A recent research project concerned with the study of variations within a certain fish species around the world has led to the unexpected outcome of shedding new light on how upright gait in modern humans might have evolved.
The fish in question, the threespine stickleback, is known for having radically different evolutionary adaptations depending on the wildly disparate environments in which it is found globally. The little fish has demonstrated its ability to match its skeletal structure to its environment, and the gene expression variation that facilitates the change in the stickleback may have played a role in early primates transitioning from a prehensile foot to one that was capable of withstanding the weight of bipedal motion.
Research scientists from Huntsville, Alabama’s HudsonAlpha Institute for Biotechnology and California’s Stanford University School of Medicine who were involved in the study say that it’s not exactly common to have a project that focuses on fish evolution and anatomy bear fruit in the study of human development. However, Stanford developmental biology editor and senior author of the study Dr. David Kingsley remarked in a press release that the process behind both the stickleback’s ability to change its skeletal armor and the development of hind limbs in primates and humans could be altered in the same way. This process revolves around changing the molecule expression levels of bone morphogenetic proteins, and Dr. Kingsley added that the change was likely a contributory factor in the evolution of our upright gait.
Sticklebacks are renowned for their exterior armor of bony spines and plates that are large and thick in marine environments yet smaller and lighter in regions that are dominated by freshwater. Investigators examined the genome of the fish by comparing 11 pairs of fish from both marine and freshwater environments. Researchers discovered that the gene controlling a specific bone morphogenetic protein, known as GDF6, was more active in freshwater versions of the stickleback. Intrigued by the role that GDF6 expression levels might have played in the skeletal development of humanity, the researchers began comparing genetic differences between chimpanzees and humans, only to discover that the GDF6 gene coincided with two primary genome differences between chimps and humans where the latter had lost regulatory regions in comparison to their evolutionary cousins.
The researchers then investigated further by using regulatory DNA from chimps to control protein production in mice. The results were clear: the protein was expressed specifically in the hind limbs and the lateral toes, but was not present in the fore limbs of the mice – or the big toes in their hind limbs. Meanwhile, mice that had their genes altered to eliminate their ability to produce GDF6 had shorter than normal toes as well as smaller than normal skull bones, indicating that the gene might have a crucial role in the evolution and development of limbs.
The study, which was recently published in the journal Cell, can be found here
Image courtesy of Wikimedia Commons user: Joxemai