Explain how hibernation and migration are responses to an external stimulus

To Explain this we have to look at How animals  and plants live in real life, For Example , a plant would hibernate in the winter , due to the cold , some plants go dormant ( dormant is when a animal or plants action slows down or stop. ) and the external stimulus would be the sun , warming the plant , the plant would still be alive, of course but it would be sort of in a sleep state , Now to answer your question on Migration and how it ties in with this , Lets look at another example for this one : Canadian geese  Fly south for the winter, correct?  well this is mostly due to the cold , Etc ... so when those geese get cold they leave , the External stimulus would be Wind ,temperature , etc ... :)

Many archeologists and anthropologists disagree with dr. thorne's view.  thorne strongly believes that what many calls "homo erectus"  was in fact  homo sapiens,  and that they migrated out of africa almost 2 million years ago and dispersed throughout europe and asia. that's way different  from what scientists have always believed about the evolution of the species.