Objects – teachanyclass.org

Introduction

In the storage rooms of the Smithsonian National Museum of Natural History sit hundreds of long brown plugs of waxy material. Each one came from inside the ear of a whale. The earliest were collected in the 1870s. The most recent are from the 21st century. Until 2013, they were considered curiosities — useful for figuring out how old a whale was when it died, but not much else. Then everything changed. In 2013, two scientists at Baylor University in Texas — Stephen Trumble (a marine biologist) and Sascha Usenko (a chemist) — published a paper in the Proceedings of the National Academy of Sciences. They had analysed a single 25 cm earplug from a male blue whale that had been hit by a ship near Santa Barbara in 2007. They sliced the plug into thin sections — one for each six-month layer — and analysed the chemistry of each layer. What they found was extraordinary. Each layer preserved a chemical biography. Cortisol (the stress hormone) was high during periods when the whale would have been encountering ships or being chased. Testosterone surged at puberty. The whale's exposure to ocean pollutants — mercury, DDT, PCBs, flame retardants — was recorded in the lipid layers, traceable to the specific six-month period when the whale had absorbed them. The earplug was a complete chronological record of the whale's 12-year life. Trumble and Usenko had discovered that whale earwax is a biological archive — like tree rings, ice cores, or coral skeletons, recording environmental information that humans did not put there. Subsequent research has extended the analysis to earplugs going back to whales killed in the 1870s, allowing scientists to track 150 years of ocean change. This lesson asks how a strange substance becomes a window onto our ocean.

The object

Origin: From baleen whales (especially blue, fin, humpback, minke) and sperm whales worldwide. Major scientific collection at the Smithsonian National Museum of Natural History. Many were collected at whaling stations between the 1950s and 1980s.
Period: Whale earwax has accumulated for as long as whales have existed. Scientific use to age whales dates from the 1950s. The discovery that earwax preserves chemical biographies dates from a 2013 paper by Stephen Trumble and Sascha Usenko at Baylor University.
Made of: Layers of cerumen — a mixture of keratin (from skin cells), lipids (fats), and proteins. Light layers reflect feeding periods (more lipid droplets from prey); dark layers reflect migration or breeding periods. Trace hormones and pollutants are preserved in the lipid layers.
Size: A typical blue whale earplug is 25-50 cm long and weighs up to 1 kg. Each pair of light-and-dark layers represents about six months. A 70-year-old whale might have 140 layers — a complete chronological record.
Number of objects: The Smithsonian alone holds over 1,000 earplugs in its collection. Other major museums hold smaller collections. The total across all scientific collections is several thousand, ranging from the 1870s to today.
Where it is now: Major scientific collections at the Smithsonian National Museum of Natural History, the Natural History Museum London, the New Bedford Whaling Museum, and various marine biology institutions. Many earplugs are still being studied for new chemical analyses.

Before you teach this — reflect

Questions for you

Whale earwax sounds like a joke; it is actually serious science. How will you treat the topic with appropriate seriousness without losing the genuine surprise?
Many of the earplugs were collected at whaling stations during periods when whaling killed millions of whales. How will you handle this honestly?
Ocean pollution is a serious ongoing problem. How will you teach this without being preachy?

Common student difficulties — tick any you have noticed

My students may not know that whales accumulate earwax in their ear canals throughout their lives, with light and dark layers like tree rings.
My students may not know that the Smithsonian has over 1,000 whale earplugs in its collection, going back to whales killed in the 1870s.
My students may not know that in 2013 scientists discovered that whale earwax preserves a chronological record of stress hormones, sexual maturity, and ocean pollutants.
My students may not know that whale earplugs have been used to track changes in ocean pollution over 150 years.
My students may not know that whale stress (measured by cortisol in earwax) has risen since whaling restrictions came in, partly because of ship noise and climate change.
My students may not know that 'biological archives' include tree rings, ice cores, coral skeletons, and now whale earwax.

