The arrival of Anthropocene epoch

We have heard* about radio carbon dating (measuring carbon-14 decay in organic materials), dendrochronology (analyzing tree-ring patterns), stratigraphy (analyzing the layers of soil and artifacts), Thermoluminescence (this method dates materials that were heated in the past by measuring the light emitted from mineral crystals), Archaeomagnetism (this method analyzes the direction and intensity of Earth's magnetic field as recorded in baked earth or clay to establish the last time the material was heated),  Potassium-Argon Dating (this method is used to date rocks and minerals and is often used in conjunction with archaeology, especially when dealing with volcanic or igneous materials), Fission Track Dating (this method is used to date minerals and rocks by measuring the trails left by radioactive decay of Uranium in the past).

But have you ever heard about plastic trash dating?

Expiration dates could tell us more than when something goes bad! Scientists have found that dates on plastic food and beverage packaging can serve as markers of the Anthropocene, a period in Earth's history marked by the widespread impact of human activities on nature. That is what is happening now!

Here is the story:

The Eurasian coot, a round and black waterbird with a white beak, is a common sight in the Netherlands, along the canals of Amsterdam. In the wild, coots usually avoid reusing their nests, as their preferred building materials are typically fast-decaying plant matter.

The urban population, however, have started supplementing their nesting material with something much more long-lasting—plastic trash created by humans. Since plastic never truly disappears, every bit of old nesting material remains as the birds stack new layers of material, one breeding season after another.

In a study published in Ecology, a team of researchers from the Netherlands revealed that plastic waste in bird nests can serve as a time capsule, allowing biologists to determine when the nests were built by examining expiration dates on the plastic food packaging. In one case, the team traced nest materials back to 1991. 

Scientists have previously used expiration dates to track seafloor litter and piece together extreme flood events from the Anthropocene. Building on this idea, the researchers of this study collected abandoned common coot nests from central Amsterdam on September 22, 2021, after the breeding season ended.
Each nest was then deconstructed and its contents were divided into piles of natural (twigs) and artificial (near-complete packaging) materials. Each artificial item was then carefully examined for manufacturing dates, expiration dates, or any other markings that could reveal its age. The recovered packaging ranged from items like milk and avocados to chocolate packets and fast food wrappers dating back to 1996.
The researchers discovered that two of the collected coot nests had very distinct layers of plastic, making them ideal for stratigraphy—study and interpretation of the layers. One of the nests, which the scientists named "The Rokin Nest," contained plastic waste that was over three decades old.
Nestled at the base of the nest was a candy bar wrapper promoting the 1994 FIFA World Cup while the upper more recent layers hosted discarded face masks from the COVID-19 pandemic. This process of layered accumulation of contemporary human waste is also known as technostratigraphy.

Based on the stratigraphy results and tracking of nesting activity via analysis of archived Google Street View images, the researchers arrived at the conclusion that the Rokin Nest must have been home to at least three generations of coots, as their lifespan is somewhere between 5 to 10 years.
Plastic waste has enabled coots to reuse their nests, giving them more time to forage for food and defend their territory, but this luxury comes at a cost. The researchers noted that old nesting material can be host to harmful parasites like red mites and too much plastic in the nest increases the risk of entanglement for the birds, sometimes resulting in death.

 Auke‐Florian Hiemstra et al, Birds documenting the Anthropocene: Stratigraphy of plastic in urban bird nests, Ecology (2025). DOI: 10.1002/ecy.70010

Expiration dates on food packaging used as nesting material reveal the age of the coot's nest. Credit: Ecology (2025). DOI:10.1002/ecy.70010

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* Archaeological finds are dated using both relative and absolute dating methods, with common techniques including stratigraphy (analyzing the layers of soil and artifacts), radiocarbon dating (measuring carbon-14 decay in organic materials), and dendrochronology (analyzing tree-ring patterns).
Here's a more detailed breakdown of these methods:
Relative Dating:
Stratigraphy:
This method examines the layers of earth or strata where artifacts are found, to understand the chronological order of past human activities. The Law of Superposition states that in undisturbed layers, the deeper a layer is, the older it is.
Seriation:
This method involves arranging artifacts in a chronological sequence based on their similarities, helping to establish a relative timeline.
Cross-dating:
This method compares artifacts from different locations with known dates to establish a timeline.
Absolute Dating:
Radiocarbon Dating:
This method measures the decay of radioactive carbon-14 (C-14) in organic materials like wood, bone, and charcoal, to determine the age of the sample.
Dendrochronology:
This method uses the annual growth rings in trees to create a precise timeline and date wooden artifacts and structures.
Thermoluminescence:
This method dates materials that were heated in the past by measuring the light emitted from mineral crystals.
Archaeomagnetism:
This method analyzes the direction and intensity of Earth's magnetic field as recorded in baked earth or clay to establish the last time the material was heated.
Potassium-Argon Dating:
This method is used to date rocks and minerals and is often used in conjunction with archaeology, especially when dealing with volcanic or igneous materials.
Fission Track Dating:
This method is used to date minerals and rocks by measuring the trails left by radioactive decay of Uranium in the past.

https://crowcanyon.org/education/learn-about-archaeology/archaeolog...