Genome sequencing analyses of “alien” Nazca mummies do not support an extraterrestrial origin

42.89% of reads in sample 2 are confidently assigned to Phaseolus vulgaris, the common bean. This is most easily explained by sample contamination or construction of the putative bone fragment from a bean derivative.

SRA taxonomy analysis confidently assigns 97.38% of the reads in sample 3 to known taxonomic categories. Only 30.22% of reads can be confidently assigned to Homo sapiens, which can initially seem like an indication of some DNA of non-human origin. However, let’s compare this to an SRA taxonomy analysis of a known high-quality human sample.

Here, we see that only 93.15% of reads can be confidently identified – this is actually lower than the percentage of identified reads in sample 3. And only 12.04% of reads are confidently assigned to Homo sapiens – much lower than the 30.22% which can be assigned in sample 3. In this context, sample 3 is almost definitively human DNA. The Abraxas report, discussed earlier, also identifies sample 3 as containing human DNA, and further specifically as a human male.

63.72% of reads in sample 4 are unidentified. This is most easily interpreted as a quality control issue of some kind – potentially caused by sample contamination, or very low-quality data.

The Abraxas report discusses the bioinformatics work that was done to match sample 4 reads to known genomes. Of note, 304,785,398 overlapped reads – a further processing step which the reads uploaded to SRA have not undergone – did not match to any of the tested genomes. However, after removing duplicate reads, this number was reduced by a factor of 10 to 30,823,217.

Continuing this analysis, they assembled the unique unknown reads for sample 4 into contigs. 65.69% of the unmapped reads were successfully assembled and re-matched to known organisms in the NCBI nt database. 97% of the assembled contigs were successfully matched to sequences in the nt database.

To summarize, the reads in sample 4 which could not be matched to tested species are on average highly duplicated reads. When duplicates were removed and the remaining unknown reads assembled into contigs, it resulted in the ability to match 64% of these remaining unknown reads to a database of known organism sequences.

The Abraxas report concludes with an acknowledgment that the NCBI nt database does not contain all sequences for all known organisms, and it is therefore certainly possible that the unidentified DNA reads are from already known (and therefore terrestrial) organisms which are not in the database.

The SRA taxonomy analysis figures still seem evocative, though – 64% unidentified? However, we can see that this is not unusual even for unambiguous ancient human DNA.

SRR17043540 is from a study into ancient Maltese genomes, and we can see that SRA taxonomy analysis gives 57% unidentified reads for this sample.

ERR4863252 is a sample from a single ancient human individual from the location corresponding to present-day France. Although the majority of reads in this sample are identified, 31.27% of reads are still unidentified by the SRA taxonomy analysis. And only 11.04% are confidently assigned as human.