Discovery sequence

1

Baleen whales — the giant filter-feeders including blue, fin, humpback, and minke whales — have ears, but their ear canals are tiny. A blue whale, 30 metres long, has an external ear opening only the size of a pencil tip. Inside each whale's ear canal is earwax. Unlike humans, whales do not shed their earwax. It accumulates in distinct layers. During feeding seasons in polar waters, the whale eats vast quantities of krill — a small shrimp-like crustacean. The lipids from the krill end up in the earwax, producing a pale, fatty layer. During migration to tropical waters and breeding seasons, the whale fasts; the wax laid down during this time is darker. A pair of one light layer plus one dark layer represents about six months — one feeding-and-migration cycle. A mature blue whale might have an earplug 25-50 cm long, with 100 or more layers, weighing up to a kilogram. Each layer is a six-month chapter of the whale's life. Scientists have used these layers to age whales since the 1950s. The technique was developed at whaling stations during the era of intense industrial whaling, when scientists had access to thousands of recently killed whales. For decades, that was as far as whale earwax science went. Layers were counted; the plugs were stored. Why might one specific natural object record such precise time information?

Points to consider (for the teacher)

Because the whale's biology happens to lay down material in regular cycles. The seasonal feeding-migration pattern of baleen whales produces alternating layers because the whale's diet and physiology change between seasons. Many other natural systems do similar things — tree rings record annual growth; coral skeletons record water temperature; ice cores record atmospheric chemistry. The earwax is one of many examples of 'biological archives' — natural objects that record time-keyed information without anyone planning it. Each archive has its own strengths. Tree rings reach back a few thousand years. Ice cores reach back hundreds of thousands of years. Whale earwax records both the individual animal and the surrounding ocean, year by year, going back as far as the oldest whale specimens in collections (the 1870s). Students should see that 'data' is not always something humans collect deliberately. Sometimes data is being recorded all around us, waiting for scientists to learn to read it.

2

In 2013, the discovery that changed everything happened almost by accident. Stephen Trumble was a marine biologist at Baylor University in Texas, studying whale physiology. Sascha Usenko was a chemist at the same university, specialising in environmental chemistry. They were colleagues. In casual conversation, Trumble mentioned the whale earplugs that the Smithsonian held. Usenko's chemistry brain immediately wondered: could the earplugs preserve a chemical record? They decided to test this. The Santa Barbara Channel is a major shipping lane off California. In 2007, a 12-year-old male blue whale had been killed in a ship strike there. Marine biologists had recovered the body and saved various tissue samples, including the earplug. Trumble and Usenko sliced the 25 cm plug into thin sections — one for each six-month layer. They analysed each section using mass spectrometry, a technique that can identify and measure tiny amounts of chemicals. The results, published in PNAS in 2013, were stunning. Cortisol (the stress hormone) was elevated during specific periods. Testosterone surged at puberty (around age 6-7 for blue whales), marking sexual maturation. The lipid layers preserved organic pollutants the whale had absorbed: DDT and its breakdown products, PCBs, mercury, and flame retardants. Each pollutant was traceable to the specific six-month period when it had been absorbed. Most importantly, the earplug recorded this information chronologically. Each layer was a snapshot of the whale's life and the ocean it lived in at that time. Why might one paper change a whole field?

Points to consider (for the teacher)

Because it opened up a new way of asking questions. Before 2013, marine biologists had two main ways to study whale stress and pollution: live blood samples (only show current state) and bulk tissue samples (average over the whole life). Earwax provided a third way: a chronological biography. The 2013 paper was also methodologically inspiring — techniques from environmental chemistry could be applied to biological archives in ways nobody had thought of before. The wider point is that 'discovery' often comes from cross-disciplinary thinking. Trumble alone (a biologist) had the earwax. Usenko alone (a chemist) had the analytical techniques. Together, they had a new science. The Trumble-Usenko collaboration is a textbook example of how breakthroughs happen at the boundaries between fields.

