It’s a well-established scientific principle that as any 3D object, whether a Platonic sphere, a cell, or even an elephant, expands in all directions, its total surface area increases at a slower rate than its volume. This relationship is particularly intriguing because as the object's geometry and shape remain consistent during growth, its surface area tends to increase approximately at the rate of its volume to the power of two-thirds. For centuries, biologists have speculated whether this two-thirds scaling law applies to living organisms, despite their astonishing diversity in shapes and sizes.
If life forms do adhere to this scaling law, it could indicate significant, underlying constraints that are fundamental to the process of evolution. These constraints may influence how various life forms interact with their environments. Recent research has shed light on this topic, particularly focusing on an ancient and diverse lineage of animals: sharks.
A team of researchers recently employed advanced CT scans and digital tools to calculate the surface areas and volumes of over 50 shark species. Their findings, published in the journal Royal Society Open Science, provide compelling empirical evidence supporting the existence of a scaling rule in zoology. The analysis revealed that, similar to the geometric properties of a sphere, the surface area and body mass of sharks indeed conform to the two-thirds scaling law.
If this two-thirds scaling law holds true across other animal groups, it could reflect fundamental biological rules governing heat exchange, metabolism, or development—factors that may significantly constrain the path of evolution. Joel Gayford, a prominent shark biologist at James Cook University in Australia and the lead author of this study, suggests that sharks are an excellent group for studying biological scaling due to their shared overall form and remarkable diversity in size, ecological niches, and body shape.
In his investigations into the morphological evolution of sharks, Gayford observed apparent scaling relationships among their body parts, particularly regarding the sizes of their fins. This observation prompted him to ponder whether more fundamental rules govern the forms that sharks can adopt throughout their evolutionary history.
In conclusion, the recent findings on the scaling laws of sharks not only enhance our understanding of these fascinating creatures but also contribute to a broader comprehension of evolutionary biology. As researchers continue to explore the implications of these findings, we may uncover more about the fundamental principles that shape life on Earth.