Homo sapiens environment of evolutionary adaptedness bathed the infant in rich environmental stimulation, both social and non-social. Because of this, 21st century babies still thrive best in the context of diverse and complex sensory-motor experience, and when loving adults and older children respond to the baby and grow increasingly long and complex social reciprocity chains. The latest neuroscience proposes the primacy of motor development for optimal developmental outcomes. Motor development is enhanced by experiences of postural variability and sensory-motor stimulation from the beginning of life. Dr Pamela Douglas and Honorary Associate Professor Peter Hill reflect upon the potential risks of infant sleep training practices, which problematise sensory-motor stimulation, during a time of social isolation. Pam is a GP-researcher and founder of the evidence-based Neuroprotective Developmental Care (or 'Possums') programs www.possumsonline.com. She is also author of The discontented little baby book: all you need to know about feeds, sleep, and crying.