Why emus can't fly: A 'time switch' in bird embryos holds the answer

Phys · May 14, 2026 · 669 words · By Kyushu University

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What to know about Why emus can't fly: A 'time switch' in bird embryos holds the answer

Researchers from Kyushu University have identified a molecular 'time switch' involving the TGF-β signaling pathway that determines whether a bird develops a keel on its breastbone. By comparing chicken and emu embryos, the study demonstrates how a small shift in developmental timing leads to the presence or absence of flight-supporting skeletal structures.

Propaganda risk 0%

Claims checked 11

Techniques found 0

Topics 0

Coverage spectrum

Coverage gap: Low Left coverage

Left0%

Center75%

Right25%

4 sources compared across this story cluster. This is an eFinder estimate from indexed source coverage, not an editorial rating.

What happened

Why emus can't fly: A 'time switch' in bird embryos holds the answer Lisa Lock Scientific Editor Robert Egan Associate Editor Why can eagles soar through the skies while emus are bound to the earth?

Why it matters

One secret lies in a skeletal structure called the keel, a blade-like ridge on the breastbone that anchors the flight muscles needed for powered flight.

Common ground

Flying birds have a prominent one, whereas in flightless birds, the keel never fully forms.

Perspective signals

No major persuasion pattern has been attached yet, so the source, headline, and evidence should carry most of the weight for readers.

Follow-up questions

What concrete event or decision sits underneath the headline: Why emus can't fly: A 'time switch' in bird embryos holds the answer?
What evidence would most clearly confirm or weaken the claim that Seung June Kwon et al, Heterochronic activation of TGF-β signaling drives the diversity of the avian sterna, Nature Communications (2026). DOI: 10.1038/s41467-026-72602-6?
What should readers watch for in the next update to know whether the story is changing?

open_in_new Read the original article: https://phys.org/news/2026-05-emus-fly-bird-embryos.html

analyticsAnalysis

Propaganda Score

confidence: 100%

Low risk. This article shows minimal use of propaganda techniques.

fact_checkClaims Checked

eFinder analyzed this article and checked 11 claims against available evidence, cross-references, web search, and Wikipedia. Here is what the fact-checking layer found.

info Single Source 4

check_circle Corroborated 2

help Insufficient Evidence 2

schedule Pending 1

verified Verified By Reference 1

cancel Disputed 1

schedule

Claim 1: “Seung June Kwon et al, Heterochronic activation of TGF-β signaling drives the diversity of the avian sterna, Nature Communications (2026). DOI: 10.1038/s41467-026-72602-6”

PENDING

This claim was extracted as a checkable statement from the article. eFinder labels it pending based on the available evidence and source context shown below.

verified

Claim 2: “One secret lies in a skeletal structure called the keel, a blade-like ridge on the breastbone that anchors the flight muscles needed for powered flight.”

VERIFIED BY REFERENCE

Wikipedia explicitly defines the keel (carina) as an extension of the sternum that provides an anchor for flight muscles.

travel_explore

web search NEUTRAL — In bird anatomy, the keel or carina (pl.: carinae) is an extension of the sternum (breastbone) which runs axially along the midline of the sternum and extends outward, perpendicular to the plane of th…
https://en.wikipedia.org/wiki/Keel_(bird_anatomy)

travel_explore

web search NEUTRAL — One secret lies in a skeletal structure called the keel, a blade-like ridge on the breastbone that anchors the flight muscles needed for powered flight.
https://phys.org/news/2026-05-emus-fly-bird-embryos.html

travel_explore

info

Claim 3: “In both species, TGF-β remains active until stage 34. In emus, it shuts off there, but in chickens, it continues for about two more developmental stages, through stage 36”

SINGLE SOURCE

The specific timing of TGF-β activity (stage 34 vs stage 36) is only reported in one source. Other sources discuss TGF-β in the context of osteoarthritis or osteoporosis.

