Machu Picchu

AMS dating (Burger et al., Antiquity 2021, DOI:10.15184/aqy.2021.99) on 26 skeletons from 4 cemeteries indicates occupation as early as ~1420 AD, two decades before the conventional reign of Pachacuti (1438); occupation confirmed through 1532.

A genomic study of 34 individuals buried at the site (Salazar et al., Science Advances 2023, DOI:10.1126/sciadv.adg3377) reveals a population of yanacona (royal retainers) with highly heterogeneous ancestries: coast, Andean highlands, Peruvian, Colombian and Ecuadorian Amazonia — confirming a system of imperial redistribution of labor.

Inca architecture uses dry-jointed polygonal masonry with no mortar: the blocks move slightly under seismic waves and then reposition themselves. The technique withstood the 1650 Cusco earthquake, which collapsed the mortared colonial buildings. Microtremor measurements (Tokeshi, Western Sydney University) confirm that the structures meet current Peruvian seismic-resistance standards.

The hydraulic network comprises 749 m of stone channel with a slope of 1.0–4.8%, 16 cascading fountains and a spring flow rate measured between 26 and 125 L/min (Wright & Valencia Zegarra, Journal of Hydraulic Engineering ASCE 1997, DOI:10.1061/(ASCE)0733-9429(1997)123:10(838)). Wright estimates that 60% of the construction effort was underground (foundations, drainage).

The astronomical alignments are documented: the east window of the Temple of the Sun frames the sunrise at the June solstice; the Intihuatana (gnomon stone) casts zero shadow at noon during the austral winter solstice (June 21). A formal probabilistic study (Eubanks, Georgia College) confirmed the intentionality of the main structure's orientation.

Ziółkowski et al. (Radiocarbon 2021, DOI:10.1017/RDC.2020.79) publish 11 new ¹⁴C dates with Bayesian analysis on Llaqta de Machu Picchu, Chachabamba and Choqesuysuy, suggesting an initial phase between 1391 and 1460 AD (95.4% CI) and occupation preceding the main citadel.

The historic sanctuary inscribed as a UNESCO World Heritage site (ref. 274, 1983, criteria i, iii, vii, ix) covers 38,160 ha at over 2,400 m elevation. The citadel comprises about 200 structures spread across agricultural, residential and religious sectors.