Three young bighorn sheep stand on the cliff. New research shows that males in mammals, including bighorn sheep, have evolved more majestic horns, while females have evolved larger brains. Source: Tom Murphy, Nat Geo Image Collection
Words: Jason Bittel
Imagine a ram slamming down an opponent with its majestic curved horns, each weighing 13 kilograms – what could be more iconic than this?
Do you close your eyes and hear the clanging sound of stags tangling into each other with their large, jagged horns in the dark woods? Or, have you ever been in awe when you saw the big horns of an adult male moose at 1.8 meters?
Arguably, humanity's fascination with heavily armed animals is older than anyone can remember: among the oldest works of art found so far are some depicting the double horns of an ancient buffalo, and others depicting the tusks of a wild boar, which are inscribed in about 440,000 years to 4On the wall of a cave from 550,000 years ago.
However, our fascination with the majesty of antlers, horns and fangs may also lead us to ignore the wonder of the other gender.
In fact, a preprint study published in the journal Beh**ioral Ecology and Sociobiology on the 13th of this month provides the first evidence that while male mammals evolve larger organs to fight and show strength, females of the same species develop larger brains than expected.
I think females are a very important but often overlooked aspect of biology," said Nicole Lopez, the first author of the program and a PhD student at the University of Montana, "because they often look monotonous, dull or sluggish, and nowhere near as delicate [as males]." ”
However, when attention is focused on the top of the male animal's head, the same extraordinary thing may happen inside the female animal's head. Moreover, this finding may upend our perception of the right of female animal mates to choose.
The Kalagadadi Transfrontier Park, which straddles Botswana and South Africa, is home to many springboks (Antidorcas marsupialis). This horned animal is also one of the subjects of interest in this study. Source: Alex Treadway, Nat Geo Image Collection
Mind vs.Muscles
The good news for all the able-bodied males is that the study doesn't say that the bigger the kids, the lower the intelligence level of the lads.
Male animals invest more in their organs and don't become dull. Ted Stankowich, an evolutionary behavioral ecologist and senior author at California State University, Long Beach, clarified.
Contrary to popular belief, when evolution seems to favor larger and larger "headdresses", the size of the male brain remains the same.
At the same time, females seem to be investing more resources in brain size, Stankovic said. While it's unclear whether there is a direct link between these two traits – and if they do, it would give us a lot of information – research suggests that the two are related.
To obtain data and understand the interrelationship of these features, Stankovic, Lopez and co-author Jonathon Moore Tupas visited seven museums, where they measured the skull, brain volume and organ size of 413 specimens of 29 species of ungulates. These specimens range from deer, caribou, and moose to goats, sheep, and antelopes.
A bighorn sheep (Ovis canadensis) nudges another younger, ram from behind. Source: Robbie George, Nat Geo Image Collection
Two male bighorn sheep wrestle on a cliff. Researchers say that humans have a cultural obsession with males using their horns as **, which leads us to ignore the equally interesting biological traits of females. Source: Barrett Hedges, Nat Geo Image Collection
It took us several years to measure those 400-odd specimens. "Lopez.
As for why while females massively increase gray matter in their brains, males are vigorously developing**, scientists are still trying to find out.
We think it's like this: Males are more invested in *** because it makes them stand out more to females, and maybe then their social systems become more complex," Stankovic said, "but females may need bigger brains to figure out who they should choose to mate with and how to dominate their social system." ”
Ummat Somjee, an evolutionary biologist at the University of Texas in Austin and the Smithsonian Tropical Research Institute in Panama, pointed to several limitations to the study. For example, as the authors mention, brain volume does not necessarily represent the level of intelligence. Reaching this conclusion would require obtaining behavioral data for each of the relevant breeds, which would be much more difficult than existing studies.
Similarly, while praising the authors for examining as many species as possible, he also noted that the 29 species selected for the study represent only a small fraction of the ungulates that have ** on Earth. Who can be sure that when other varieties with antlers, horns or tusks are evaluated, the pattern that is now coming true still holds?
Even so, Somji, who specializes in insects and is not involved in research, called the conclusion "a super interesting idea with huge implications." ”
In East Africa, wildebeest leaps into the Mara River. Picture: Charlie Hamilton James
Glory deserved
In a way, it is not surprising that humans are fascinated by animal organs. After all, attracting attention is the goal of many of these structural evolutions, Somji said.
We are fascinated, deeply seduced, and misled by them. He said.
For example, Somji says, we found that male cervids (such as deer, moose and red deer) develop temporary osteoporosis every year, a period during which they divert nutrients from their bones to develop horns. The new study also shows that the brain-muscle effect is more pronounced in horned cervids than in bovids; On the other hand, the seasonal characteristics of the casse's crown may be partly responsible for this effect.
For almost 500 years, wild deer roamed the land of Knole House, the home of a former British archbishop. New research shows that male antlers are unusually strongly correlated with the evolution of the female brain. Source: Jim Richardson, Nat Geo Image Collection
It's a magical natural phenomenon. It's weird, it's unusual," Somji said of the rapid growth and shedding of antlers, "but I think it's also very strange that people have missed the changes in females." ”
For example, females also use large amounts of calcium, sulfur and other nutrients in their bodies to give birth to entire offspring in the womb. And naturally, any tissue that continues to form antlers, horns, or tusks is produced by these females in the first place.
In Lopez's view, much of the scientific literature focuses on the struggle between males to understand the phenomenon of sexual selection (i.e., traits that are effective in mate selection) in these species. After all, the mainstream theory has long held that only the largest and strongest males can have females.
But the fact may be that we didn't test it in the right way and therefore failed to find that (the female) does indeed have some kind of decision over the male with whom it ends up mating. Lopez said.
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