What Are the Nazca Lines, and Why Were They Made?

Background

In the arid Nazca desert of southern Peru, the Nazca culture, which flourished roughly between 500 BCE and 500 CE, created an enormous body of geoglyphs by clearing the desert's surface layer of dark, iron-oxide-coated stones to expose the lighter soil underneath. The result, more than 800 straight lines (some running over 30 miles), around 300 geometric shapes, and roughly 70 large animal and plant figures called biomorphs, some over 1,000 feet across, remained largely unrecorded until Peruvian archaeologist Toribio Mejía Xesspe conducted the first systematic study in 1926. Wider attention followed only in the 1930s, when commercial pilots flying over the region began reporting the shapes visible from the air.

American historian Paul Kosok began investigating the site in 1941 and, after observing a line align with the setting sun on the June solstice, called the desert "the largest astronomy book in the world," launching the theory that would dominate popular understanding of the lines for the next half-century. German mathematician Maria Reiche then spent forty years documenting, defending, and physically protecting the lines from encroaching development, becoming their most visible champion and the person most responsible for their 1994 UNESCO World Heritage designation.

Main Theories

An Astronomical Calendar

Reiche's theory holds that the lines and figures mark the rising and setting points of stars and constellations across the year, functioning as a working calendar for agricultural timing. The theory's appeal lies in Kosok's genuine solstice alignment and in the sheer scale of the undertaking, which seems to demand an equally significant purpose.

Systematic statistical testing of the lines' orientations, conducted by researchers including Gerald Hawkins in the 1960s, found that the great majority do not align with any astronomically significant point closely enough to rule out coincidence, given how many lines exist and how many possible astronomical targets there are to match against. A calendar built from lines pointing in essentially every direction across the desert floor functions poorly as a calendar.

A Water and Fertility Cult

The theory now favoured by most archaeologists, developed principally by Johan Reinhard and further supported by Anthony Aveni's research, holds that the lines and trapezoids were not primarily meant to be seen, but walked. On this reading, the straight lines and geometric shapes functioned as ceremonial pathways connecting settlements to water sources and to the mountains where rain clouds gathered, walked in procession by community groups petitioning for rain and agricultural fertility in one of the driest inhabited regions on the planet.

The theory fits the underlying archaeological pattern better than the calendar idea: many lines radiate from or terminate near known water sources, and excavated offerings, broken pottery and shell fragments consistent with ritual deposits, have been found along several lines rather than distributed randomly across the desert.

The Ancient Astronaut Claim

A minority claim, popularised by Erich von Däniken's 1968 book Chariots of the Gods, holds that the lines' straightness and scale, only fully appreciable from the air, indicate landing strips or signals built for, or by, extraterrestrial visitors. The claim treats the absence of an obvious ground-level function as evidence of an aerial one.

The claim is rejected by mainstream archaeology on the same grounds it is rejected for the Egyptian pyramids and other sites von Däniken's book cites: excavation has documented the ordinary tools, work camps, and centuries-long construction sequence the Nazca culture actually used, and ground-level visibility is not, in fact, required to lay the lines out accurately, which modern reconstruction experiments using only stakes and cord have repeatedly demonstrated.

What the 2024 AI Survey Found

In September 2024, a joint Yamagata University and IBM Research team published a study in the Proceedings of the National Academy of Sciences describing an AI-assisted survey that identified 303 previously unknown geoglyphs in six months, nearly doubling the total known figures from roughly 430 to over 730. The AI model narrowed the search area dramatically, requiring researchers to inspect only about 36 computer-flagged candidate sites on average to confirm one genuine new figure.

The survey's most significant finding was not the raw count but the pattern it revealed: the newly discovered figures split into two distinct categories with two distinct likely functions. Large line-type geoglyphs, mostly depicting wild animals, align with the elaborate linear and trapezoidal pathway networks and appear to have served community-level ritual purposes, consistent with the water-cult theory. Smaller relief-type geoglyphs, mostly depicting humans and domesticated animals, sit directly along walking trails at ground level, positioned like markers meant to be seen by people passing on foot rather than viewed from above. The find reinforces the ritual-pathway explanation rather than reopening the purpose question, while adding a second, more localised function, communication along trails, that earlier surveys had not identified.

Common Misconceptions

The lines are often assumed to be visible only from an aeroplane or a mountain overlook, a claim the ancient-astronaut theory depends on directly. Many figures, particularly the smaller relief-type geoglyphs the 2024 survey catalogued, sit beside ground-level walking trails and were plainly meant to be encountered on foot; the larger figures, meanwhile, can be laid out accurately from the ground using a planned grid of stakes and cord, without needing to see the finished result from above at any point during construction.

It is also commonly assumed that Maria Reiche's astronomical theory has been definitively debunked as false. More precisely, statistical testing found her core evidence, the frequency of astronomically significant alignments, does not exceed what chance would predict given the number of lines and possible targets; a small number of individual alignments, including Kosok's original solstice observation, remain genuine coincidences that Reiche's broader calendar theory could not adequately explain on its own.

Current Consensus

Archaeologists broadly agree that the Nazca Lines served a ceremonial and religious function connected to water scarcity and agricultural fertility, rather than a primarily astronomical or extraterrestrial one, with the largest lines functioning as ritual pathways and at least some smaller figures serving as ground-level markers along everyday trails. What remains genuinely open is the precise ritual content of each procession, since no contemporary written record survives to explain what participants believed they were accomplishing, and how the two geoglyph types the 2024 survey identified relate to each other functionally rather than just spatially.

Why This Mystery Endures

The Nazca Lines endure in popular imagination largely because of how they were rediscovered: an ancient work legible only from a vantage point, powered flight, that did not exist until roughly 1,500 years after the lines were made, is an unusually vivid setup for speculation about who the intended audience actually was. Kosok's "largest astronomy book" phrase and Reiche's decades of solitary desert fieldwork gave the mystery a compelling human story before von Däniken's alien-landing-strip claim gave it a more sensational one in the following decade.

The mystery has also proven durable because new evidence keeps arriving rather than settling into silence: the 2024 AI survey nearly doubled the known figures in six months, a pace of discovery that would have seemed unimaginable to Reiche walking the desert alone with a broom and a ladder. Göbekli Tepe shows a related pattern in an entirely different setting, a monumental ancient site whose function modern archaeology continues to refine well after its initial excavation. Stonehenge offers the closest direct parallel: another large-scale ancient construction that attracted a confident astronomical-alignment theory long before later, more rigorous analysis showed the true picture was more ritual than calendrical. The Nazca Lines are part of this site's archaeological mysteries cluster, within the broader ancient civilisations coverage.