Early Fish Had Lungs

Science Illustrated - - HUMANS -

Our abil­ity to breathe above the wa­ter orig­i­nated long be­fore we be­gan to live on dry land. The ear­li­est boney fish, which were the an­ces­tors of any­thing from cod to hu­mans, had al­ready de­vel­oped prim­i­tive lungs. One of them was the 33- cm-long Guiyu, dis­cover in 2009. Guiyu is the old­est known bony fish, and un­like the ear­li­est ver­te­brates, it had a spine con­sist­ing of ro­bust bones in­stead of car­ti­lage. More­over, the skull had been fur­nished with an im­por­tant ad­di­tion: a lower jaw, al­low­ing the fish more pos­si­bil­i­ties of con­sum­ing food.

The Guiyu fos­sil also demon­strates that the foun­da­tion stones of our arms and legs were be­ing laid. Whereas other fish moved their fins by means of mus­cles close to the spine, Guiyu's mus­cles were prob­a­bly lo­cated in its fins. This new evo­lu­tion­ary trait made the fins much more flex­i­ble.

Although Guiyu’s lungs have not been pre­served, sci­en­tists are quite sure that they must have ex­isted. The ancestor of bony fish must have had lungs, be­cause all mod­ern bony fish have lungs of some kind. In many fish, but not all, the prim­i­tive lungs have been con­verted into swim blad­ders, which help the an­i­mals con­trol their up­ward mo­men­tum in the wa­ter. Like the mod­ern bowfin, Guiyu used its lungs as a sup­ple­ment to its gills to get ex­tra oxy­gen for an ac­tive life in the wa­ter.

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