One animal which has been pulled back from extinction however, is a species of Galapagos giant tortoise - thanks to the sexual exploits of just this one male.
IndepedentUK reports that Diego is over 100 years old and has fathered some 800 offspring.
Diego weighs almost 13 stones, is just shy of a metre long and 1.5 metres tall.
He was initially found at the San Diego zoo, and his species - Chelonoidis hoodensis - was founded then.
Fifty years ago there were only two males and 12 females on the island and they were so spread out they couldn’t be bred successfully.
He was taken to the Galapagos Islands soon after his discovery, and he now shares his enclosure with six other females.
Washington Tapia, a specialist at Galapagos National park, where Diego resides told AFP:
We did a genetic study and we discovered that he was the father of nearly 40 per cent of the offspring released into the wild on Espanola.
I wouldn't say [the species] is in perfect health, because historical records show there probably used to be more than 5,000 tortoises on the island. But it's a population that's in pretty good shape - and growing, which is the most important.