Deer Horns are some of the most striking features in the animal kingdom, appearing as elaborate extensions of an animal’s head. A recent study published in Communications Biology sheds light on the origins of these structures, suggesting that they may have evolved from a common ancestor of ruminants 15 to 20 million years ago.
“There’s some sort of genetic predisposition that this family has towards ornamentation,” says Zachary Calamari, an evolutionary biologist at the City University of New York and the American Museum of Natural History.
Which Mammals Have Headgear?
Ruminants With Horns, Antlers, and Ossicones
Ruminants are a group of even-toed hoofed mammals divided into six major groups, four of which have some form of headgear. These include:
- Bovids: Cows, bison, sheep, goats, and African ungulates
- Deer: Moose, elk, and related species
- Pronghorn
- Giraffes: With ossicones rather than horns or antlers
Parallel Evolution or Common Ancestor?
For years, scientists debated whether these animals inherited their headgear from a single ancestor or developed it independently through parallel evolution. To answer this question, Calamari and his colleague John Flynn examined the genomes of living ruminants.
Deer Horns: The Role of Genetics in Horn and Antler Development
How Researchers Analyzed Ruminant Genes
The study focused on RNA, which reveals which genes are active during specific biological processes, such as the early stages of horn or antler development. While fossil RNA is impossible to study, researchers used samples from six young cows and compared their genomes to published data on deer and pigs.
Pigs, a relative of even-toed ungulates, lack headgear, making them a useful comparison group.
Findings on Genetic Similarities in Deer Horns
The analysis revealed that the cow and deer RNA shared similarities in gene expression related to horn and antler growth, while pigs lacked these markers.
“We found that there are genes that are expressed in an analogous pattern,” says Calamari. “Some of these genes could be related to horn and antler formation.”
Did Deer Horns Mammals Share a Common Ancestor?
Evidence of a Single Origin
The similarities in RNA support the idea that ruminants with headgear evolved from a common ancestor rather than independently. This ancestor likely lived 15 to 20 million years ago, during the Miocene epoch, when horns and antlers first appeared in the fossil record.
Possible Appearance of Deer Horns Ancestor
Calamari speculates that this ancestor may have resembled a chevrotain, or mouse deer, a member of the Tragulidae family. These small animals may have had tiny bumps or rudimentary appendages on their heads, laying the foundation for the elaborate headgear seen in modern ruminants.
Exceptions to the Rule: Parallel Evolution in Other Species
Camels and Other Ungulates
Not all headgear traces back to this ruminant ancestor. For example, some mammals related to modern camels, which are not ruminants but even-toed ungulates, developed headgear independently. This suggests that parallel evolution also played a role in the development of horns and antlers in other groups.
Why Understanding Antlers and Horns Matters
Implications for Bone Cancer Research
Studying the rapid growth of antlers could provide valuable insights into bone cancer research. Moose, for example, grow and shed their antlers in a matter of months, a process driven by specialized genes responsible for bone growth.
This research could lead to breakthroughs in understanding and treating bone-related diseases in humans.
Conclusion
The discovery of genetic markers shared among ruminants supports the theory that horns and antlers evolved from a single common ancestor millions of years ago. While the fossil record remains incomplete, this study provides important insights into the evolutionary history of hoofed mammals and the genetic basis for their iconic headgear.
Beyond evolution, understanding the genes responsible for antler growth could also pave the way for advancements in medical research, particularly in the field of bone cancer treatment.
As researchers continue to explore the fossil record and genetics, we may one day uncover more details about the ancient ancestor that gave rise to some of the most recognizable features in the animal kingdom.
Sources:
- Nature: Gene expression supports a single origin of horns and antlers in hoofed mammals
- Discover Magazine: Deer and Other Hoofed Mammals May Have Horns Because of One Ancient Ancestor
