He can't answer why the chicken crossed the road, but biology professor Mark Haussman knows why certain chickens might get more stressed out than others, and why those chickens are predisposed to early aging.

Haussmann and a group of researchers set out to discover whether aging - or a predisposition to it - begins in the very earliest stages of development. In their study, Haussmann, two student researchers and collaborators from the University of Illinois showed that chickens that received stress hormones during their fetal development were more apt to "overreact" to stress later in life. The same chickens also took a longer time to recover from stress and displayed early signs of aging.

"When those offspring grow up, they have a hyperactive stress response," he said. "This means that their own stress hormones are high for longer and it is harder to turn that stress response off, which causes health risks in the long term."

The chickens in the study that were exposed to stress hormones in the egg stage also had higher levels of oxidative damage and displayed shorter telomere length in their DNA, indicating premature or advanced age. "The cells in the chickens with the hyperactive response actually were aging much more quickly than you'd expect, in some cases five or 10 years faster," he said.

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