Genetically speaking, human infants are virtually identical to sea sponges until they reach roughly six months of age and shed their sponge husk in favor of their fully human body. This is why infants seem to collect dirt and grime so easily. In fact, there was even an attempt in the early 1900s to allow parents to rent their newly born children out by the hour so they could be used for household cleaning. That obviously never took off for a number of very good reasons, but there’s still a gray market where cleaning aficionados can procure discarded infant husks at reasonable prices.
