A story written below the skull: silver fox bones may reveal domestication's deeper reach

Domestication leaves its marks slowly, and not always where we think to look.

For decades, the story of domestication has lived in the face, a softer skull, smaller teeth, floppy ears, a curly tail. The cranium has been the easy text. But what happens further down the skeleton? In the bones that carry weight, absorb impact, and remember how an animal moves, that has been harder to read.

A poster presented at Anatomy Connected 2026 in Albuquerque begins to answer that question, and does so by drawing on one of the most consequential experiments in modern biology: the Silver Fox study, launched in 1952 in Northern Russia and now in its seventh decade of selective breeding for behavior.

Presented by Dr. Frederick R. Foster, a postdoctoral scholar at The Ohio State University, the work examines whether the morphological signatures of domestication extend into the postcranial skeleton, specifically into trabecular bone, the internal lattice that records both body size and locomotor behavior. The study was co-authored with Scott Maddux (University of North Texas Health Science Center), Robert Franciscus (University of Iowa), Anastasiya Kharlamova and Lyudmila Trut (Institute of Cytology and Genetics, Siberian Branch, Russian Academy of Sciences), and Habiba Chirchir (The Ohio State University).

The Silver Fox experiment is the bridge that makes a study like this possible. By selectively breeding foxes across three behavioral phenotypes, tame, aggressive, and wild, Drs. Trut, Kharlamova, and their predecessors have produced a dataset no other organism can offer; detailed behavioral, genetic, and morphological data tracked across generations under known selective pressures. Tame individuals show the now-familiar suite of changes: reduced aggression toward humans, altered cranial proportions, gracile features, floppy ears, curly tails, and elevated serotonin. The cranial story is well-established. The postcranial story has been waiting.

Foster and his collaborators used micro-CT to image trabecular bone in the proximal humerus and proximal femur of 30 individuals, five males and five females from each of the three behavioral groups. Using DragonFly 3D software, they measured bone volume fraction (BV/TV), degree of anisotropy (DA), and trabecular thickness, variables that index relative bone mass, the directionality of loading from locomotion, and structural robusticity.

When averaged across each element, the variables did not separate the groups. But the picture changed when the team looked region by region. BV/TV in the femoral head and DA in the femoral neck were higher in wild individuals than in tame ones, a localized, mechanically meaningful difference. The signal was in the architecture.

The finding matters for two reasons. First, it suggests that domestication's reach extends beyond the skull and into the weight-bearing skeleton, where the trace is subtler but real. Second, it shows that these postcranial changes can emerge under strong selective pressure across relatively few generations, a tempo that has implications well beyond foxes.

Foster's team is continuing the work, turning next to the relative contributions of hormones and locomotor behavior to the postcranial changes they have documented. The Silver Fox dataset, built patiently over seventy years, keeps opening doors.
Domestication, it turns out, is a story written in the whole animal. We are still learning to read it.

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