Scientists say the species survived in isolation for 7,000 years before going extinct.
The boy spotted the tooth in the grounds of a hotel owned by his relatives.
Researchers inserted the mammoth nuclei into mouse ova where they saw "signs of biological activities."
Does the foot-long fragment come from a mammoth or a mastodon?
A woolly mammoth bone washed up on the beach in Scotland.
Evidence suggests ancient humans may have hunted the mammoth and then stored the meat at the bottom of a pond.
It could be yours for about the price of a small apartment in Brooklyn.
Mammoth ivory, like modern elephant ivory, is durable and doesn't splinter easily, and so makes a good spear for hunting.