MEXICO CITY — When she walked into an IVF clinic in June, Alin Quintana knew it would be the last time she would try to conceive a child. She had prepared herself spiritually and mentally for the ...

A newborn baby cannot walk, feed itself or even lift its head. Compared with most animals, human babies are remarkably helpless. Yet this dependence is not a weakness; it is an evolutionary advantage.

For decades, scientists have built bizarre-looking apparatuses for babies to traverse. The purpose of these wobbly bridges, narrow paths, and see-through walkways – all suspended over sheer drop offs ...