January 2020    
  As the new year begins, you may be thinking about your eating habits. Whether you follow a vegan, pescatarian, omnivore, raw, or paleo diet, humans are well adapted to eat a variety of foods, because we developed multifunctional teeth and a jaw that moves in three dimensions. What and how early humans chose to eat further shaped our mouths.  
  Scientists are still chewing over how it all happened, so they continue to trace the jaw's evolutionary journey.  
  Small gulp  
  Microdocodon's slender skeleton suggests that it was an agile and active animal living in trees, with teeth designed for eating insects. (Illustration by April Neander)  
  Mammals are dainty eaters compared to reptiles and sharks, who devour prey whole or in large bites. Scientists now have a Jurassic clue to how modern mammals got their table manners: a "pristine, beautiful fossil" of a shrew-like animal, complete with a tiny movable hyoid bone.  
  Feed news  
The alligator gar, called a living fossil because it has barely changed since the Cretaceous period, vacuums up its prey.
CT images of a 335-million-year-old shark fossil reveal sophisticated jaws capable of the suction feeding found in modern bony fishes.
Arthropod digestion is a whole other animal from vertebrate feeding. A crab chews with three teeth, located in its stomach.
Mammals chew up and down as well as side to side--think of how a cow chews--unlike most modern nonmammals. This ability helped early mammals thrive.
  Vet nurse  
  Baby echidnas--called puggles--can't suckle, so they slurp milk from their mother's skin. This rescued puggle named Beau was nursed at the Taronga Wildlife Hospital outside Sydney, Australia.  
  The ability to suckle, which requires complex mouth and throat anatomy, is a shared characteristic of mammals. But platypuses and echidnas can't nurse.  
  Scientists thought the ability to nurse evolved after the egg-laying mammals split from live-birthing mammals 190 million years ago, but research suggests ancient echidna ancestors could suckle and lost the ability over time.  
  In case you missed it  
Ionic icon: John Goodenough, SM'50, PhD'52, wins a Nobel.
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