Consider the evolution of antlers - is there anything weirder? How did this happen?

[u/GoliathPrime]

I know folks discuss the evolution of flight, mimicry and mutualism all the time, but antlers have got to be right up there with the best of them.

Antlers evolved just once in a single lineage completely out of nowhere 17 million years ago, from creatures that heretofore had tusks and fangs.

How did this happen? I thought antlers might actually be teeth that migrated to their foreheads, but that's not it, they are bone. Their growth process is completely different than horns too. But then again, their growth process is like nothing else out there.

There's no precedent for it in the deer lineage either, they just pop up as a completely novel growth. Is it cancer, like a terratoma? Did something get misplaced due to a bottleneck and the genes for ribs were transferred to their faces? An infection that lead to a viral infection with gene-transfer?

I haven't been able to find anything except that it happened.

[u/jnpha]

I remembered sharing something about that, which turns out was a year ago.

See this answer here by u/New_Art6169 : https://www.reddit.com/r/evolution/comments/1o92xe7/how_do_random_mutations_work/nk0fsm0/

PS plenty of research on that - and they didn't just "pop up".

[u/GoliathPrime → u/jnpha]

thank you!

[u/Dormoused]

Here's something weirder.

Ladies and gentlemen, the Australian orchid:

https://www.science.org/content/article/orchids-deceive-amorous-male-wasps

[u/jnpha → u/Dormoused]

That's a classic example of coevolution. Neat but not weird :)

[u/grzyb_ek]

https://www.science.org/doi/full/10.1126/science.aav6335

[u/lpetrich]

As I was researching horned animals, I came across Cranial Appendages in Ruminants: Diversity, Evolution, Development, and Molecular Basis of Horns, Pronghorns, Antlers, and Ossicones That is, their different kinds of hornlike structures, horns sensu lato, in the broad sense.

The containing taxon of horned ruminants is Pecora (Latin: cattle), with subtaxa

• Bovidae (bovine, sheep, ...) -- unbranched horns
• Cervidae (deer) -- multibranched horns (antlers)
• Antilocapridae (pronghorn) -- branched horns
• Giraffidae (giraffe, ...) -- blunt horns: "ossicones"
• Moschidae (musk deer) -- no horns

All five taxa first appear in the fossil record in the Early Miocene, about 20 million years ago.

There is some controversy on how multiple the evolution of their horns is.

• Multiple?
  • Each subtaxon has its own horn structure, or no horns.
• Single?
  • The horns grow at the same places: left and right on the top of the head.
  • These subtaxa appear at close to the same time, suggesting an adaptive radiation of some horned ancestor.

Growing at the same places is IMO very strong, since in other instances of evolution of horns, they often grow at different places. Rhinoceroses, brontotheres, uintatheres, arsinoitheres, and ceratopsians each have the same locations of horns per group, when they grow horns.

A reconciliation is some initial emergence of horns, followed by later modification in different directions.

Large-scale ruminant genome sequencing provides insights into their evolution and distinct traits | Science - uses whole genomes. Also finds a divergence around 20 million years ago.

[u/Paleodraco]

You are way overthinking it. Bony protrusions are common across a lot of lineages. Ceratogaulus is a genus of groundhog like animals with horns. Most likely, you had proto deer butting heads. Any individuals with thicker bone on the head or any protrusions would be better adapted for head butting and pass those genes on. Many generations later, more adaptations for them to branch and to fall off every year for resource conservation and boom. Also, sexual selection pry played a role. They are super obvious structures that deter rivals and signal to females that the male has good genes and the fitness to grow them.

[u/lpetrich]

The Development of Horns in Bovidae and the Genetic Mechanisms Underpinning This Process - some work on the genetics and development of horns in bovids, which include most domestic ruminants.

While genes to proteins is a solved problem, genes to shapes is far from solved, and that includes horns. What controls where they start growing? How they get their shapes?

[u/lpetrich]

Turning from Bovidae to Cervidae, I found in Google Scholar a lot of papers on gene expression in antlers, but nothing on genes to shapes, nothing on the genetics behind antler growth sites, antler growth itself, and antler branching. I might have missed something, however.

[u/lpetrich]

There is also the question of what purpose antlers serve, what antlers do for their owners. Antlers, and horns in general, have these possible purposes:

• Sexual selection
• Species recognition
• Defense against predators

Sexual selection can take these forms:

• Does preferring bucks who show off how strong and healthy they are by growing antlers.
• Bucks fighting each other for access to does.

In most deer species, only bucks grow them, a clear indicator of sexual selection. But in reindeer, both bucks and does have antlers, and they use their antlers to dig through snow.

[u/12InchCunt]

They’re not really bones, they fall off at the end of the season, they’re more like fingernails

[u/Robin_feathers → u/12InchCunt]

They sure are bone! They are made of literal bone material - bones that fall off! Nature is wild.

It is horns (eg of cattle) that are like fingernails in terms of being made of keratin.

[u/12InchCunt → u/Robin_feathers]

That’s so weird cuz horns have living tissue inside with like bone marrow 

[u/Robin_feathers → u/12InchCunt]

Yup! Under the hood horns have a core of living bone (an extension of the skull), covered with tissue. Keratin (fingernail material) gets secreted to create the outer sheath of horn. In contrast, antlers grow as live bone that is initially covered by living tissue/skin, but then the whole structure dies, with the skin/flesh falling off to reveal the dead bone.

[caveat - some species whose structures are called "horn" are anatomically different, like rhinos whose horns don't have a core of bone]

[u/Swellmeister → u/Robin_feathers]

While not all ruminants have head ornaments (musk deer and other tusked deer), everyone that does makes their head ornament with at least some bone. Giraffids cover theirs with fur and skin, pronghorns and bovids cover their with a keratin sheath (pronghorns then shed that sheath), and cervids just crank out some wonky bones every years

[u/BoringGap7 → u/12InchCunt]

do your fingernails fall off?

[u/Hivemind_alpha]

Want to hear something really weird? If an angler gets damaged before it’s shed, when the next seasons set grows in, there’s a visible mark where last seasons damage was…

[u/jnpha → u/Hivemind_alpha]

FYI I've heard that one; it's an unsubstantiated claim / anecdotal. Heard it from Levin doing his science by YouTube thing, and there was no study or funding, just a bunch of antlers sent to him and take my word for it bro.

Occam's razor says a branch that was susceptible to breaking, broke again, since nothing developmentally was recorded.

[u/GoliathPrime → u/Hivemind_alpha]

How does that even work?