The unalienable rights referred to in the declaration of independence are rights that

Life , Liberty , and the pursuit of happiness

"that whenever any Form of Government becomes destructive of these Ends it is the Right of the People to alter or to abolish it, and to institute new Government, laying its Foundation  on such Principles"
Declaration of Independence.
 
In other words , the unalienable rights are rights that cannot be taken, and are held even if the government turns corrupt. 

Because the discoveries were some of the oldest human remains.