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As far as I know, the oesophagus in vertebrates has no digestive or absorptive function. It is simply a conduit from the mouth to more distal parts of the gastrointestinal tract. Why have it at all, then? What evolutionary advantage does it give? Why not have the stomach start right where the mouth/pharynx ends?

Could it be to make space for the heart?

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  • $\begingroup$ Some fish do this, but if you want a neck (and if you live on land you do) you need to space things out. narrower fish use it to give space for the gills. $\endgroup$
    – John
    Apr 21, 2020 at 0:31
  • $\begingroup$ Because of the lungs - they need their own space to expand and contract. $\endgroup$
    – Polypipe Wrangler
    Apr 21, 2020 at 11:49
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    $\begingroup$ That's a cool question! I think (just a thought, hence not an answer) the stomach needs space since it moves to churn food, and there are already have two vital 'moving' organs in the thoracic cavity. Additionally, it would be easier to have a lower position for the stomach to transfer the chyme down to the intestines, rectum, anus and finally eliminate it from a point far away from the mouth- for hygienic purposes. $\endgroup$
    – Bipasha
    May 12, 2020 at 12:15
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    $\begingroup$ @Varsh04802_Lr That's a possibility. But the words 'mouth' and 'hygienic' should not be used in the same sentence. The human oral cavity is home to hundreds of species of bacteria (see ncbi.nlm.nih.gov/pmc/articles/PMC1287824). It's so filthy, some even call it the glorified rectum. $\endgroup$
    – Adhish
    May 12, 2020 at 16:51

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