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

Phys · · 669 words · By Kyushu University

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.

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

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Propaganda Score
confidence: 100%
Low risk. This article shows minimal use of propaganda techniques.

fact_checkFact-Check Results

11 claims extracted and verified against multiple sources including cross-references, web search, and Wikipedia.

info Single Source 4
check_circle Corroborated 2
help Insufficient Evidence 2
verified Verified By Reference 1
cancel Disputed 1
schedule Pending 1
verified
“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.
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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)
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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
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://vk.com/wall-181052480_73176
cancel
“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.
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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)
travel_explore
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
“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…
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“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
“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
info
“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/
check_circle
“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
“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…
help
“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.
help
“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.
schedule
“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
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.