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Index][Thread Index][Subject Index][Author Index] What is
difficult, however, is nourishing unborn young the way mammals
do. A female mammal allows each embryo to burrow deep into the
wall of her womb, where it takes nutrients straight from her
blood. This intimate arrangement was long thought to have only
evolved once, in mammals. Not so. It now appears that it evolved
at least twice: once in mammals, and once in an obscure African
lizard called Trachylepis ivensii.