Killing the biggest males for food would have left younger males engaged in pitched battles to replace them, violent affairs that could have affected the normally stable animal societies, University of Michigan paleontologist Daniel Fisher said.
He cites as evidence puncture wounds from tusks and smashed bones found in fossils of female mastodons.
Similar affects can be observed in modern elephant populations when poachers kill the large male bulls that keep younger males in line.
Humans may have had the same effect on mastodons, Fisher said.
"Humans were the main driver of extinction, but when you look deeper into the complexity of that something very interesting starts to appear," he told The Daily Telegraph.
"The social structures of these animals were severely degraded as a result of the loss of mature males and in my view forms part of the extinction process," he said.
He emphasized the analogy with modern elephants.
The normal structure of elephant society is one where the old bulls keep the younger males in check," he said. "When the big bulls are pulled out of the picture, all hell breaks loose."