3

The Smithsonian's earwax collection includes whales that died in the 1870s. By analysing both pre-industrial and industrial whales, scientists can read 150 years of ocean change. Mercury levels have risen steadily since the late 19th century, primarily from coal-burning power plants. By the 1950s and 1960s, mercury was clearly higher in baleen whales than in 19th-century specimens. DDT — the pesticide first widely used in the 1940s and banned in many countries from 1972 — appears suddenly in earwax from the 1940s, peaks in the 1960s and 1970s, and declines after the bans. Earwax records this rise and fall extremely precisely. PCBs (industrial chemicals widely used from the 1930s) appear in earwax from then; they were banned in the 1970s and 1980s but persist in the environment. Flame retardants appear suddenly in earwax from the 1970s, when they were first widely used. The stress data is also striking. Cortisol levels in baleen whales rose dramatically during periods of intensive whaling (1900-1986). After the 1986 international moratorium on commercial whaling came in, cortisol fell. Then, since the 1990s, cortisol has risen again. Whales are not being hunted anymore. What is stressing them? The answer turns out to be ship noise and climate change. Cargo ships, military sonar, and oil exploration make whale habitats noisy. Climate change has shifted krill distributions, sometimes leaving whales unable to find enough food. Both stressors show up in cortisol. What does this teach us?

Points to consider (for the teacher)

That ocean pollution and whale stress are not just abstract concepts — they are recorded year by year in the bodies of the whales. Earwax provides ground truth for environmental history. We can see the rise and fall of specific chemicals as policies have changed. The DDT story is a major environmental success: a chemical that once threatened many species was identified, banned, and is slowly disappearing from the environment. The whale stress story is more concerning. Even though we have stopped hunting whales, we are still stressing them through other human activities. 'Helping whales' requires more than just stopping hunting — it requires reducing ship noise, controlling climate change, managing fishing pressure on whale food supplies. Strong answers will see this is a real ongoing question.

4

The whale earwax story has expanded to other biological archives. Seabird feathers preserve traces of mercury and other pollutants. Coral skeletons preserve ocean temperature and chemistry over centuries. Otoliths (small calcium structures in fish ears) record fish life histories similarly to whale earwax. Old tooth enamel preserves dietary records of ancient humans and animals. Museum collections that were once considered curiosities have become valuable scientific resources. Specimens collected by 19th-century naturalists turn out to preserve information that nobody at the time imagined would ever be useful. New analytical techniques keep finding new uses for old collections. This is sometimes called 'specimen rescue' — the realisation that older specimens are valuable for new questions. The Smithsonian, the Natural History Museum London, and many other institutions have begun explicitly preserving specimens for future use, with awareness that the next 50 years will probably bring new analytical techniques nobody can predict. What does this teach us?

Points to consider (for the teacher)

That museums are not just places to display objects — they are libraries of biological information. Each specimen is a multi-dimensional record that could be read in many ways. Some readings are obvious immediately (counting earwax layers to age whales). Some readings only become possible with new technology (chemical analysis for pollution and hormones). Some readings have not been thought of yet. The wider lesson is about the value of preservation. Museum specimens that seemed unimportant when collected can turn out to be irreplaceable. The Smithsonian's 1,000+ whale earplugs were 'just earwax' for decades. They are now one of the most important records of ocean change of the last 150 years. Students should see that 'old specimens' are reserves of potential information for questions we have not asked yet. The earplugs in the Smithsonian basement are still being analysed; the whales they came from died decades ago, but their stories are still being read.

What this object teaches

Whale earwax is the cerumen that accumulates in the ear canals of baleen whales (blue, fin, humpback, minke) and sperm whales throughout their lives. Unlike humans, whales do not shed their earwax. It builds up in distinct light-and-dark layers — light during feeding periods (full of lipids from prey), dark during migration and breeding periods. Each pair of layers represents about six months. A mature blue whale's earwax plug can be 25-50 cm long, weigh up to 1 kg, and contain 100 or more layers — a chronological record of the whale's life. Scientists have used earwax to age whales since the 1950s. In 2013, Stephen Trumble and Sascha Usenko at Baylor University discovered that earwax also preserves a chemical biography. Each layer records the whale's hormones (cortisol, testosterone) and the pollutants the whale was exposed to (mercury, DDT, PCBs, flame retardants). Their PNAS paper, analysing a 12-year-old male blue whale's earplug, opened a new field. Subsequent analysis of earplugs from whales killed since the 1870s has tracked 150 years of ocean change — the rise and fall of DDT after its 1972 ban, the rise of mercury, the appearance of flame retardants from the 1970s, and changing whale stress. Whale stress fell after the 1986 commercial whaling moratorium but has risen again since the 1990s, partly from ship noise and climate change. The Smithsonian holds over 1,000 whale earplugs. Whale earwax is a major example of 'biological archives' — natural objects that record information humans did not put there.

