Through the motions

A strange feeling of relief and gratification floods through Feedback as, after years of straining, science finally plops out an answer as to how wombats produce cube-shaped faeces.

This question has been hanging in the air for some time, with preliminary results having emerged in 2018. But the job remained half-done until the publication by bioengineer Patricia Yang and her colleagues of the definitive paper, “Intestines of non-uniform stiffness mold the corners of wombat feces”, in the journal Soft Matter. Yang’s previous research record includes finding that all mammals weighing over 3 kilograms clear their bladders in 21 seconds (plus or minus 13 seconds), regardless of body size.

Now, co-opting the massed ranks of the Australian wombat research establishment to supply intestines for dissection and employing some hardcore fluid dynamics modelling, her team concludes that wombat number twos require peristaltic contractions of gut regions varying by a factor of two in thickness and four in stiffness to produce pellets with flat faces and sharp corners.

As ever, Feedback salutes the onward march of science. But we are left with that age-old criticism: it’s very good at telling us the how, but less good at telling us the why.