Evolution is not a particularly fast optimizer, on the scale of human perception.
Any early branch can infinitely on that confined branch. It means the billions of other possible branches may never be explored even given infinite time.
Counter would be the evolutionary fill theory where any branch can become any other branch given an environment.
Evolution seems more like building a tree where mostly all you can do is ascend the tree and add finer detail, leaving the trunk and branches (our evolutionary history) in place. It seems unlikely that, say, vertebrates are in the future going to "undo" the major evolutionary developments of the past and lose their skeleton, body symmetry, number of limbs, lungs, alimentary canal, nervous system, brain, etc. We see things like these developing in the evolutionary tree and mostly staying in place once created. Sure some fins turned to limbs, some gills to ears, but once things like that happened they seem to stay in place.
I wonder what evolution would look like if we could see it sped up from the origin of life to billions of years into the future? A building up of complexity to begin with, but those major branches of the evolutionary tree remaining pretty stable it would seem. Continual ongoing change, but of smaller and smaller scope, perhaps - building on what came before.
Try looking at whale skeletons over time. What isn't beneficial gets undone.
https://en.wikipedia.org/wiki/Recurrent_laryngeal_nerve#Evid...
Basically, your sex drive is the main search optimization :p
Edit: This is essentially how genetic algorithms in computer science work. They’re often remarkably effective at finding good solutions without needing brute force.
There's lots of processes that favor certain patterns over others, only considering the biochemistry of the cell, not even the fitness of the animal.
I didn't know this. I suspect this evolved because some amino acids are more useful than others, and increasing the probability of encoding for them was beneficial.
https://press.uni-mainz.de/determining-sex-in-ants/
somehow a male ant has one set of chromosomes while the female ant has two sets of chromosomes. So a male ant sperm must contain enough information to make a complete male? Then when they mate with the female of the other species, the females egg actually gets blanked out so to speak, containing none of the females own genetic material. Then the male sperm fertilizes the egg with one set of chromosomes producing a male offspring that is a clone?
In normal ants, the queen can produce haploid (single set of chromosomes) unfertilized eggs that hatch into males. Normal ant males are haploid. They don't have a father, they can not have sons (but the do have a grandfather, and their daughters will make them grandsons). When the ant queen decides to produce sons, she will make haploid eggs via meiosis as normal, and just won't fertilize them with male sperm.
Ants don't have sex chromosomes. An individual with a single set of chromosomes (haploid) is a male, an individual with double set of chromosomes (diploid) is a female. Ant males are almost like sperm cells that grew into multicellular organisms.
https://en.wikipedia.org/wiki/Haplodiploidy
Now, a Messor ibericus queen can produce eggs with her own genetic material removed, and fertilize these with the single set of chromosomes from a Messor structor male. (It will still have the mitochondria and mitochondrial DNA from the queen.) And because the male only has a single set of chromosomes, the sperm and the resulting offspring has an identical single copy of the father's genetic material (except the mitochondria that came from the mother). So the son is a clone of the father (except for mitochondria).
The queen can also mate with males of her own species, contributing half of her own chromosomes to combine with the full single set of the male chromosomes, to produce to-be-queen female offspring. Here we have the normal genetic recombination (though only on the mother's side) to keep the evolutionary benefits of the variation from sexual reproduction.
The interesting part is whether M. ibericus queens do actively remove their own genetic from eggs fertilized with builder sperm. Why would they do this?
M. ibericus queens produce ibericus×structor hybrids as infertile female worker ants.
M. ibericus queens produce structor males, so future queens can keep producing the hybrid worker ants.
My guess is, maybe there is some benefit having the workers to be hybrids and not pure ibericus ("hybrid vigor" [1]). So it's worth the effort of keeping the structor males along, to be able to produce the hybrid workers. But I think the pure ibericus genes in the line of queens are in control.
Having genetic differences between males and females is mostly a bird and mammal thing, at least among vertebrates.
Also: the configuration and function of sex chromosomes is not consistent even within mammals. There are a number of species - primarily rodents - with unusual sex-determining systems, like species with XX/X0 (i.e. where males have an unpaired X chromosome) or even X0/X0.
(It’s possible that this was just a Greek quirk and never made it to Palestine, I suppose.)
https://www.newyorker.com/magazine/2020/05/25/where-do-eels-...
https://www.sciencedirect.com/science/article/pii/S003257911...
