Spontaneous lactation is an adaptive result of pseudopregnancy

@article{Creel1991SpontaneousLI,
  title={Spontaneous lactation is an adaptive result of pseudopregnancy},
  author={Scott R. Creel and Steven L. Monfort and David E. Wildt and Peter M. Waser},
  journal={Nature},
  year={1991},
  volume={351},
  pages={660-662}
}
LACTATION is almost exclusively associated with pregnancy and giving birth. Although lactation can be induced without a preceding pregnancy in some species, this requires exogenous hormones, artificially intense or extended suckling or both1,2. Spontaneous lactation, lactation by females that have neither been pregnant nor experimentally manipulated, is extremely unusual among eutherians3–8. Among nondomesticated animals, spontaneous lactation has been observed repeatedly only in the dwarf… 

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