Alternatively, early photoperiod may have non-adaptive effects on development. Stressed pregnant rats have offspring with altered physiologies and behavior including altered dopamine levels [103]–[106]. Early rearing environment of rhesus monkeys is associated with lower amine activity, including that of HVA [107]. Studies in rats and mice show that changes in light exposure early in life is related to sensitivity to light later in life [reviewed in 23]. These studies give reason to believe that developing human brains may be easily affected by early photoperiod. In such a long-lived species, these effects could represent compensation for early perturbations in development, rather than adaptive tracks for later-life behaviors based on early photoperiod.
