Fontanelles, an incompletely developed mandible, and a small face all are adaptations in humans to allow for... an easy birth a facial skull to cranial skull ratio of 1 : 3 a large fetal brain at birth the fusion of bones prior to birth Buffer solutions will always have a pH of 7. cause a decrease in pH when acids are added to them. cause an increase in pH when acids are added to them. tend to maintain a relatively constant pH . are rarely found in living organisms. .