Y Chromosome Genomic Analysis Suggests Human Settlement in South America May Have Occurred Over 18,000 Years Ago

The American continent's human settlement has been the subject of extensive argument and controversy in the academic community for over 100 years.

Central questions, as reported by EurekAlert!, linked to the time of the arrival, not to mention the spatial distribution patterns, are still open and under discussion.

The scenario, mostly accepted by both genomic and archeological research, is the one that suggests a settlement of the American continent with an intermediate chronology from 18,500 to 13,000 calibrated years before present( cal BP) and the entry of humans into South America shortly after.

Furthermore, other controversial hypotheses propose a longer chronology with a South American settlement before 18,000 cal BP.

Human Y Chromosome

Essentially, the human Y chromosome is used as a highly informative mechanism to examine the history of human populations since it has the longest stretch of non-recombinant DNA in the whole humane genome. It is totally transmitted from father to son, with a record of the paternal lineage's history.

Advances in the complete Y chromosome sequencing technique coming from next-generation sequencing or NGS platforms have made it plausible to develop "robust de novo phylogenetic trees" based on a considerable set of mutational data, where the branch lengths are proportionate to the number of SNPs, and thus, to time.

These studies have proven helpful in offering information and new understandings of human male history.

Essentially, Q Haplogroup in the Y chromosome is the only Pan-American haplogroup and is virtually representing all Native American lineages in Mesoamerica and South America.

American and Eurasian Y Chromosome Sequences Compared

In their research published in PLOS One, the researchers generated new whole Y Chromosome sequences from 13 Argentine samples that belong to Q Haplogroup, non-randomly picked to cover the extent of known Y short tandem repeats or STR diversity.

They compared these to more than 80 samples published globally, belonging to Q Haplogroup, which includes 76 American and 13 Eurasian Y chromosome sequences, leading to an integrated dataset of 102 Y chromosome sequences.

Understanding the link between the Eurasian and American Q-M242 lineages turns out to be more complicated when population changes during the YD period are included.

Since there was no decline in population in the Middle East during the YD period, although it rather served as a refuge for human beings of the time, then the Q Haplogroup lineages before 12,900 years ago, like Q-L275, could have been preserved to a greater extent during the YD occurrence in the Middle East area after this scatter and differentiate until reaching the diversity existing at present for Q Haplogroup in Euro-Asia.

Y Chromosome NGS Sequencing

Nevertheless, Q Haplogroup Native American sub-lineages older than 12,900 years ago would have experienced a drastic drop in the YD period, changing the ancient spatial construction of the human populations of the Americas and causing the lineages' extinction, as well as the loss of part of the gene pool.

Moreover, research needs to include ancient Native American sub-lineages before 12,900 cal BP to understand and approximate the origin of Q-M242.

The study, which was also reported by Bioengineer.org, specified that the reconstruction of the first South American settlements still necessitates further research.

Y chromosome NGS sequencing has proven to be an extremely essential tool, and future research with a huge number of diverse individuals who have Native American ancestry from all over the continent, and a large number of sequences that belong to ancient Native American sub-lineages, would enormously add to this field.

Related information about Y Chromosome is shown on Geo Nomad's YouTube video below:

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