Date	Event	What changed
From the 1870s	Earliest whale earplugs in scientific collections	Beginning of the modern record
From the 1950s	Scientists use earwax layers to age whales	Counting layers becomes a standard technique
1940s onwards	DDT appears in whale earwax	Pesticide use begins; recorded in whale tissues
1972	DDT banned in the United States	Many other countries follow; DDT begins declining in earwax
1986	International moratorium on commercial whaling	Whale stress falls in subsequent earwax
From the 1990s	Whale stress rising again	Ship noise and climate change become major stressors
2013	Trumble and Usenko publish landmark PNAS paper	Earwax revealed as chemical biography of whale life
Today	Earwax used to track ocean pollution and whale stress over 150 years	Major resource for marine conservation science

Key words

Cerumen

The medical term for earwax — a waxy substance produced in the ear canals of mammals, made of keratin, lipids, and proteins. Whales accumulate it; humans shed it.

Example: All baleen whale cerumen is the wet type. The same chemistry that produces human earwax produces whale earplugs.

Baleen whale

A whale that uses comb-like baleen plates instead of teeth to filter small prey from seawater. Includes blue, fin, humpback, minke, sei, and bowhead whales. All baleen whales accumulate earwax plugs.

Example: The blue whale is the largest animal ever to have lived — up to 30 metres long and 200 tonnes. The bowhead whale can live over 200 years; its earplug provides one of the longest biological archives from any single individual.

Earplug (whale)

The plug of accumulated earwax in a whale's ear canal. Light layers reflect feeding seasons; dark layers reflect migration or breeding periods. Each pair of layers represents about six months.

Example: A 70-year-old blue whale might have 140 layers in its earplug. Each layer can be analysed individually for hormones and pollutants, giving a six-month resolution chronological record of the whale's life.

Stephen Trumble and Sascha Usenko

Marine biologist (Trumble) and chemist (Usenko) at Baylor University in Texas. Their 2013 paper in PNAS on a single blue whale earplug founded the field of whale earwax chemistry.

Example: Their 2013 paper analysed a 25 cm earplug from a blue whale killed in a 2007 ship strike near Santa Barbara, California. They sliced the plug into thin sections and analysed each one separately, recovering a complete 12-year chemical biography.

Biological archive

A natural object that records environmental or biological information humans did not put there. Examples include tree rings, ice cores, coral skeletons, fish otoliths, bird feathers, and whale earwax.

Example: The bristlecone pine has the longest tree ring record (4,500+ years). Antarctic ice cores reach back over 800,000 years. Whale earwax provides 150 years of ocean and individual whale records.

Ship strike

A collision between a ship and a whale, often fatal to the whale. Major shipping lanes through whale habitats cause hundreds of ship strikes per year worldwide.

Example: The 2007 blue whale whose earplug founded the field of whale earwax chemistry was killed in a ship strike. Ship strikes are a leading non-natural cause of whale death today; international efforts to reduce them include speed limits in whale areas.

Use this in other subjects

Science / Biology: Discuss how baleen whales feed and migrate. Their seasonal pattern (summer feeding in polar waters, winter breeding in tropical waters) creates the alternating layers in their earwax. Compare with annual cycles in tree rings, coral, and ice cores.
Science / Chemistry: Discuss mass spectrometry — the analytical technique used to identify trace chemicals in earwax samples. Compare with techniques used for tree ring dating and ice core analysis. Each archive needs its own analytical methods.
History: Build a class timeline of ocean pollution: DDT widespread (1940s), peak (1960s-70s), banned (1972 in US). PCBs widespread (1930s), banned (1970s-80s). Flame retardants (1970s onwards). Mercury rising (1870s onwards from industrialisation).
Citizenship: Discuss the 1986 international moratorium on commercial whaling. Whale populations have begun to recover, though slowly. Whale stress has fallen, then risen again from new sources. Discuss what 'protecting' wildlife means in the modern world.
Ethics: Most whale earplugs in scientific collections come from whales killed during industrial whaling. Discuss the ethics of using these specimens for science now. Strong answers will see that the whales were killed for other reasons; the scientific use is a small good that comes from a large historical wrong.
Art: Look at images of whale earwax plugs and the layered structure. The visual pattern is itself striking — a tree-ring-like record of a life. Discuss how scientific images can be aesthetically powerful.

