8 ms·

To Lions, Zebras Are Mostly Gray

52 points by Hooke 11y ago

mintplant 11y ago
> The idea that its black-and-white coat might help it blend in rather than, say, stand out seems preposterous, but there are two ways in which this could work. First, the black stripes could match dark tree trunks while the white ones match shafts of light between the trunks. Alternatively, the stripes break up the zebra's outline, making it harder to identify as a juicy piece of horse-shaped steak. I always heard that it makes it difficult to discern individual zebras when they're gathered together in a herd, confusing their would-be predators.
- hammock 11y ago
  Check out razzle dazzle, visual camouflage for ships http://news.usni.org/2013/03/01/camouflaged-ships-an-illustrated-history http://news.usni.org/2013/03/01/camouflaged-ships-an-illustr...
  - theoh 11y ago
    Dazzle camouflage is fun but, at least originally, based on kind of specious logic. "I suddenly got the idea that since it was impossible to paint a ship so that she could not be seen by a submarine, the extreme opposite was the answer – in other words to paint her, not for low visibility, but in such a way as to break up her form and thus confuse a submarine officer as to the course on which she was heading." Thinking in opposites is an insidious trait that plays a big part in art and culture... but not in technology. The dazzle scheme sounds more reasonable in this account: "Wilkinson writes that “the painting of ships with the ‘Dazzle’ scheme is based on the general assumption that it is impossible to obtain invisibility at sea, especially where, as in the case of an attacking submarine, the object is seen against the sky with practically no sea to form a background…the only course open is to paint her in such a way as to deceive the attacker as to her size and course; this can only be done by extreme contrasts of colour and shapes which will so distort the vessel as to the symmetry and bulk.” (A Brush with Life)"
    - Retric 11y ago
      It's not based on opposites. Subs needed location and heading to sink a ship. They realized that gross location was out, so heading became the next target.
      - theoh 11y ago
        Norman Wilkinson, the developer of dazzle camouflage in the UK, had a flash of inspiration while sitting on a train that an "extreme opposite" approach was required. As someone who deals with artists a lot, I can only express my strong feeling that this was not a rigorous strategic insight. Creative, yes. In fact there appears to be no conclusive proof of the perceptual effectiveness of dazzle painting. Great for morale, though! I'm open to hearing alternative accounts.
        Retric 11y ago
        There was too much noise in the data to make real comparisons. Yes, 41% of the dazzle ships were struck amidships, compared to 52% of the uncamouflaged. However, dazzle ships where generally larger, so this may have been due to near misses becoming hits. IMO, dazzle would have only been useful when subs where under time pressure. However, it's a paint job so even a tiny difference would make this cost effective.
        KineticLensman 11y ago
        My understanding is that the camo was intended to confuse WW1 sub captains who were trying to compute torpedo firing solutions in their heads whil peering through the periscope. The target ship plainly would be highly visible but it's speed and heading would be obfuscated
    - marcosdumay 11y ago
      > Thinking in opposites is an insidious trait that plays a big part in art and culture... but not in technology. Why do you think it's rare in technology? To me it seems common in science, and, despite not instantly remembering any examples, does not sound far fetched in tech.
- murbard2 11y ago
  I've heard it, then did a safari in Bostwana, tested my ability to count zebras, and I can attest it is very difficult. I haven't performed the control experiment of counting horses, but I did notice that the stripes were seriously messing with my ability to detect edges.
EGreg 11y ago
All these "evolutionary arguments" -- this isn't real science. It's just a bunch of "just so" stories that are tested in some of the flimsiest ways (one phenomenon demonstrated to a statistically significant degree -- therefore that must have been "the reason for the evolutionary change"). Listen, tons of features that an animal has are not correlated so highly to survival as to make enough selective pressure to make that feature come to completely dominate a population. I am very skeptical of the widely "held" assumption otherwise. For example, lets say the human anorectal angle was specifically "evolved" for pooping while squatting. Is it a "just so" story or did the exact anorectal angle contribute SO MUCH to survival or reprosuction that it became the standard for bipedal humans? Consider just how much relative advantage with survival and replication any given feature must have in order to come to dominate ALL the other features that are competing in the population. And this is in just one area. During a single reproduction, there are tons of genetic and epigenetic variables that could be selected for, which determine different things. Why would a specific feature in a specific part of the body, that provides merely a minor improvement at any given time, come to completely replace all other genotype expressions? I have never seen a good analysis of this, just hopeful handwaving, especially in popular books like The Selfish Gene.
