New study reveals the surprising path to an upright stance
New research from MCZ paleontologists discovered the evolutionary path to walking upright was anything but linear. It was full of unexpected detours, evolutionary experimentation, and dramatic anatomical upheaval. The research was supported by MCZ funding and utilized MCZ specimens.
The adaptive landscape of posture evolution in mammals and their ancestors. Living and fossil species with sprawling vs upright postures occupy different adaptive peaks. Credit: Magdalen Mercado
From the Department of Organismic Biology:
For over 100 years, scientists have wondered: How did mammals evolve from sprawling like lizards to walking tall like cats, dogs—even us?
In a groundbreaking study published in PLOS Biology, Professor Stephanie Pierce and former postdoc Robert Brocklehurst discovered the path was anything but linear, it was full of unexpected detours, evolutionary experimentation, and dramatic anatomical upheaval.
Pierce, Brocklehurst and co-author, Kenneth Angielczyk of Chicago’s Field Museum, analyzed humerus bones from 60+ fossil species and 140+ living animals. Using 3D mapping and biomechanics, they created an “adaptive landscape” of movement with peaks and valleys related to high and low performance of various locomotor postures.
The shocker? They found bursts of innovation, suggesting mammal evolution involved a series of adaptive radiations: major ancestral groups explored a range of forelimb functions and postures—some of which were closer to modern mammals, others not.
The study discovered that mammals have been evolving and radiating into many different niches and habitats throughout their history. One fossil in particular, a close relative of today’s marsupials, showed that fully upright postures evolved relatively late in mammalian history as opposed to previously held hypotheses.