The Evolution of Chordates

Your ears actually started out as fish gills. It's wild, but all chordates,

including you, share the same four traits as embryos: a supportive notochord, a nerve cord,

a tail, and pharyngeal slits. For us, those slits become parts of our head

and neck. Evolution then went into overdrive. First came backbones, creating vertebrates.

Then, jaws appeared, a huge advantage for hunting. Next,

lobe-finned fish like Tiktaalik crawled onto land, developing limbs and becoming the

first tetrapods. Finally, the amniotic egg allowed animals to leave the water

for good, leading to reptiles, birds, and us mammals.