- facepalm 11y ago
  Just because many people make up evolutionary just so stories doesn't mean that there can not also be valid evolutionary explanations. If you just say "anorectal angle evolved so that people poop squatting" it is a just so story. To make it solid you have to show the context, history and so on. For example, why is it an advantage to be able to hold your poop in? A lot of things evolved out of serendipity and are not perfect, like those arteries going up and down the whole long neck of giraffes to bridge a short distance. But there are evolutionary explanations for it. As for features related to survival: I think phases with more and less pressure alternate. If you made a breakthrough, say you discovered skeletons, or invented the iPhone, for a while you may have such a big advantage that you can play around with lots of fancy variants. Eventually the rest of the world catches up, pressure gets higher and the less efficient variants get weeded out.
  - 11y ago
bauc 11y ago
I read some interesting research[1] where they modelled the movement of Zebra's and noticed that the stripes can create optical illusions by making them appear to be moving in the opposite direction to what they actually are. [1] http://www.bristol.ac.uk/biology/people/martin-j-how/pub/19703495 http://www.bristol.ac.uk/biology/people/martin-j-how/pub/197...
Jedd 11y ago
Three or four times in the past week, there's been front-page stories on HN that have reminded me of this. Rob Newman [0] (UK activist / comedian) has recently been considering evolution[1], particularly in response to the Selfish Gene approach to evolutionary biology. He's not a fan. Over the past couple of months his new radio show - the Entirely Accurate Encyclopaedia of Evolution[2] - has been broadcast in the UK on the BBC - a delightful combination of droll + biology/science in jokes + enlightenment. Mentioned partly because it deals with these kinds of claims in the abstract. Primarily because it deals with these kinds of claims specifically. In one episode he speaks about Cyclosa tremula [3] spider, who builds spider replicas from her prey - they are grey, while she is striped black & white (we finally return to the zebra analogy). When birds come to prey upon her, she bounces up and down quickly, turning herself grey - to match these replicas. He makes mention of a throw-away phrase from another paper on the subject, suggesting that Cylocsa tremula builds these facsimiles out of loneliness. The point being that we can never really know what mechanisms other organisms are using to evolve. [0] https://en.wikipedia.org/wiki/Robert_Newman_(comedian) [1] http://www.telegraph.co.uk/culture/comedy/10322813/Robert-Newman-The-universe-Richard-Dawkins-imagines-couldnt-exist-for-five-seconds.html [2] http://www.bbc.co.uk/programmes/b06jm72p [3] https://en.wikipedia.org/wiki/Cyclosa
- acqq 11y ago
  "What I think Dawkins has done is brought back a particularly virulent form of original sin. He’s actually a deeply religious thinker – ‘We are born selfish therefore let us try to teach altruism’, 'If your genes are selfish, you are.'" Both are surely not the quotes from Dawkins but Newman's own and wrong conclusions. Genes != whole animals (or humans). Especially the "interest" of the genes doesn't have to reflect in all aspects of the behavior to eliminate cooperation.
- goldbrick 11y ago
  This is a really scary movement, not only because he's blatantly straw-manning both Dawkins and Darwin, but because he's a populist without proper scientific credentials subtly pushing an agenda -- we could call him the Glenn Beck to Russell Brand's Joe Rogan. Nobody properly doing science ever suggests that we ever have all the answers and it frightens me that celebrities are so often given a podium of regressive anti-intellectualism on which to challenge the corpus of established scientific knowledge and even to misrepresent it.
rocky1138 11y ago
I feel like with a headline such as this, there should be a picture at the top of what a lion might see when it looks at a zebra.