In some though not all such species, there are no known male examples _at all_ (though in reptiles some forms of parthenogenesis can produce males).
https://www.biblegateway.com/passage/?search=Leviticus%2011:...
Plants. Fungi.
I don't have the space to help on your other issues.
This confuses me too.
Did the queen once mate with one of these males and save the sperm for two years? Or are the queens somehow born with a copy of the genetic material.
Or does the old queen produce one, which mates with the new queen, and then dies off. And the new queen is able to hold onto that sperm for years (forever?). And they only produce a handful of males for this purpose?
Also why is it so difficult to have males in lab conditions?
This ability of the female to give birth to "multiple species" seems to me best understood as the two "species" not having yet actually become distinct, since the only meaningful definition of speciation is when two sub-populations of a species have genetically drifted so far apart that they can no longer successfully interbreed and produce fertile young.
During the process of speciation (one species splitting into two) there are going to be various messy half-way stages such as lions and tigers still able to interbreed and so not fully speciated (even if well along, and not going to typically interbreed), horses and donkeys still able to interbreed but producing infertile young (mules), and these ants in this strange state where interbreeding apparently only results in males. It would be cool to be able to speed up the evolutionary timescale to see the process happen, but what we have here is like a still frame from a movie.
Queens don't actually mate to produce male offspring.
Females are Diploid: They are created from a fertilized egg. They have two sets of chromosomes - one set from the mother (the queen) and one from the father's sperm, which the queen releases from the spermatheca when she wants a female.
Males are Haploid: They are created from an unfertilized egg. They have only one set of chromosomes from the queen located in the nucleas of the egg. The queen does not release the male's sperm when she wants a male offspring. They have no father. They hatch from an egg that contains only the mother's genetic material, meaning they are essentially a haploid (single chromosome set) version of the queen.
The M. ibiricus queen produces 2 kinds of offspring with the M. structor:
Sterile Female Hybrid Workers: These are produced in the standard way. The queen lays an egg (containing her genes) and fertilizes it with the sperm from the M. structor male. The resulting worker has DNA from both parents. It's a true hybrid. There is no "dominance"; it's a merger of two different species' DNA.
Fertile Male M.structor Clones: This is where things get really bizzare.
Remember that in the normal case:
- The queen does not use a male's sperm to produce male offspring.
- Joining both DNA always results in a female (males do not have two sets of chromosomes)
There can only be one conclusion. The queen creates this special clone from the male's DNA only, probably by somehow purging her DNA from the nucleus of her egg.
For example, American bison and domesticated cattle can interbreed to produce fertile female beefalos, but the males are sterile. Are domesticated cattle the same species as buffalo?
Then there's ring species: populations of animals where population A can interbreed with populations B and D, but not with C, but C can interbreed with B and D. (often the rings are larger than that). For example, the genus Ensatina salamanders here in California can interbreed with neighboring populations as you go around the mountains, but if you drove one from one side of the central valley to the other it couldn't interbreed. We've mostly decided in that case to call them a bunch of different species, but it's a weird case.
Shit gets even weirder when you leave the animal kingdom. All varieties of pepper will cross pollinate. Bacteria just sort of spread their genetic material to anything that's nearby. Don't even get me started on the absurdity of declaring all the asexually reproducing organisms as being single species individuals.
Basically, a species is a group of animals that has enough of the following characteristics that biologists can agree they're sufficiently different things:
1) They appear distinct from other things
2) They exclusively select mates from their group
3) They exclusively produce fertile offspring with their group
4) They occupy a distinct niche in their ecosystem
5) They are more genetically similar to other members of their group than to other things we consider distinct species
6) Their common ancestor with another group we identify as a species is extinct and considered a different species
7) They really seem like they should be a speciesI hadn't really considered the definition of asexually reproducing species - it seems that things are much more clear cut for ones that sexually reproduce since then we can use the more clear cut "point of no return" definition.
I suppose in cases like beefalos and mules, or these ring species, this "point of no return" comes down to is there any path for to the DNA of these divergent animals to recombine, so a fertile female beefalo (or the occasional fertile female mule) still provides that chance.
