Zebras’ stripes discourage biting flies from landing
theatlantic.com
theatlantic.com
Evolution doesn’t care and has no sense of meaning, like in genetic algrotihms it is just about which patterns survive, which die and which remain as a funny annecdote with no practical effect.
From the article:
> Amanda Melin of the University of Calgary recently showed that lions and hyenas can’t even make out the stripes unless they get very close.
Sounds like it could still influence hunting as the predators have to get very close to make a kill
" By watching and filming the stable’s horses and zebras, the team confirmed that horseflies were much worse at alighting on the latter. The flies had no problem finding the zebras or approaching them, but couldn’t stick the landing. “You get a quarter as many landings,” Caro said. “The flies just can’t probe for a blood meal with the zebras.” "
I think the evolution angle relates to the question "Why did this trait evolve? What function does it serve?" with a potential Answer "It repels flies."
My critique was pointed at the wording. IMO it is not about why a trait evolved – there are many useless traits that envolved somewhere during special conditions and after these conditions change remain for a eternity or suddenly find a new usefulness in changed circumstances. This means pinpointing such a trait down to a single why is not a good representation of reality.
Are such observations valuable? For sure! Nature developed amazing strategies for all kind of things and not looking at these would be a waste.
I’d just be a bit more cautios with quick conclusions that involve meaning and answering why-questions, that’s all
Flies would be messing with the zebras ability to pass on their genes in some for for this trait to be selected for.
Evolution selects for traits correlated with successful reproduction. Correlation doesn't imply causation. All evolution can do is say "hey, things with this trait worked better, let's build more of these."
This nitpick is brought up each time someone makes an interesting observation. I can only image it is because people are trying to preempt intelligent design nonsense.
You are ofc right, it had no purpose when you talk generation to generation, the gradual tiny mutation each time did indeed serve no purpose.
But when you talk about the end product, the striped zebra, it is ok to say zebras (as the product of those millions of tiny iterations) might have evolved to discourage biting flies. Of course it could have been some other reason altogether, or a mixture of reasons but there is nothing wrong with the vocabulary, imo.
"By watching and filming the stable’s horses and zebras, the team confirmed that horseflies were much worse at alighting on the latter. The flies had no problem finding the zebras or approaching them, but couldn’t stick the landing. “You get a quarter as many landings,” Caro said. “The flies just can’t probe for a blood meal with the zebras.”
“When we looked at the videos, we found that the flies simply aren’t decelerating when they come in to the stripes,” Caro said. Either they miss and overshoot the zebras, or they bump into the hides and bounce off. Something’s clearly throwing them off, but the details are still a mystery. Caro said that they might treat the black stripes like a pair of trees, try to fly between them, and end up colliding with the white stripes. Alternatively, the stripes might mess with their optic flow—their sense of objects moving across their visual field.
https://www.techexplorist.com/body-painting-protects-bloodsu...
EDIT: but thinking about it more, nothing says multiple traits can't gain traction as a consequence of deadly pressure. I guess I never thought that much about evolution!
Imagine laying out the zebra rug for an Amazon drone delivery
Why is this fact never mentioned in this article, and did they do any analysis on how wearing a coat can affect CO2 levels around a horse's body?
[1]: https://journals.plos.org/plosone/article?id=10.1371/journal...
There is a reason the stripes are BLACK and WHITE. One absorbs the light and the other reflects, which in turn makes a slight difference of air temperature right above the skin surface. The difference of temperatures in certain areas cause (slight) differences in air pressure. This can cause a shallow "wind coat" around the Zebra (and more pronounced when the animal is moving) because of the air pressure deltas all over its skin. This helps Zebra's regulate body temperatures in some very hot climates.
So, a more scientifically oriented title should be: What do Stripes do for Zebras? Shoo away flies.
Zebras have stripes because their stripes shoo away flies, which helped previous generations of zebras who had stripes thrive and pass their genes forward. Why do zebras have stripes? Because they shoo flies away and evolution ensured that that helpful trait kept passing through descendants until every zebra had it as a dominant, visible trait.
No one ever said there had to be "someone" somewhere to paint zebras black and white, that's just you using anthropomorphized evolution as a straw man/entity.
Not necessarily. A trait may also be there simply because it's not actively harmful, or maybe because it's a useless side-effect of another trait that is beneficial.
It may be that zebras have stripes because they are not harmful enough to prevent them from passing their genes forward. (of course, in this particular case the flies hypothesis seems more likely).
You don't know that. The article doesn't even bother to test it.
They've observed that stripes lead to fewer horsefly landings. Interesting. I guess.
But, talking about evolution is a non sequitor. Show me the data where a zebra's fecundity is related to the number of horsefly bites it receives. There isn't any.
One can speculate about such things. But, if one wishes to be scientific, test to see if there is a measurable effect.
For all we know, zebras with MORE horsefly bites are MORE likely to reproduce. There simply is no data in the article one way or the other. So bringing up evolution is just mindless unscientific just-so-storytelling.
Doesn't it sound like such diseases are likely to alter a zebra's fecundity?
As far as the effect of 'such diseases' on a zebra's fecundity, I have no idea. For all we know, a feverish lethargic zebra is EASIER for a stallion to mount than a healthy zebra. Nobody knows.
The study, incidentally, did not deal with the types of flies accustomed to biting zebras. I have every reason to think a typical African biting fly would have no problem alighting on a zebra... it's what they do for a living.
So, there's nothing wrong with the title of "Why do Zebras have stripes [other than the obvious default non-answer 'because stripes are somehow good for them']? To Shoo Away Flies."
I.e. "why do they have Y" is "why" in the sense "what's the reason/cause of Y's continued existence".
Sure you can say Zebras have black and white stripes because their genes makes them express them in a certain way. However I could say they have stripes because it helps them shoo away flies. Someone else could say they have stripes because it makes them look pretty. Another person yet could say they only seem to have stripes because we can see those colors, but some other animals can't see them, so to us they have stripes. And then anyone could keep coming up with alternative answers. Even worse, you could ask why the mechanism that makes the Zebras have stripes works that way? And then why is that so. And then there's technically no end to it (just talk to any little kid). We just accept the first seemingly reasonable answer to a why question, and we've been trained it's rude or annoying to keep asking. But there's really no definitive answer, except whichever one you choose to accept.
There's some mechanism that makes stripes beneficial. Or perhaps there are multiple valid mechanisms - but in that case, one contributes (for example) 70% and the other 30%, and that can (with enough effort) be evaluated, and those mechanisms separated from the other alternative answers that are just guesses.
There are definitive answers. Perhaps they're hard to find out, perhaps they're hard to verify, perhaps for some aspects we'll not find out these definitive answers, but they certainly are there. You may reasonably choose that a particular answer isn't important enough to justify the resources needed to obtain that answer (and zebra stripes may well be a decent example for that), but giving in to the concept "there's really no definitive answer, except whichever one you choose to accept" is just shameful wilful ignorance. Reality is what exists no matter if you choose to accept it or not.
Is it? How do you know? You can't prove it. Reality to you is what you experience and you can never know what anyone else is experiencing. Reality is not objective, it depends on an observer. In fact if there are no observers, then there's no way to prove reality exists (and the concept wouldn't even make sense).
Even if there was an objective reality that was the same for all, "a reason" is a made up human concept, it is not a fundamental thing of nature/reality. You are even trying to define what a reason is in your comment.
So I would say, in this case, you calling other people willfully ignorant is just the way you deal with your reality to accept it and reject what the other person is trying to convey.
Doesn't look bad to me, and it's the same exact point.