52 points by Hooke 11y ago

> The idea that its black-and-white coat might help it blend in rather than, say, stand out seems preposterous, but there are two ways in which this could work. First, the black stripes could match dark tree trunks while the white ones match shafts of light between the trunks. Alternatively, the stripes break up the zebra's outline, making it harder to identify as a juicy piece of horse-shaped steak. I always heard that it makes it difficult to discern individual zebras when they're gathered together in a herd, confusing their would-be predators.

hammock 11y ago
Check out razzle dazzle, visual camouflage for ships http://news.usni.org/2013/03/01/camouflaged-ships-an-illustrated-history http://news.usni.org/2013/03/01/camouflaged-ships-an-illustr...
- theoh 11y ago
  Dazzle camouflage is fun but, at least originally, based on kind of specious logic. "I suddenly got the idea that since it was impossible to paint a ship so that she could not be seen by a submarine, the extreme opposite was the answer – in other words to paint her, not for low visibility, but in such a way as to break up her form and thus confuse a submarine officer as to the course on which she was heading." Thinking in opposites is an insidious trait that plays a big part in art and culture... but not in technology. The dazzle scheme sounds more reasonable in this account: "Wilkinson writes that “the painting of ships with the ‘Dazzle’ scheme is based on the general assumption that it is impossible to obtain invisibility at sea, especially where, as in the case of an attacking submarine, the object is seen against the sky with practically no sea to form a background…the only course open is to paint her in such a way as to deceive the attacker as to her size and course; this can only be done by extreme contrasts of colour and shapes which will so distort the vessel as to the symmetry and bulk.” (A Brush with Life)"
  - Retric 11y ago
    It's not based on opposites. Subs needed location and heading to sink a ship. They realized that gross location was out, so heading became the next target.
    - theoh 11y ago
      Norman Wilkinson, the developer of dazzle camouflage in the UK, had a flash of inspiration while sitting on a train that an "extreme opposite" approach was required. As someone who deals with artists a lot, I can only express my strong feeling that this was not a rigorous strategic insight. Creative, yes. In fact there appears to be no conclusive proof of the perceptual effectiveness of dazzle painting. Great for morale, though! I'm open to hearing alternative accounts.
      - Retric 11y ago
        There was too much noise in the data to make real comparisons. Yes, 41% of the dazzle ships were struck amidships, compared to 52% of the uncamouflaged. However, dazzle ships where generally larger, so this may have been due to near misses becoming hits. IMO, dazzle would have only been useful when subs where under time pressure. However, it's a paint job so even a tiny difference would make this cost effective.
      - KineticLensman 11y ago
        My understanding is that the camo was intended to confuse WW1 sub captains who were trying to compute torpedo firing solutions in their heads whil peering through the periscope. The target ship plainly would be highly visible but it's speed and heading would be obfuscated
  - marcosdumay 11y ago
    > Thinking in opposites is an insidious trait that plays a big part in art and culture... but not in technology. Why do you think it's rare in technology? To me it seems common in science, and, despite not instantly remembering any examples, does not sound far fetched in tech.
murbard2 11y ago
I've heard it, then did a safari in Bostwana, tested my ability to count zebras, and I can attest it is very difficult. I haven't performed the control experiment of counting horses, but I did notice that the stripes were seriously messing with my ability to detect edges.

EGreg 11y ago

All these "evolutionary arguments" -- this isn't real science. It's just a bunch of "just so" stories that are tested in some of the flimsiest ways (one phenomenon demonstrated to a statistically significant degree -- therefore that must have been "the reason for the evolutionary change"). Listen, tons of features that an animal has are not correlated so highly to survival as to make enough selective pressure to make that feature come to completely dominate a population. I am very skeptical of the widely "held" assumption otherwise. For example, lets say the human anorectal angle was specifically "evolved" for pooping while squatting. Is it a "just so" story or did the exact anorectal angle contribute SO MUCH to survival or reprosuction that it became the standard for bipedal humans? Consider just how much relative advantage with survival and replication any given feature must have in order to come to dominate ALL the other features that are competing in the population. And this is in just one area. During a single reproduction, there are tons of genetic and epigenetic variables that could be selected for, which determine different things. Why would a specific feature in a specific part of the body, that provides merely a minor improvement at any given time, come to completely replace all other genotype expressions? I have never seen a good analysis of this, just hopeful handwaving, especially in popular books like The Selfish Gene.

