(The Herald Post) – A new study has revealed that the ancestors of modern mammals managed to evolve into one of the most successful animal lineages by starting small and simple. Early mammal evolution, which began over 300 million years ago, was marked by a reduction in the number of skull bones and a decrease in body size.
An international team of paleontologists published their findings in Communications Biology, using computer simulations and stress analyses to investigate the reasons behind skull simplification in early mammals. Contrary to popular belief, reducing the number of skull bones did not lead to higher bite forces or increased skull strength. Instead, the team found that this simplification allowed for a more efficient redirection of stresses during feeding.
Lead author Dr. Stephan Lautenschlager, Senior Lecturer for Palaeobiology at the University of Birmingham, explained that reducing the number of bones in the skull led to a redistribution of stresses, which in turn may have allowed for an increase in brain size. This change in skull structure, coupled with a decrease in body size, contributed to a dietary switch towards insect consumption, which eventually led to the diversification of mammals.
The study also revealed that early mammals became significantly smaller, with some having a skull length of just 10–12 mm. This miniaturization limited their food sources, causing them to adapt to feeding mostly on insects. The combination of small size, reduced skull bones, and an insect-based diet allowed the ancestors of modern mammals to thrive alongside dinosaurs.
However, it wasn’t until the dinosaurs became extinct at the end of the Cretaceous period, around 66 million years ago, that mammals had the opportunity to diversify further and reach the wide range of body sizes observed today.