It seems that in general it's rare for widely divergent animals like zebras and horses to interbreed in the wild, but apparently western wolf-coyote hybrids are not that uncommon, so it's more than just a theoretical possibility. Who knows, maybe global warming will force polar bears to adapt to warmer climates and increasingly interbreed with grizzlies.
In reality, we first categorized life into species because they either looked different or we found them exclusively in different places, and only centuries later did we attempt to figure out exactly why and how this was the case and reverse engineer some sensible definition onto the pre-existing categories, but it turns out there is no single definition that works universally and has zero exceptions. It's frustrating if you're a language pedant who likes clarity, but a lot of categories and definitions are like this.
Your last sentence correctly points out the frailty of our definition of "species". However, this is not the only time our data has confounded our artificial, if often useful, definition of species boundaries.
I wonder what are the most visually, or structurally, or genetically, different animals that can still interbreed. Things like lions & tigers, polar bears & grizzlies, and zebras & horses, come to mind ... what else ?!
It's better than sci-fi, if you like strange creatures, dive into myrmecology.
edit: i might have that backwards
It is helpful to think of the whole colony as a singular organism as opposed to individuals, because our understanding of individual starts breaking down at these levels
The high-school version of evolution, playing out on an individual level, generation by generation (one baby giraffe, with a longer neck than another, reaches higher leaves and does better) gets the idea across, but evolution is about entire species not individuals, and for the most part any single genetic variation isn't going to have much impact, unless it's fatal.
In some sense the genetic feedback loop for ant population is designed in such a way that, it makes sense when looking at each ant colony as a singular organism
Unlike the giraffe, or elephants, who are individually capable of accumulating genetic variations.
Can't the organisms be viewed as individuals with a shared common goal.
The workers are involuntary but willing participants, in a grand scheme where the queens and males get to create new generations. But this is possible only if we anthropomorphise a lot.
because at the level of ants/bees I'm not even sure what "individual" even means.
But genetically they originate from the same individual, live for the betterment of the whole, and have very minor say in what happens to themselves or their genes. Much similar to cells in a human being does.
Create egg, remove nucleus of egg, replace nucleus of egg with one or two nuclei from stored sperm that initiate replication and growth of the other species from there (depending on the exact mechanism which it sounds like they're still figuring out).
Compared with fungus that creates zombie ants (this is a real thing - https://en.wikipedia.org/wiki/Ophiocordyceps_unilateralis) and birds that change their eggs to match those of other species (https://en.wikipedia.org/wiki/Brood_parasitism) it almost seems tame.
In this case, that happened. But if you do that, you can only expand as far as the other species expands. So you can expand further if you can find a way to keep the males of that species around with you.
This species does that by having a reproductive pathway that, if a queen is fertilized by that 'domesticated' species, the DNA of the 'host' species is removed from the eggs. So you get an ant that has none of the host's DNA. Except they do inherit the mitochondrial DNA (it always comes from the mother). The 'domesticated' males and the 'wild-type' males do look slightly different - it's not clear if this is because of the mitochondrial DNA or because they're raised differently or what.
I read someone compare the domesticated species to a 'superorganism organelle' - just like an archaea cell sucked up a bacteria to become a eukaryote, the host species sucked up the domesticated species to become some combination of both.
Wild to think what other crazy ways of living and makin babies must be out there that we haven't figured out yet.
More seriously, what those ants are doing is kind of unbelievable.
The hybrid worker ants should still share 75% of their DNA with the queen and therefore it makes sense for them to cooperate regardless of the source of DNA for their father.
The M. structor male clones however do not share any DNA with the queen presumably.
I wouldn't be surprised if further studies found that the M. structor genes were behaving selfishly. They must have some sort of aggressive mechanism for hijacking and evicting the queen genes for making clones.
Alternatively there could be a parasitic organism propagating through the reproductive procress.
> For M. ibericus, this adaptation ensures they have plenty of workers, which are responsible for many important tasks in a colony
I don't understand this part, though. It doesn't address why it is beneficial for the workers to be hybrids instead of pure M. ibericus. At some point M. ibericus lost the ability to make non-hybrid workers, but that must have happened after.
So there are roughly three evolutionary phases:
1. Hybridization is common, but largely inconsequential.
2. Hybrid queen elimination.
3. Male cloning.
[1] https://www.youtube.com/playlist?list=PL848F2368C90DDC3D
The egg came before the chicken.