travel_explore

web search NEUTRAL — In both species, TGF-β remains active until stage 34. In emus, it shuts off there, but in chickens, it continues for about two more developmental stages, through stage 36, giving the cells an extended…
https://phys.org/news/2026-05-emus-fly-bird-embryos.html

travel_explore

web search NEUTRAL — Objective: Transforming growth factor β (TGFβ) signaling plays a complex tissue-specific and nonlinear role in osteoarthritis (OA). This study was conducted to determine the osteocytic contributions o…
https://pubmed.ncbi.nlm.nih.gov/33022131/

travel_explore

web search NEUTRAL — A recent mouse model based study suggests that blocking TGF-β may improve osteoporosis treatment by helping quiescent osteoblasts in inactive bone surfaces return to an active state.
https://www.pharmatutor.org/pharma-news/2026/blocking-tgf-bi…

check_circle

Claim 4: “Emus, large flightless birds from Australia, are ideal for developmental studies thanks to their well-mapped embryonic stages.”

CORROBORATED

Wikipedia and BirdLife Australia confirm emus are large flightless birds from Australia; the specific utility for developmental studies is reported in the article source.

travel_explore

web search NEUTRAL — Large flightless bird endemic to Australia.Emus breed well in captivity, and are kept in large open pens to avoid the leg and digestive problems that arise from inactivity. They are typically fed on g…
https://en.wikipedia.org/wiki/Emu

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web search NEUTRAL — Emus, large flightless birds from Australia, are ideal for developmental studies thanks to their well-mapped embryonic stages. Despite different adult forms, researchers found that the early developme…
https://phys.org/news/2026-05-emus-fly-bird-embryos.html

travel_explore

web search NEUTRAL — The Emu is one of Australia's most easily recognised birds. With its shaggy grey-brown feathers it is flightless and stands up to 1.9 metres tall.
https://birdlife.org.au/bird-profiles/emu/

info

Claim 5: “In both species, sternal progenitor cells—the immature cells that would eventually form the breastbone—formed on the left and right sides of the embryo and later merged at the center at roughly the same developmental stage.”

SINGLE SOURCE

The provided web search results for this claim are completely irrelevant, discussing sunrise and sunset times in India.

travel_explore

web search NEUTRAL — Sunrise, sunset and moon phases in over 597 locations all across India today.
https://www.timeanddate.com/astronomy/india

travel_explore

web search NEUTRAL — Sunrise and sunset in India as well as day length, twilight and solar noon for every day of the year.
https://sunrise-sunset.org/india

travel_explore

web search NEUTRAL — This table lists today's rise and set times of the Sun from a list of cities of India. Click on each city to visualize full details, or choose different locations from the lists below. Use the followi…
https://theskylive.com/sunrise-sunset-times?cc=IN

check_circle

Claim 6: “keel formation is controlled by a molecular "time switch" called Transforming Growth Factor beta (TGF-β), a signaling pathway that regulates cell growth and division.”

CORROBORATED

One source links TGF-β specifically to keel formation, and another authoritative source confirms that the TGF-β pathway generally regulates cell growth, differentiation, and morphogenesis.

travel_explore

web search NEUTRAL — Gene expression analysis revealed that keel formation is controlled by a molecular "time switch" called Transforming Growth Factor beta (TGF-β), a signaling pathway that regulates cell growth and divi…
https://phys.org/news/2026-05-emus-fly-bird-embryos.html

travel_explore

web search NEUTRAL — Tor Directly Controls the Atg1 Kinase Complex To Regulate Autophagy.
https://www.tandfonline.com/journals/tmcb20

travel_explore

web search NEUTRAL — Transforming Growth Factor-Beta (TGF-β) pathway: Regulates epithelial cell growth, differentiation, and morphogenesis. TGF-β signaling controls Epithelial-Mesenchymal Transitions (EMT) during developm…
https://www.longdom.org/open-access/epithelial-cell-signalin…

info

Claim 7: “In a paper published on April 29, 2026, in Nature Communications, researchers from Kyushu University identified the molecular mechanism behind keel formation.”

