A recent study published in the journal Communications Biology explores the evolutionary origins of the headgear found in ruminant hoofed mammals. Researchers from the American Museum of Natural History, Baruch College, and the CUNY Graduate Center conducted genomic research to investigate the similarities and differences in the bony adaptations of various species, such as giraffes and moose. By analyzing transcriptomes, which are the genes expressed in a specific tissue at a particular time, the scientists found evidence to suggest that the diverse headgear seen in modern ruminant mammals likely evolved from a common ancestor.
The study focused on approximately 170 modern ruminant hoofed mammal species with various types of headgear, including antlers, horns, ossicones, and pronghorns. These structures serve different purposes, such as defense, recognition of other members of the species, and mating rituals. Previous scientific research had debated whether these bony adaptations evolved independently in each ruminant group or shared a common evolutionary origin. Through genomic and computer-based 3D shape analysis, the researchers found that all forms of ruminant headgear likely evolved as paired bony outgrowths from the “forehead” of the animals, near the frontal bones of the skull.
The researchers, led by Zachary Calamari and John Flynn from the Museum’s Richard Gilder Graduate School, investigated gene expression patterns in cattle horns, deer antlers, and pig skin to confirm that family-specific differences in headgear likely originated from a common ancestral structure. The study found that horns and antlers form from the cranial neural crest, an embryonic cell layer that forms the face, rather than the bones on the sides and back of the head. This discovery suggests that the spectacular bony structures of horns and antlers share fundamental aspects with an ancient ancestor and provide insight into the evolution of these anatomical features.
The results of the study also revealed that the regulation of gene expression patterns in horns and antlers may differ from other bones, indicating unique evolutionary histories for these structures. By comparing gene expression patterns in different ruminant cranial appendages, such as ossicones and pronghorns, the researchers were able to propose that these features are also elaborations on a shared ancestral cranial appendage. The study sheds light on the genetic basis of horn and antler development and the evolutionary history of these iconic headgear seen in ruminant mammals.
Overall, the research contributes to a better understanding of the evolutionary origins of ruminant headgear and provides valuable insights into how bone forms in mammals. The study was funded in part by grants from the Richard Gilder Graduate School and the National Science Foundation. By combining genomic analysis with morphology, the researchers were able to uncover evidence supporting a common ancestry for the diverse headgear seen in modern ruminant mammals, offering new perspectives on the evolution of these striking and functional structures.
