset shows a picture of a portion of dissected lung from the
mummy. A small piece of 350 mg was used for DNA extraction.
University of Cuyo in Gómez-Carballa et al.
(2015).
Gómez-Carballa et al.
examined the mitochondrial DNA of ttissue taken from the lung of he
mummy in order to assess its ancestry. Because mitochondrial DNA is
found in the mitochondria, organelles outside the cell nucleus, it is
passed directly from mother to child without being sexually
recombined each generation, enabling precise estimations of when
individuals shared common ancestors, at least through the female line
(it is also possible to trace direct ancestry through the male line,
using DNA from the Y chromosome, which is passed directly from father
to son without sexual recombination).
The
mummy was found to belong to the C1b haplogroup (a haplogroup is a
group of individuals shown to share a common acestry through the male
or female line, using either mitochondrial or Y chromosome DNA). This
is one of the most common Native American haplogroups, and is also
known from some very ancient American remains. The common ancestor of
all people with the C1b haplogroup is thought to have lived between
20 400 and 16 200 years ago, either in Beringia (the area of land
connecting Alaska to Siberia, which was exposed during the last ice
age when sea-levels were much lower) or in the earliest settlements
in North America, though the C1b haplogroup appears very early in
both Central and South America, suggesting that the group of people
in which it was found expanded southwards very rapidly.
The
C1b haplogroup is divided into a number of clades (a clade is a group
of organisms defined by haing a common ancestry), but the Inca mummy
cannot be placed within any of these. Instead it is placed in a new
clade C1bi, where i
stands for 'Inca', which appears to have branched from its closest
relatives around 14 300 years ago. The closest previously described
clade to C1bi is
C1b13, though all members of this group are thought to have shared a
common ancestor about 11 800 years ago, so C1bi
cannot comfortably be placed in this group. C1b13 is virtually absent
from both North and Central America, and is most abundant in Chile,
suggesting that the ancestor of this group lived in southern South
America. This suggests that C1bi
also bellongs to a lineage from southern South America, probably
within the southern Andes. While this is the first individual
discovered with this haplotype it cannot be inferred that the
haplogroup is extinct or even especially rare; low sampling of
mitochondrial DNA among living populations in the area means that
potentially the haplotype could be very abundant today.
See
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