Common misconceptions

Wrong

Whale earwax is just gross.

Right

Whale earwax is one of the most important biological archives science has discovered. It records 150 years of ocean change and the complete life history of individual whales. The Smithsonian holds over 1,000 specimens; major scientific papers have been published since 2013.

Why

'Just gross' undersells real science.

Wrong

We can't know what whales were exposed to in the past.

Right

Whale earwax provides a 150-year record of pollutant exposure, year by year, for individual whales. By comparing pre-industrial and modern whales, we can directly measure how ocean pollution has changed.

Why

'Can't know' is true of many things, but not of this. The earwax archive is real and growing.

Wrong

After whaling stopped, whales were safe.

Right

After the 1986 commercial whaling moratorium, whale stress initially fell. But it has risen again since the 1990s, partly because of ship noise, climate change, and other modern human activities. Whales today face different but still serious threats.

Why

'Safe' is too simple. Conservation requires ongoing attention to changing threats.

Wrong

Whale earwax is unique to this discovery.

Right

Whale earwax is one of many biological archives. Tree rings, ice cores, coral skeletons, and tooth cementum all preserve information humans didn't put there. Each archive has its own strengths.

Why

The discovery is significant because it joins a wider field, not because it stands alone.

Teaching this with care

Treat whale earwax as the genuinely interesting science it is. Pronounce 'cerumen' as 'seh-ROO-men'. 'Trumble' is straightforward. 'Usenko' as 'oo-SEN-ko'. 'Cortisol' as 'KOR-ti-sol'. Avoid the lazy 'oh, isn't this gross' framing — treat the topic with the seriousness it deserves. Be honest about whaling. Most of the earplugs in scientific collections come from whales killed by industrial whaling between 1900 and 1986, when commercial whaling killed an estimated 2.9 million large whales. This was a major environmental and ethical disaster. The scientific use of these earplugs is a small good that has come from a large wrong. Mention this honestly. Be respectful of indigenous whaling traditions. Some Indigenous peoples (Inuit, Makah, Faroese, Japanese coastal communities) have hunted whales for centuries with cultural and subsistence significance. The 1986 moratorium has exceptions for some indigenous whaling. Distinguish between commercial industrial whaling (which decimated populations) and indigenous subsistence whaling (which has different cultural and ethical dimensions). Be honest about ocean pollution. The earwax record shows real ongoing pollution problems. Mercury, flame retardants, and other pollutants are accumulating in marine ecosystems. Mention without dwelling. Be respectful of the science. The earwax research is genuinely innovative and important. Avoid making the lesson about 'isn't this weird'. Be careful with the 'whales are stressed' framing. Whale cortisol is a real biological measure but should be presented carefully. Avoid anthropomorphising too much; describe the biology accurately. Finally, end the lesson on the present. Whale earwax research is ongoing. The Smithsonian's collection is still being analysed. The story continues.

Check what students have understood

Answer each question in one or two sentences. Use what you have learned about whale earwax.

Why does whale earwax form in distinct layers?

Baleen whales follow seasonal feeding and migration patterns — feeding in polar waters in summer and migrating to tropical waters in winter to breed (where they fast). The earwax laid down during feeding seasons is pale and high in lipids from prey; the earwax laid down during migration is darker and lower in lipids. Each pair of light-and-dark layers represents about six months.

Marking note: Award full marks for any answer that mentions both the seasonal pattern and the resulting layered structure.
What did Stephen Trumble and Sascha Usenko discover in 2013?

They discovered that whale earwax preserves a chronological chemical biography of the whale's life. By slicing a 25 cm earplug from a male blue whale into thin sections, they analysed each section's chemistry separately and recovered hormones (cortisol for stress, testosterone for sexual maturity) and pollutants (mercury, DDT, PCBs, flame retardants) for each period of the whale's 12-year life. They published the discovery in PNAS in 2013.

Marking note: Strong answers will mention both the basic discovery and the kinds of information recovered.
How has whale stress changed since the 1986 commercial whaling moratorium?

