Common Ancestor Identified – Researchers Decode Ancient Origins of Horns, Antlers and Oxygons

A genetic study supports the hypothesis that the evolution of ruminant horns and antlers is not independent.

From the tiny axicons on a giraffe to the massive antlers of male moose—which can grow as wide as a car—the helmets of hoofed mammals that form are very diverse, and new research suggests that despite the physical differences, the basic features of this bone. Adaptations may have evolved from a common ancestor.

The findings are published in the journal Communication Biology By researchers from the American Museum of Natural History and Baruch College and the CUNY Graduate Center.

„Antlers and antlers are incredibly diverse structures, and scientists have long debated their evolutionary origins,” said Zachary Calamari, an assistant professor at the Baruch College and CUNY Graduate Center and a research associate at the museum. „This genetic research not only brings us closer to solving an evolutionary mystery, but also helps us better understand how bone develops in all mammals.”

A study of modern ruminant species

There are about 170 modern ruminant hoofed mammals species More in the fossil record, along with helmets. The headgear we see today comes in four types: horns, antlers, ossicones, and pronghorns, and they are used in a variety of ways, including protection, recognition of other members of the species, and mating. Until recently, scientists weren’t sure whether these various bony helmets evolved independently in each ruminant group or from a shared common ancestor.

Study author Zachary Calamari scans an elk skull at the American Museum of Natural History. Credit: Matt Shanley/ AMNH

A comparative biology Ph.D. A student at the museum’s Richard Gilder Graduate School, Calamari set out to investigate this question through genetic and computer-based 3D pattern analysis. John Flynn, working with the Frick curator of the Museum of Fossil Mammals, focused on sequencing calamari transcriptomes, the genes expressed in a tissue at a given time, for the cephalopod. Their research supports the idea that all helmeted forms evolved from a common ancestor, paired bone growths from the „forehead” of animals near the frontal bones of the skull.

Insights from genetic research

„Our results provide further evidence that horns originate from the cranial neural crest, the embryonic cell layer that forms the face, rather than from bone-forming cells on the sides and back of the head,” Flynn said. „Notably, these are the same cells that form antlers. Compared to other bone and skin tissue „controls,” the unique patterns of gene expression in cattle antlers and deer antlers provide compelling evidence for a shared origin of basic features of these fascinating bone structures in an ancient ancestor.”

By comparing the newly sequenced cattle antler transcriptome with deer antler and pig skin transcriptomes, Calamari and Flynn confirmed for the first time through transcriptomes that family-specific differences in headgear may have evolved as extensions of a common skeletal structure inherited from a common ancestor.

„In addition to the gene expression patterns that support the single origin of horns and antlers, the regulation of gene expression patterns in these structures may differ from other bones,” Calamari said. „These results help us understand the evolutionary history of horns and antlers, and may also suggest that differences in other cranial appendages, such as oxygons and pronghorns, are extensions of a shared ancestral cranial appendage.”

Note: 20 May 2024, 2024, 2024 Zachary D. Calamari and John J. „Gene expression supports a single origin of horns and antlers in hoofed mammals” by Flynn et al. Communication Biology.
DOI: 10.1038/s42003-024-06134-4

This study was funded in part by the Richard Gilder Graduate School and the National Science Foundation, grant nos. DGE-0966166 and DDIG DEB-1601299.