facepalm 11y ago
Just because many people make up evolutionary just so stories doesn't mean that there can not also be valid evolutionary explanations. If you just say "anorectal angle evolved so that people poop squatting" it is a just so story. To make it solid you have to show the context, history and so on. For example, why is it an advantage to be able to hold your poop in? A lot of things evolved out of serendipity and are not perfect, like those arteries going up and down the whole long neck of giraffes to bridge a short distance. But there are evolutionary explanations for it. As for features related to survival: I think phases with more and less pressure alternate. If you made a breakthrough, say you discovered skeletons, or invented the iPhone, for a while you may have such a big advantage that you can play around with lots of fancy variants. Eventually the rest of the world catches up, pressure gets higher and the less efficient variants get weeded out.
- 11y ago

bauc 11y ago

I read some interesting research[1] where they modelled the movement of Zebra's and noticed that the stripes can create optical illusions by making them appear to be moving in the opposite direction to what they actually are. [1] http://www.bristol.ac.uk/biology/people/martin-j-how/pub/19703495 http://www.bristol.ac.uk/biology/people/martin-j-how/pub/197...

Jedd 11y ago

Three or four times in the past week, there's been front-page stories on HN that have reminded me of this. Rob Newman [0] (UK activist / comedian) has recently been considering evolution[1], particularly in response to the Selfish Gene approach to evolutionary biology. He's not a fan. Over the past couple of months his new radio show - the Entirely Accurate Encyclopaedia of Evolution[2] - has been broadcast in the UK on the BBC - a delightful combination of droll + biology/science in jokes + enlightenment. Mentioned partly because it deals with these kinds of claims in the abstract. Primarily because it deals with these kinds of claims specifically. In one episode he speaks about Cyclosa tremula [3] spider, who builds spider replicas from her prey - they are grey, while she is striped black & white (we finally return to the zebra analogy). When birds come to prey upon her, she bounces up and down quickly, turning herself grey - to match these replicas. He makes mention of a throw-away phrase from another paper on the subject, suggesting that Cylocsa tremula builds these facsimiles out of loneliness. The point being that we can never really know what mechanisms other organisms are using to evolve. [0] https://en.wikipedia.org/wiki/Robert_Newman_(comedian) [1] http://www.telegraph.co.uk/culture/comedy/10322813/Robert-Newman-The-universe-Richard-Dawkins-imagines-couldnt-exist-for-five-seconds.html [2] http://www.bbc.co.uk/programmes/b06jm72p [3] https://en.wikipedia.org/wiki/Cyclosa

acqq 11y ago
"What I think Dawkins has done is brought back a particularly virulent form of original sin. He’s actually a deeply religious thinker – ‘We are born selfish therefore let us try to teach altruism’, 'If your genes are selfish, you are.'" Both are surely not the quotes from Dawkins but Newman's own and wrong conclusions. Genes != whole animals (or humans). Especially the "interest" of the genes doesn't have to reflect in all aspects of the behavior to eliminate cooperation.
goldbrick 11y ago
This is a really scary movement, not only because he's blatantly straw-manning both Dawkins and Darwin, but because he's a populist without proper scientific credentials subtly pushing an agenda -- we could call him the Glenn Beck to Russell Brand's Joe Rogan. Nobody properly doing science ever suggests that we ever have all the answers and it frightens me that celebrities are so often given a podium of regressive anti-intellectualism on which to challenge the corpus of established scientific knowledge and even to misrepresent it.

rocky1138 11y ago

I feel like with a headline such as this, there should be a picture at the top of what a lion might see when it looks at a zebra.