Prior to Leonard Hayflick's discovery, it was believed that vertebrate cells had an unlimited potential to replicate. Alexis Carrel, a Nobel prize-winning surgeon, had stated "that all cells explanted in tissue culture are immortal, and that the lack of continuous cell replication was due to ignorance on how best to cultivate the cells". He claimed to have cultivated fibroblasts from the hearts of chickens (which typically live 5 to 10 years) and to have kept the culture growing for 34 years.