I am not a historian, but I think it is in the spirit of this subreddit to bring up work done by microbiologists who study ancient DNA. The European Academy of Bozen (EURAC) was a primary player in this research as well as the Bustamante Lab at Stanford. The story of how Otzi’s DNA was sequenced and the topic of ancient DNA more generally would take me too far off topic, so I’m going to focus on what sequencing was able to tell us with references at the end. Consequently, I’m going to use a partially narrative format.

Otzi’s paternal and maternal lineages can be determined separately from each other by studying his Y chromosome (paternal) and his mitochondrial DNA (maternal). Otzi’s Y chromosome lineage is currently found mostly in Sardinia. Now, this was a surprise at the time to both the Austrians and Italians who each wanted to claim Otzi as a national ancestor!

But how did he get from Sardinia into the Alps? It turns out that a deeper analysis of genetic admixture overturns this hypothesis. After the initial Sardinia claim was made, researchers were able to identify ancient DNA sequences in several individuals that suggest there were two major populations: hunter-gatherers and farmers. The hunter-gatherers had arrived in Europe earlier and then were initially pushed into Northern Europe with the arrival of farmers. Later, the two populations mixed. Except, some areas saw little to no mixture and among these was Sardinia.

So when it was reported that Otzi appeared to be a descendant of modern day Sardinians, what was actually found was that Otzi belonged to the farming lineage before it had mixed with hunter-gatherers. He likely lived only a short distance from where his corpse was found.

Unfortunately, Otzi’s matrilineal line appears to be extinct. When coupled with what we know about his Y chromosome, this is compatible with the assumption of a population that had stopped migrating and did not grow demographically, although this point has not been proven. It may instead be that not enough modern mitochondrial DNA sequences have been taken to identify the matrilineal descent.

I am trying to find the studies done of ancient plant DNA found on Otzi’s corpse (think: seeds and pollen) but the Bustamente Lab has broken links on their website and it is through their current and former staff that I know anything of this topic. What I can say is that ancient plant DNA studies fully supported the claim that Otzi was a farmer and gave us several examples of crops he may have grown, as well as herd animals kept.

References:

Müller W, Fricke H, et al. Origin and migration of the alpine iceman. Science 2003; 302: 862-866.

Keller A, et al. New insights into the Tyrolean Iceman’s origin and phenotype as inferred by whole genome sequencing. Nature Communications 2012; 3: 698.

Sikora M, et al. Population genomic analysis of ancient and modern genomes yields new insights into the genetic ancestry of the Tyrolean iceman and the genetic structure of Europe. PLOS Genetics 2014; doi: 10.1371/journal.pgen.1004353.

Carpenter ML, et al. Pulling out the 1%: whole-genome capture for the targeted enrichment of ancient DNA sequencing libraries. Am J Hum Genet 2013; 93(5): 852-64.