I apologize up front, as I realize that those terms aren’t politically correct; it’s the limitations of a thread title.
That said, Why don’t you ever see elephants the size of cows or dolphins the size of dogs?
Dwarf horses are an obvious example. The also line breed them to produce ever smaller ones. There are also dwarf dogs, cats and cattle so I imagine, at least for mammals it’s a genetic issue that manifests across species. Re “seeing them” dwarfism generally comes with other physical issues so I would imagine the survival rate without human assistance for wild dwarf animals is probably pretty low.
Achondroplasia can affect many animals - dogs, for instance, and cats - the Internet-famous Lil Bub is an achondroplastic cat.
Outside of achondroplasia, there are numerous breeds of dog bred to be short-legged - Corgis, dachshunds, etc. Wikipedia has an article on the extinct Ancon sheep breed which was apparently bred for shortness.
Dwarf elephant in Sri Lanka.
Dwarfism is not uncommon among animals of all types. There’s a concept called insular (popularly island) dwarfism, where the lack of resources selects for smaller animals.
Basically, if you just google dwarf animals you turn up lots and lots of examples.
This page has a bunch of interesting dwarf species. So does this page.
In the wild, genetic carriers of dwarfism would be unlikely to reproduce more of their kind, against breeding competition and simple capability of survival. What would be the life expectancy of a short giraffe? The examples shown in above posts are of domesticated animals, in which human agency has selected dwarf stock.
Those that do for some reason (e.g. insularity) are taxonomically thought of as a different species or subspecies. I think this discussion is about dwarves in a general normal population.
Do you have me on Ignore? None of the examples in my links are domesticated species.
Dwarf ponys (ponies?) as pets are a thing, apparently.
No cite; very recently I saw a photo spread on line, and I don’t want to find it again. The revulsion and disgust I felt was actually quite startling – apparently the three emotions are compatible in quick succession.
They are bred specifically for this genetic composition.
Re “Dwarf” and “midget”:
They are the correct words.
Animals don’t have politics to be correct. (Cf. “The Fly.”)
[ETA to post on ponys (that spelling looks right): it may be in an Exapno link; my machine choked on one.
No, but I’m certainly thinking about it. Note that I said “the above posts” – plural.
Wait, you felt revulsion, disgust and startled(ness) because… people keep ponies as pets?
Yep, “the above posts”. Not “the posts of Blurgle and astro,” but “the above posts.” That has one meaning: all of them.
From the little I know about dwarfism, it’s certainly not always something that’s passed down as a genetic trait, but often the result of a mutation in the egg of the mother or the sperm of the father.
The vast majority of people born with dwarfism actually had parents who were of average height.
Does this work the same way among animals in the wild? I honestly have no idea (though it looks like it)… but if so, you certainly wouldn’t need one or both parents afflicted with dwarfism to “reproduce more of their kind”.
The link in Blurgle’s post says that Osteochondrodysplasia and Achondroplasia are genetically acquired. Further, it says
Medicinenetsays
I think the distinction that you are looking for is not so much “wild” vs “domsticated”, it lies in the genetics. Dwarfism may arise suddenly in a single individual without selection; or it may evolve gradually due to selection. Either case may occur in both wild and domesticated populations; when selection is involved, it may be natural selection (most dwarf animals) or artificial selection (small dogs), these are genetically similar processes.
Achondroplasia is caused by a mutation in a single gene. The mutation in that gene may be inherited; but more commonly the parents do not carry the mutation, it is sporadic. Thus, achondroplasia arises suddenly in individuals within a larger population. A single genetic mutation has a large phenotypic effect, so a large change occurs randomly and abruptly without prior selection.
However, quantitative traits such as height and weight are polygenic. They are influenced by a large number of genetic loci, most with small effect. Generally, such traits can respond quickly to selection (natural or articificial) over a few generations without waiting for a suitable new mutation to arise by chance, since there is standing genetic variation available in a population. When dog breeders select for a small dog, they cross pairs of dogs, and select the smallest pups. The small pups carry new combinations of gene variants that already exist in the population. Selection for polygenic quantitative traits can proceed quite quickly until the standing variation in the population is exhausted. In other words, you get to some minimum size within a few generations when you find the combination of existing genetic variants that gives the smallest possible animal. To go smaller requires new mutations to arise by chance, but this takes more time and luck. The genetics of natural selection are similar to artificial selection, although generally slower, because the pressure of natural selection is rarely so intense as artificial selection.
In both casts & dogs, there is often an offspring that is the ‘runt of the litter’.
But these generally require significant help from a human to survive – in the wild they would mostly die in the first day or two.
And I’m not sure they would count as Midgets or Dwarves, because there is no genetic component to their size – if they survive, they produce offspring of normal size.
Yes, runts are usually attributable to environment, not genetics. That includes the fetal development environment in the womb. If you’re trying to develop a small dog breed, you won’t get anywhere by selecting runts.
But those are a different species, not individuals within a species that are normally much larger. Reading the thread title, it looks like the OP is asking for individuals within a given species.
I think the distinction is best stated as:
(1) (OP’s question) A single genetic mutation with major effect giving rise sporadically to dwarf mutant individuals within a non-dwarf population. No prior selection is involved, although the mutant phenotype will almost certainly have different fitness, so selection will have subsequent effect.
(2) An entire population of dwarf animals that evolved from an ancestral population of larger animals over multiple generations through selection pressure (natural or artificial) for smaller size. The dwarf population may or may not eventually evolve into a distinct dwarf species.
And note the general principle that mutations occur to individuals within a population; evolution acts on populations.
Yes. And I think it’s clear the OP is asking about #1. It’s unfortunate that we use the word ambiguously like that.