After the 1986 moratorium, whale stress (measured by cortisol in earwax) initially fell. Since the 1990s, however, cortisol has risen again. The new sources of stress include ship noise, climate change shifting whale food supplies, and other modern human activities. Whales are not being hunted anymore, but they are still being stressed in different ways.

Marking note: Award full marks for any answer that mentions both the initial fall and the more recent rise.
What pollutants does whale earwax record?

Whale earwax records mercury (rising since the 1870s from coal-burning power plants), DDT (rising in the 1940s, peaking in the 1960s-70s, declining since the 1972 ban), PCBs (rising in the 1930s, banned in the 1970s-80s, slowly declining), and flame retardants (rising in the 1970s, with some recently banned). The earwax provides a chronological record of how ocean pollution has changed over 150 years.

Marking note: Strong answers will mention multiple pollutants and the historical pattern of rise and fall.
What is a 'biological archive', and why does it matter?

A biological archive is a natural object that records environmental or biological information humans did not put there. Examples include tree rings, ice cores, coral skeletons, fish otoliths, bird feathers, and whale earwax. They matter because they let us reconstruct environmental change over periods longer than direct measurements have been made.

Marking note: Award full marks for any answer that mentions both the basic concept and at least one example beyond whale earwax.

Discuss together

These questions have no single right answer. Talk in pairs or small groups, then share your ideas with the class.

Most whale earplugs in scientific collections come from whales killed during industrial whaling. How should we feel about using these specimens for science now?

This is a real ethical question. Possible answers: the whales were killed for other reasons; the science is a small good that came from a large wrong; the scientific knowledge gained helps protect living whales today; refusing to use the specimens would not bring back the dead whales but would lose useful knowledge. The deeper point is that ethical questions about historical specimens are common in many fields. The honest position is usually to use the specimens carefully while acknowledging their problematic origins. Strong answers will see this is a real ongoing question.
Whale stress fell after whaling stopped, but has risen again from ship noise and climate change. What does this teach us about protecting wildlife?

This question is about the limits of conservation. Possible answers: stopping the most obvious threat is not enough; modern wildlife conservation requires addressing many factors at once; threats change over time. Protecting whales today requires reducing ship noise, controlling climate change, managing fishing pressure, and many other things. The whaling ban was important but not sufficient. Strong answers will see that conservation is ongoing work, not a one-time achievement.
What other 'biological archives' might exist that we haven't yet learned to read?

This is a creative question. Possible answers: cementum layers in mammal teeth; growth lines in mollusc shells; fingernail growth lines in humans; butterfly wing chemistry; bone growth lines; layers in fish scales. The deeper point is that nature contains many recording devices we have not yet figured out. Strong answers will think creatively about what natural processes could record information we don't yet have ways to extract. End by saying that some students may grow up to be the scientists who decode new archives.

Teaching sequence

THE HOOK (5 min)

Ask: 'What's the strangest object you can imagine being valuable scientific data?' Take guesses. Then say: 'The Smithsonian has 1,000 plugs of whale earwax. They are some of the most important records of ocean change in the last 150 years. We are going to find out about a substance that sounds like a joke and turns out to be serious science.'
INTRODUCE THE OBJECT (10 min)

Describe whale earwax: builds up in layers over a whale's lifetime, light layers from feeding seasons, dark layers from migration. Each pair of layers = 6 months. A blue whale's plug can be 50 cm long. Pause and ask: 'Why might one substance record time so precisely?' Listen to answers.
THE 2013 DISCOVERY (15 min)

Tell the Trumble-Usenko story. The 2007 ship-struck blue whale. The collaboration between a biologist and a chemist. The slice-by-slice analysis. The PNAS paper. The chemicals found: cortisol, testosterone, DDT, PCBs, mercury, flame retardants. Discuss: what does this kind of cross-disciplinary discovery teach us?
150 YEARS OF OCEAN (10 min)

Tell the wider story. Smithsonian collection going back to 1870s. Pollution rising from industrialisation. DDT story (rise, ban, decline). Whale stress falling after 1986 moratorium, rising again with ship noise and climate change. Discuss: ocean pollution is not abstract — it is recorded in whale bodies.
CLOSING (5 min)

Ask: 'What does whale earwax teach us about how to read nature?' End by saying: 'It teaches that nature is full of recordings nobody planned to make. The whale was just being a whale. Its body recorded its life and its ocean. Scientists have learned to read this recording. The 1,000 earplugs in the Smithsonian basement are still being analysed. The story continues.'

