:how does the constitution, especially in the bill of rights and the 14th amendment, guarantee equality under the law

They guarantee equality because the bill of rights enumerates things that we all have rights to like the freedom of speech and similar stuff. The 14th amendment is one of the reconstruction amendments and was important for giving everyone equal rights regardless of skin color or ethnicity. Women had to wait a bit more though.

Because the discoveries were some of the oldest human remains.