Navigation path

Themes
Agriculture & food
Energy
Environment
ERA-NET
Health & life sciences
Human resources & mobility
Industrial research
Information society
Innovation
International cooperation
Nanotechnology
Pure sciences
  Astronomy
  Biology
  Chemistry
  Mathematics
  Physics
  Other
Research infrastructures
Research policy
Science & business
Science in society
Security
SMEs
Social sciences and humanities
Space
Special Collections
Transport

Countries
Countries
  Argentina
  Australia
  Austria
  Belarus
  Belgium
  Brazil
  Bulgaria
  Cameroon
  Canada
  China
  Colombia
  Croatia
  Cyprus
  Czech Republic
  Denmark
  Egypt
  Estonia
  Finland
  France
  Georgia
  Germany
  Ghana
  Greece
  Hungary
  Iceland
  India
  Ireland
  Israel
  Italy
  Japan
  Kazakhstan
  Kenya
  Korea
  Latvia
  Lithuania
  Luxembourg
  Malta
  Mexico
  Netherlands
  Nigeria
  Norway
  Peru
  Poland
  Portugal
  Romania
  Russia
  Senegal
  Serbia
  Slovakia
  Slovenia
  South Africa
  Spain
  Swaziland
  Sweden
  Switzerland
  Taiwan
  Tunisia
  Turkey
  Ukraine
  United Kingdom
  United States


This page was published on 15/11/2004
Published: 15/11/2004

   Headlines

Last Update: 15-11-2004  
Related category(ies):
Pure sciences

 

Add to PDF "basket"

Sino-Swedish research smells out the truth about the human nose

Our very early ancestors could use their nose to smell but palaeontologists have shown  that they could not breathe through it. The big question until recently was, how did our noses evolve? A pair of researchers from Sweden and China found a fossil that probes the history of the human proboscis.

Complex evolutionary steps gave us human tetrapods the ability to smell and breathe with our noses © PhotoDisc
Complex evolutionary steps gave us human tetrapods the ability to smell and breathe with our noses
© PhotoDisc
It may seem hard to believe but humans – as land-based vertebrates, or ‘tetrapods' which include mammals, birds, reptiles, and amphibians – originally descend from fish. Perhaps easier to believe, is the fact that, unlike us, fish cannot breathe through their nose. Something happened during our evolution to turn our noses from smelling to breathing apparatus.

Min Zhu of the Chinese Academy of Sciences' palaeontology institute and Per Ahlberg of Uppsala University's Evolutionary Biology Centre (SE) uncovered a fossilised piece of the palaeontological puzzle which clarifies, once and for all, how our inner nostril came into being.  Their findings are being reported in Nature (Vol. 432, p.94-97) under the title ‘The origin of the internal nostril of tetrapods'.

Fish have two nostrils on the side of their heads – one in the front and one in back – that form the openings to a little sac containing the olfactory organs. Water flows in through the front nostril and out through the back, but there is no connection to the throat – hence fish can smell but not breathe with their noses. We tetrapods, on the other hand, have an inner nostril or ‘choana' that opens on the palate or in the throat.

This is what makes it possible for us to breathe through our nose. But how did this inner nostril evolve? One thing all scientists agree on is that the front nostril in fish corresponds to our single outer nostril: the question the Sino-Swedish duo tackled was, whether the back nostril was transformed into our choana by ‘migrating' to the palate, or whether the choana is a new opening that arose with tetrapods.

This is a difficult part of evolution to understand, contend the scientists. They say it is easy for us to imagine how evolution deals with small steps, like changing colour or size, but how does a nostril move from the face to the palate? Some experts claim it is impossible for an outer nostril to migrate gradually to the palate because a ‘cord' of nerves and blood vessels runs just inside the row of teeth that the nostril would have to sever during its migration. As the cord is in evidence both in fish and tetrapods, it seems that nothing has happened to it during our evolution.

Insight for developmental biology
To solve this mystery, science turns to the study of fossils, but palaeontologists have failed to find the vital clue. Among the discoveries of fossilised ‘lobe-finned' fish – the closest relatives of tetrapods – it has been noted that some have two outer nostrils but no choanae, just like modern fish. Other lobe-fins, even closer to tetrapods, show a single outer nostril per side and a fully developed choana – a change emerging just before our ancestors crawled onto land. But these still tell us nothing about how the choanae came to be formed.

Now, with the discovery in China of well-preserved coelacanth fossils of a type called Kenichthys campbelli, which are roughly 395 million years old, the two scientists can fill the gap in our ancestral tree between coelacanths with no choana and those that have an inner nostril. Kenichthys has a back nostril that is located on the lip, separating the upper jawbones of the maxilla and premaxilla. This is a halfway point in the nostril migration from the face to the palate, say the duo, a transition that many regarded as an “anatomical impossibility”.

“At this stage, we still don't know how evolution managed to re-forge the contact between the maxilla and the premaxilla and re-establish the cord after the nostril had migrated past,“ Zhu and Ahlberg admit. They hope that future developmental biological research will be able to identify the molecular mechanisms governing the formation of this section of the head. One thing is already apparent: there is a connection between the migration of the nostril in our ancestors and the problem in humans known as cleft palate.

In a human embryo, the upper jaw develops from two separate outgrowths that fuse together beneath the nose, creating a bony bridge that separates the nose from the palate and internal nostril. If this fails to happen, the result is a cleft palate. “It seems that this pattern of development contains a ‘memory' of how our internal nostril migrated onto the palate through a gap in the upper jaw”, says Ahlberg.

AlphaGalileo

Convert article(s) to PDF

No article selected


loading


Search articles

Notes:
To restrict search results to articles in the Information Centre, i.e. this site, use this search box rather than the one at the top of the page.

After searching, you can expand the results to include the whole Research and Innovation web site, or another section of it, or all Europa, afterwards without searching again.

Please note that new content may take a few days to be indexed by the search engine and therefore to appear in the results.

Print Version
Share this article
See also

The origin of the internal nostril of tetrapods (Nature.com)

Cleft palate  (Medline Plus)

Early evolution of tetrapods (Natural History Museum, London)

Tetrapod fossil found – first ever in Asia (National Geographic, 18 December 2002)

Evolutionary Biology Centre (SE)

Chinese Academy of Sciences


Contacts
Research Contacts page
  Top   Research Information Center