Classroom materials

Read the Layers

Instructions: Show students an image of a sliced whale earplug, with light and dark layers visible. Have them count the layers and calculate how old the whale was when it died (each pair = 6 months). Then discuss: what other natural objects have similar 'tree ring' patterns?

Example: In Mr Aoki's class, students counted layers and calculated that one earplug came from a 47-year-old whale. The teacher said: 'You have just done the same calculation that scientists have been doing since the 1950s. The 2013 breakthrough was realising that we could also analyse what was in each layer chemically.'

Track the Pollutant

Instructions: On the board, sketch a timeline from 1870 to today. Mark when DDT was widely used (1940s-60s), banned (1972), and slowly disappearing. Mark mercury rising from coal-burning. Mark flame retardants from 1970s. Discuss: each pollutant has a story, and each one is recorded in whale earwax year by year.

Example: In Mrs Garcia's class, students were surprised that some pollution stories are real success stories (DDT, PCBs declining) while others are still ongoing problems. The teacher said: 'You have just seen the shape of 150 years of environmental policy. The earwax is the record. The policies that matter — bans, regulations — show up clearly in the data.'

Cross-Disciplinary Discovery

Instructions: In small groups, students discuss: what could be discovered if a biologist and a chemist (or other combinations) collaborated on a question they couldn't tackle alone? Each group invents one possible interdisciplinary research project and explains why it would need both fields.

Example: In one class, students proposed projects combining biology and computer science, chemistry and history, and physics and ecology. The teacher said: 'You have just sketched the future of science. Most major discoveries today happen at boundaries between fields. Trumble and Usenko's whale earwax work is one specific example.'

Where to go next

Try a lesson on the seed bank for another biological archive that preserves information about life.
Try a lesson on the obsidian blade for another natural object that reveals information humans didn't know it had.
Try a lesson on the hand axe for another object whose deep history was discovered through new analytical techniques.
Connect this lesson to science class with a longer project on biological archives — tree rings, ice cores, coral, otoliths, and earwax.
Connect this lesson to history class with a longer project on ocean pollution and environmental policy.
Connect this lesson to citizenship class with a longer discussion of whale conservation, whaling history, and ongoing marine threats.

Key takeaways

Whale earwax is the cerumen that builds up in the ear canals of baleen whales and sperm whales throughout their lives. Unlike humans, whales don't shed their earwax — it accumulates in distinct light-and-dark layers like tree rings.
Each pair of light-and-dark layers represents about six months. A blue whale's earplug can be 25-50 cm long, weigh up to 1 kg, and contain 100 or more layers — a chronological record of the whale's life.
In 2013, marine biologist Stephen Trumble and chemist Sascha Usenko at Baylor University discovered that whale earwax preserves a chronological chemical biography. Each layer records hormones (cortisol, testosterone) and pollutants (mercury, DDT, PCBs, flame retardants).
The Smithsonian holds over 1,000 whale earplugs, with the earliest from whales killed in the 1870s. Scientists are using these to track 150 years of ocean change.
Whale stress (measured by cortisol) fell after the 1986 international moratorium on commercial whaling but has risen again since the 1990s, partly because of ship noise, climate change, and other modern human activities.
Whale earwax is part of a wider category of 'biological archives' — natural objects that record information humans did not put there. Other examples include tree rings, ice cores, coral skeletons, and fish otoliths.

Sources

Blue whale earplug reveals lifetime contaminant exposure and hormone profiles — Stephen J. Trumble, Sascha Usenko et al. (2013) [academic]
Whale Earwax — collection page — Smithsonian Ocean / National Museum of Natural History (2023) [institution]
Whale earwax: a hearing aid & time capsule — oceanbites (2016) [news]
Stress hormones in baleen whales over the last 150 years — Trumble et al. (Nature Communications) (2018) [academic]
The Surprising Science of Whale Earwax — American Academy of Audiology (2024) [news]

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Whale Earwax: A Lifetime in a Plug

Questions for you

Common student difficulties — tick any you have noticed