Amphioxus

The lancelet, also known as amphioxus, provide evidence or indications about the origins of vertebrates. Lancelets serves as a way for scientists to trace how vertebrates have evolved and adapted over time.  The lancelet or amphioxus is the precursor to all higher objects.  Scientists use amphioxus to show how old genes are used for new functions in vertebrates. 

Mitochondrial Eve

Mitochondrial Eve is estimated to have lived around 200,000 years ago in East Central Africa. Through migration of the mitochondrial eve's offspring, you can trace the mitochondrial DNA in every person through their lineage on their mother's side.  You can trace the mitochondrial DNA so far back that every person is connected through the Mitochondrial Eve.