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In the beginning, living systems were relatively simple and depended upon only a small number of macromolecules for metabolic activity and continued existence. Evolutionary progress entailed the acquisition of new macromolecules and metabolic processes, eventually resulting in the great variety and biochemical complexity of the life forms that exist today.Early biological evolution required the creation of new metabolic machinery encoded in new deoxyribonucleic acid (DNA). However, much subsequent evolutionary change has depended primarily upon the modification and elaboration of preexisting components, particularly the DNA

BackgroundPerinatal exposure to low-doses of bisphenol A (BPA) results in alterations in the ovary, uterus, and mammary glands and in a sexually dimorphic region of the brain known to be important for estrous cyclicity.ObjectivesWe aimed to determine whether perinatal exposure to environmentally relevant doses of BPA alters reproductive capacity.MethodsFemale CD-1 mice that were exposed to BPA at 0, 25 ng, 250 ng, or 25 μg/kg body weight (BW)/day or diethylstilbestrol (DES) at 10 ng/kg BW/day (positive control) from gestational day 8 through day 16 of lactation were continuously housed with proven breeder males for 32 weeks starting at 2 months of age. At each delivery, pups born to these mating pairs were removed. The cumulative number of pups, number of deliveries, and litter size were recorded. The purity of the BPA used in this and our previous studies was assessed using HPLC, mass spectrometry, and nuclear magnetic resonance.ResultsThe forced breeding experiment revealed a decrease in the cumulative number of pups, observed as a nonmonotonic dose–response effect, and a decline in fertility and fecundity over time in female mice exposed perinatally to BPA. The BPA was 97% pure, with no evidence of contamination by other phenolic compounds.ConclusionsPerinatal exposure to BPA leads to a dose-dependent decline in the reproductive capacity of female mice. The effects on the cumulative number of pups are comparable to those previously reported in mice developmentally exposed to DES, a compound well known to impair reproduction in women. This association suggests the possibility that early BPA exposure may also affect reproductive capacity in women.

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