SINGLE SOURCE

The specific detail about a paper published on April 29, 2026, by Kyushu University is only found in one specific web result. Other results for Nature Communications are general journal descriptions.

travel_explore

web search NEUTRAL — In a paper published on April 29, 2026, in Nature Communications, researchers from Kyushu University identified the molecular mechanism behind keel formation.
https://phys.org/news/2026-05-emus-fly-bird-embryos.html

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web search NEUTRAL — Publish in Nature Communications: multidisciplinary, open access journal, with 14.7 Impact Factor, 8 days to first decision and 114M annual downloads.Calls for Papers. Editorial Values Statement. Jour…
https://www.nature.com/ncomms/?error=cookies_not_supported&c…

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web search NEUTRAL — The details of nature communications in 2026 like Impact Factor, Indexing, Ranking, acceptance rate, publication fee, publication time.
https://journalsearches.com/journal.php?title=nature+communi…

help

Claim 8: “Pectus excavatum, a common congenital chest deformity known as sunken chest, may arise from overactive proliferation of the same sternal progenitor cells”

INSUFFICIENT EVIDENCE

No evidence was provided in the search results regarding the cause of Pectus excavatum in relation to sternal progenitor cells.

cancel

Claim 9: “Flying birds have a prominent [keel], whereas in flightless birds, the keel never fully forms.”

DISPUTED

While some sources state flightless birds lack a keel, Wikipedia provides a specific counter-example: penguins are flightless but possess a keel for underwater movement.

travel_explore

web search NEUTRAL — Some flightless birds have a keel, such as the penguin; this is because penguins still require strong wing muscles to power underwater movement.[3].Skeleton of an African penguin, possessing a keel, o…
https://en.wikipedia.org/wiki/Keel_(bird_anatomy)

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web search NEUTRAL — These flightless birds, called ratites, are clearly different from other avian species. (Read "Big Bird" in National Geographic magazine.)Tinamous fly, albeit reluctantly. And they possess keeled ster…
https://www.nationalgeographic.com/culture/article/140513-fl…

travel_explore

web search NEUTRAL — Flying birds possess a prominent keel bone, a ridge that extends outward from the sternum.Flightless birds, on the other hand, often have denser bones and larger bodies. This increased weight makes it…
https://enviroliteracy.org/why-cant-flightless-birds-fly/

info

Claim 10: “The paths diverge at stage 34... In chickens, progenitor cells continue to proliferate and form the keel. In emus, they soon mature into cartilage and stop growing.”

SINGLE SOURCE

The specific developmental stage 34 distinction between chickens and emus is only mentioned in one source. Other results discuss different types of progenitor cells (Müllerian or endothelial).

travel_explore

web search NEUTRAL — In chickens, progenitor cells continue to proliferate and form the keel. In emus, they soon mature into cartilage and stop growing.Turning skin cells into limb cells sets the stage for regenerative th…
https://phys.org/news/2026-05-emus-fly-bird-embryos.html

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web search NEUTRAL — These cells invaginate and proliferate forming the Müllerian ducts. Subsequently, pEMT would be reversed to generate differentiated epithelial cells lining the fully formed Müllerian lumen. The anteri…
https://www.frontiersin.org/journals/cell-and-developmental-…

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web search NEUTRAL — Methods: The number of endothelial progenitor cells positive for CD34 and kinase insert domain receptor (KDR) was determined with the use of flow cytometry in 519 patients with coronary artery disease…
https://pubmed.ncbi.nlm.nih.gov/16148285/

help

Claim 11: “Chickens and emus shared a common ancestor around 100 million years ago”

INSUFFICIENT EVIDENCE

No evidence was provided in the search results to verify the common ancestor timeline for chickens and emus.

info Disclaimer: This analysis is generated by AI and should be used as a starting point for critical thinking, not as definitive truth. Claims are verified against publicly available sources. Always consult the original article and additional sources for complete context.