Useless information #36 - How many nostrils do you have? Two? Think again.

The right answer is four.

Humans have two visible nostrils and two internal nostrils called "choanae". These are not primitive useless structures. In fact we need all four to breathe through our noses.

We are not alone. Many mammals and reptiles have four nostrils. Early fish have all four nostrils on the outside.

The fish fossil Kenichthys campbelli has two nostrils in between the front teeth. It seems to illustrate the passage from the outside to the inside.

See you tomorrow for more "Useless information"
RMach

sources:
http://quiteinteresting-qi.wikia.com/wiki/How_many_nostrils_have_you_got%3F
http://knowledgenuts.com/2013/12/01/humans-have-four-nostrils/
http://healthlifemedia.com/healthy/pt/anatomy-of-the-nose/
http://www.nature.com/nature/journal/v432/n7013/fig_tab/nature02843_F2.html